- Email: [email protected]
Sintering and sliding wear studies of B4C-SiC composites
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
Contents lists available at ScienceDirect
International Journal of Refractory Metals & Hard Materials journal homepage: www.elsevier.com/locate/IJRMHM
Sintering and sliding wear studies of B4C-SiC composites Sonali Jamale, B.V. Manoj Kumar
⁎
TriboCeramics Laboratory, Department of Metallurgical and Materials Engineering, Indian Institute of Technology (IIT) Roorkee, Roorkee 247 667, India
ARTICLE INFO
ABSTRACT
Keywords: Boron carbide Silicon carbide Alumina Sliding wear
Dense boron carbide (B4C) – silicon carbide (SiC) composites were obtained by spark plasma sintering technique at 1800°C with 3 wt% and 6 wt% aluminium oxide (Al2O3) additives. Addition of sintering additives results in formation of aluminium silicate (Al2SiO5) liquid phase which accelerates sintering kinetics and helps in obtaining high density ~ 99%. Microstructures reveal uniformly distributed SiC particles in B4C matrix. Increase in alumina from 3 wt% to 6 wt% results in decrease in hardness from 35.1 ± 0.8 to 33.7 ± 0.9 GPa, and increase in fracture toughness from 5.9 ± 0.4 to 6.5 ± 0.4 MPam0.5. Using a ball-on-disk tribo tester under dry unlubricated conditions at 5, 10 or 15 N load, influence of alumina content on friction and wear properties of B4CSiC composites was investigated against SiC counterbody with a linear speed of 0.08 m/s for 60 min. The coefficient of friction (COF) increased from 0.25 to 0.65 with load, and the influence of alumina on frictional behaviour appeared to be negligible. With increase in load, wear volume of the composites increased from 7.5 × 10−2 mm3 to 16.1 × 10−2 mm3 for B4C-10 wt% SiC - 3 wt% Al2O3 and from 4.7 × 10−2 mm3 to 14.8 × 10−2 mm3 for B4C-10 wt% SiC - 6 wt% Al2O3 composites. Microcracking, abrasion and pull-outs contributed as major wear mechanisms of composites in selected wear conditions. The relation between wear behaviour and mechanical properties of sintered composites is discussed.
1. Introduction Design and development of high melting point ultra-hard materials is the most challenging task in processing and applications of ceramics. Boron carbide (B4C) is an attractive structural material due to the combination of its superior properties like high hardness, low density, high melting point (∼2540 °C), good chemical stability, high elastic modulus, high wear resistance. Such outstanding properties are required for the applications in the armour ceramics, sand blasting nozzles, neutron absorber, lapping agent, polishing of high-speed steel and carbide tool tips etc. [1,2]. The major limitation in the development of wide range of applications of boron carbide is its low sinterability and fracture toughness. Low self-diffusion coefficient demands high temperature for sintering of B4C powder to high density, while strong covalent bonding and lack of slip systems lead to high brittleness for the sintered B4C ceramics. Small amount of additives such as TiB2, CrB2, Al2O3, Y2O3, ZrO2, Fe3Al etc. are effective in improving the sintering kinetics and enhancing the mechanical properties of B4C [3–9]. Liquid phase formed with the additives facilitate sintering and is also responsible for increasing fracture toughness by changing the mode of fracture from transgranular to intergranular or combination [7–11]. Spark plasma sintering (SPS) has proved its ability for sintering boron
⁎
carbide to high density at low temperatures, short dwell time and high heating rate than conventional sintering [12–17]. Improved fracture toughness with high hardness and strength can only be achieved with a suitable combination of SPS processing parameters and additives [13]. In this regard, silicon carbide (SiC) is considered as an additive to improve sinterability as well as fracture toughness with less compromise on other mechanical properties of B4C. Malmal et al. [18] sintered B4C with 15 wt% SiC additive by SPS at 1700 °C and obtained a fracture toughness 5.7 MPa.m0.5 and hardness of 36.2 GPa. Filiz et al. [19] observed that the addition of yttria (Y2O3) improves densification of B4CSiC composites by SPS. Further densification of B4C-SiC is possible by adding small amount of low melting point additives like alumina (Al2O3). Increasing demand of boron carbide for wear resistant applications requires systematic investigation of its performance under different tribological mating conditions. Results acquired from the literature on friction and wear of boron carbide in different sliding wear conditions are outlined as follows: (1) Dense monolithic B4C ceramics were investigated in a various reciprocative sliding wear conditions against WC-Co cemented balls by Sonber et al. [20]. It is reported that the wear rate varied from
Corresponding author. E-mail address: [email protected] (B.V.M. Kumar).
https://doi.org/10.1016/j.ijrmhm.2019.105124 Received 12 June 2019; Received in revised form 27 September 2019; Accepted 3 October 2019 0263-4368/ © 2019 Elsevier Ltd. All rights reserved.
Please cite this article as: Sonali Jamale and B.V. Manoj Kumar, International Journal of Refractory Metals & Hard Materials, https://doi.org/10.1016/j.ijrmhm.2019.105124
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
S. Jamale and B.V.M. Kumar
between 20 °C to 600 °C Lin et al. [24] observed reduced friction and wear with the addition of CNT. The COF and wear rate fluctuated from 0.2 to 0.8 and 5 × 10−8 g/Nm to 50 × 10−8 g/Nm, respectively. (6) Ortiz et al. [25] sintered B4C ceramics to 95% density and studied wear behavior under lubrication with water, diesel and paraffine oil. Sliding wear rate was higher with water (8.6 × 10−7 mm3/Nm) than with diesel (6.0 × 10−8 mm3/Nm) and paraffin oil (2.9 × 10−8 mm3/Nm). From available studies, it is clear that the additives and lubrication helps in reducing wear but it is difficult to compare the scattered results in wear or friction due to differences in material processing, microstructural and mechanical characteristics as well as sliding test parameters. Furthermore, the influence of sintering additives on wear behavior of highly dense (≥96%) B4C ceramics is rarely reported. In the present study, the powder mixtures of B4C-10 wt% SiC-X Al2O3 (X: 3 wt% or 6 wt%) composites were sintered to high density (~99%), and tribological behaviour of sintered B4C-SiC composites in dry sliding wear conditions against SiC ceramics was studied. Alumina content and sliding loads were varied in this study, to observe their effects on sliding wear behaviour.
Fig. 1. Sintering profile of BSA3.
(2)
(3) (4)
(5)
1.6 × 10−6 to 4.7 × 10−6 mm3/Nm and the coefficient of friction (COF) varied from 0.1 to 0.2. Also, abrasive and tribochemical wear mechanisms were not observed on the worn surface. In a sliding wear study against chrome steel ball, Moshtaghioun et al. [21] observed lower wear rate for fully dense, coarse grained and harder B4C ceramics compared to higher wear rate of for 94.7% dense and fine grained and less harder B4C ceramics. In other study Zorzi et al. [22] reported B4C ceramics prepared with 4 wt% TiB2 additive showed 95.5% density and a minimum wear rate of 2.2 × 10−5 mm3/Nm. Sedlak et al. [23] reported wear rate decreased from 5 × 10−5 to 2.5 × 10−5 mm3/Nm with increase in graphene platelets content from 0 to 6 wt%. The COF varied from 0.34 to 0.58 with changing load from 5 to 50 N. In a sliding test on B4C ceramics at different temperatures ranging
2. Experimental methods 2.1. Materials and characterization Powder mixture batches of B4C, 10 wt% SiC and 3 wt% Al2O3 (designated as BSA3), and B4C, 10 wt% SiC and 6 wt% Al2O3 (designated as BSA6) were respectively mixed in a polypropylene jar using WC balls in toluene for 24 h. X-ray diffraction (XRD, D8 Discover, Brukeer AXS GmbH, Germany), was used to study phase analysis of powder mixtures. Both the mixtures were dried, sieved and then sintered at 1800 °C with heating rate of 150 °C/min for 10 min by spark plasma sintering (Dr. Sinter, SPS-625, Fuji Electronic Industrial Co. Ltd., Japan) at 40 MPa pressure in argon atmosphere.
Fig. 2. XRD patterns of BSA3 and BSA6.
2
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
S. Jamale and B.V.M. Kumar
Fig. 3. Typical SEM images of etched surfaces of (a) BSA3 and (b) BSA6 composites.
Fig. 4. SEM images of fracture surface of (a) BSA3 and (b)BSA6.
Fig. 5. Coefficient of friction (COF) vs. distance plots for (a) BSA3 and (b) BSA6 at different loads.
3
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
S. Jamale and B.V.M. Kumar
The length of cracks generated by Vickers indentation at 10 N for 10 s was measured to estimate fracture toughness (KIC) by the following Relation (1) [14,26]:
Table 1 The average steady state COF at different sliding loads for BSA3 and BSA6. Sample
5N
10 N
15 N
BSA3 BSA6
0.32 ± 0.09 0.38 ± 0.05
0.40 ± 0.19 0.47 ± 0.08
0.55 ± 0.20 0.62 ± 0.05
KIC = 0.0264 (Hv . a)
E Hv
0.4
(L
0.5)
(1)
where, Hv: hardness a: half diagonal length of indent L: total length of longest crack E: ’Elastic modulus 2.3. Sliding wear testing Tests were conducted on sintered BSA3 and BSA6 specimens of size ø10 mm x 5 mm against commercially available 10 mm SiC balls (~22GPa) using a ball on disk tribotester (TR-201E-M2, DUCOM, Bangalore, India) at ambient conditions (30 ± 5 °C and 35 ± 10% RH). Both the composite samples and counterbody were cleaned for 10 min by ultrasonic bath with acetone. To make a track of 3 mm diameter under three different loads: 5 N, 10 N and 15 N, SiC balls were fixed in a ball holder and the disk was rotated at 500 rpm rotational speed (0.08 m/s linear speed) for 60 min (counting 288 m of sliding distance). These sliding tests conditions results in generation of maximum Hertzian contact stresses (initial) ranging from 1.2 GPa to 1.8 GPa. An electronic sensor was used to obtain real time data of frictional force and COF was determined. Ten different locations were accounted for width and depth measurements of wear track, by surface profilometry (SJ400, Mitutoyo, Japan). The following Eq. (2) was used to determine the wear volume (Vd) in mm3:
Fig. 6. Typical surface profiles of wear track of BSA3 at 5 N and 15 N load against SiC ball.
(2)
Vd = 2 rWD where, r: radius of the circular wear scar W: width of the wear scar D: depth of the wear scar
The diameters of wear scars were measured by the ImageJ software. As per the following Eq. (3) average of wear scar diameter on ball (d) was used to determine the wear volume of ball (Vb):
Vb =
d4 64R
(3)
where, R: the radius of ball. Averaging of COF and wear volume was done after conducting three tests. Wear mechanisms were studied by SEM-EDS analysis and Raman spectroscopy (Renishaw inVia, UK). 3. Results and discussion 3.1. Phase analysis and microstructure
Fig. 7. Wear volume as function of load for BSA3 and BSA6.
Fig. 1 shows Z-axis displacement vs. temperature plot for sintering of BSA3. Displacement curve shows real-time shrinkage profile of the powder mixture during densification of the sample. Shrinkage occurred when temperature reached to 1500 °C, while sharp elevation is attributed to the generation of liquid phase aluminium silicate (Al2SiO5). In SiC-Al2O3 system, liquid phase of Al2SiO5 is known to form at 1600 °C (Eq. (4)).
2.2. Characterization of sintered composites Bulk densities of sintered BSA3 and BSA6 samples were determined using the Archimedes principle. X-ray diffractometry was used for the phase analysis of sintered samples. Microstructures of etched sample surfaces were studied using scanning electron microscopy (SEM Carl Zeiss EVO18, Germany) equipped with energy dispersive X-ray spectroscopy (EDS Oxford instruments x-act, UK). Hardness of sintered composites was determined by Vickers indentation at 3 N load for 10 s.
Al2 O3 + SiO2
Al2 SiO5
(4)
The liquid phase fills the pores, decreases particle-particle distance
4
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
S. Jamale and B.V.M. Kumar
Fig. 8. Typical SEM images of wear track of (a) BSA3 after sliding at 5 N (b) BSA3 after sliding at 15 N (c) BSA6 after sliding at 5 N (d) BSA6 after sliding at 15 N load. Dashed arrows indicate sliding direction.
and promotes densification of B4C [27]. Furthermore, displacement curve flattens out at 1800 °C indicating decline in densification rate. Relative densities obtained for BSA3 and BSA6 were 99.5% and 99.1%, respectively. Therefore, it can be stated that the selected conditions in spark plasma sintering were suitable for obtaining highly dense B4C-SiC composites. X- ray diffraction patterns of B4C-SiC composites BSA3 and BSA6 are shown in Fig. 2. Four crystallographic phases: B4C, SiC, Al2O3, Al2SiO5 are identified. The Al2SiO5 phase is present in both the composites but the peak intensity is higher in BSA6 than in BSA3 due to the availability of large Al2O3 content for the Reaction (4) to occur. SEM images of electrochemically etched microstructures of polished BSA3 and BSA6 are shown in Fig. 3. The microstructures reveal darker B4C grains of 2–4 μm size with uniform distribution of brighter SiC particles of 1–2 μm size. In addition, the small and bright phase observed along the grain boundaries or triple point junctions of B4C grains are believed to be alumina or aluminosilicate. Hardness values of 35.1 ± 0.8 GPa and 33.7 ± 0.9 GPa were respectively obtained for BSA3 and BSA6. Hardness decreased with increase in amount of relatively softer alumina additive in B4C ceramics [3]. By using the Palmqvist crack system [14], fracture toughness was estimated as 5.9 ± 0.4 MPa∙m1/2 for BSA3 and 6.5 ± 0.4 MPa∙m1/2 for BSA6. Increase in alumina content increases toughness of the B4C-SiC composite. The fracture surfaces of BAS3 and BSA6 (in Fig. 4) show dominant transgranular mode of fracture in both composites, indicating
stronger cohesion between B4C and SiC interface. The stronger interfacial cohesion is attributed to the less difference in thermal coefficients of expansion for B4C and SiC phases. 3.2. Frictional behaviour Fig. 5 shows COF vs. distance plots for both the samples. The COF plots indicate that steady state is achieved after sliding for 80–100 m distance. Fluctuations observed in COF plot indicate the presence of third body debris particles in the contact. The average COF values along with the standard deviations in the steady state (i.e. during last 200 m distance) at different loads are listed in Table 1. The average steady state COF varied between 0.32 and 0.62 with change in load or alumina content in the composite. At a given load, slightly higher average and lower standard deviation in steady state COF values are observed for BSA6. However, the average steady state COF significantly increased with increase in load for the composite with given alumina content. This suggests that the influence of load is significant compared to the influence of alumina content on friction of the composites in the selected conditions of sliding. 3.3. Wear results Typical surface profiles of wear tracks of BSA3 after sliding at 5 N and 15 N load are shown in Fig. 6. Average width and depth of track
5
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
S. Jamale and B.V.M. Kumar
Fig. 9. Representative SEM images demonstrating the wear surface characteristics of (a) BSA3 after sliding at 5 N (b) BSA3 after sliding at 15 N (c) BSA6 after sliding at 5 N (d) BSA6 after sliding at 15 N load.
oxide phase. The absence of SiO2 peak at 520 cm−1 is particularly indicated by a dashed arrow in Fig. 11. The observations from EDS and Raman analyses strongly indicate that the material removal was dominated by only mechanical fracture with negligible contribution from oxidative wear in sliding of the B4C-SiC composites in the selected sliding wear conditions. Almost circular scars are seen on worn surfaces of SiC balls counter body (see Fig. 12). The diameter of wear scars increased with load. Similarly, wear volume of SiC balls increased with load (see Fig. 13). Wear volume of SiC counterbody is comparable to composite disks (see Fig. 7), due to its low hardness. Wear debris particles from sliding contact of the BSA3 and BSA6 composite surfaces were collected, and SEM-EDS analysis was done. Fig. 14 shows SEM images of the debris particles obtained after wear of both the composites. The size of irregularly shaped debris particles varied from submicron to micron size. At higher load, large size debris particles were crushed into smaller ones.
found increased with increasing load, whereas less damage is observed at low load in both the composites. Wear volume of the investigated composites at different loads is shown in Fig. 7. Wear volume of the investigated composites varied from 7.5 × 10−2 mm3 to 16.1 × 10−2 mm3 for BSA3 and from 4.7 × 10−2 mm3 to 14.8 × 10−2 mm3 for BSA6. The observed increase in fracture with load is attributed to the increase in wear volume. It can be stated that the wear resistance of B4C-SiC composites significantly improved with increasing alumina additive content at low load (5 N). 3.4. Wear mechanisms Typical SEM images (in Fig. 8) show that the average width of the wear scar increased from 0.6 mm to 1.2 mm with increasing load. Grooves are formed due to the sliding of hard debris in the contact area and grains are pulled-out due to stress concentration with hard asperity contacts [28]. At load of 5 N, plastic grooving of the composite occurred with less fracture. With load increased to 15 N, grooving is not observed but dominant brittle fracture occurred. The mechanisms of the wear are clear at higher magnification images in Fig. 9. Severe grain fracture, pull-out and cracking due to abrasion are observed in both the composites, while severity of damage increased with the increase in load. Microcracks are found in perpendicular direction to the sliding direction. Sliding of ceramics in ambient conditions is often reported to result in the oxidation of the surface [28]. However, the presence of small amount of oxygen in EDS analysis of both unworn and worn regions of BSA3 (Fig. 10) indicates negligible oxidation of the contact surface. In addition, Raman analysis of worn BSA3 (presented in Fig. 11) also reveals the presence of only B4C and SiC phases, and the absence of any
3.5. Fracture induced wear In the current study, less amount of material is removed from less hard but tougher BSA6 compared to BSA3. Therefore, it can be said that the wear behaviour of B4C-SiC composites depends on the combination of hardness and fracture toughness. SEM images of BSA3 and BSA6 worn surfaces reveal significant contribution of fracture in material removal in sliding contacts. Following the lateral fracture model, wear volume (Vs) of the brittle solid sliding against sharp indenter can be expressed by Eq. (5) [28],
6
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
S. Jamale and B.V.M. Kumar
Fig. 10. SEM-EDS analysis on the unworn region and worn region of BSA3 after sliding at 5 N load.
(E). Fig. 15 displays that the experimentally measured wear volume is in proportion to the analytically calculated wear volume. It can be reconfirmed that wear volume increases with load for a given composite without any change in wear mechanism. SEM-EDS analysis and Raman analysis of worn surfaces also suggest fracture induced wear. The experimentally determined wear volume for BSA3 and BSA6 are closer at higher load conditions. Furthermore, minimum load required for the fracture of composite can be calculated by the Eq. (6) [28].
P* =
9
P8 1 KIC 2
×
5 H8
E H
4/5
S
KIc 3 KIc H
(6)
where β is the constant, g is the geometrical constant (~0.2) and η is a constant (~1). The incorporation of respective mechanical properties in eq. (6) indicates that BSA3 requires 0.65 N and BSA6 requires 1 N for the initiation of fracture. Therefore, the fracture of the composites in the sliding wear conditions at 5 N, 10 N and 15 N loads is reconfirmed. Summarizing, B4C-10 wt% SiC-3 wt% Al2O3 and B4C-10 wt% SiC6 wt% Al2O3 composites are worn out by fracture induced mechanical wear. The wear volume data further suggest that B4C-10 wt% SiC-6 wt% Al2O3 composite can be recommended for components subjected to sliding wear at low load (< 10 N).
Fig. 11. Raman spectroscopy analysis of worn and unworn surfaces of BSA3.
Vs =
54. 47 2g 4
4. Conclusions
(5)
High density (~99%) B4C-10 wt% SiC-3 wt% Al2O3 and B4C-10 wt% SiC-6 wt% Al2O3 were successfully sintered by spark plasma sintering.
where material independent constant is α, applied load (P), total sliding distance (S), hardness (H), fracture toughness (KIc) and elastic modulus 7
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
S. Jamale and B.V.M. Kumar
Fig. 12. Typical SEM images demonstrating the wear surface characteristics of SiC ball (a) after sliding against BSA3 at 10 N (b) after sliding against BSA3 15 N (c) after sliding against BSA6 10 N (d) after sliding against BSA6 15 N load.
The phase evolution, microstructural features and mechanical properties were studied. Effect of alumina content on friction and wear of B4CSiC composites in sliding contacts against commercially available counterbody of SiC balls at 5 N, 10 N and 15 N loads, was investigated using a ball on disk tribotester. The following are major conclusions: a) Alumina additive aids not only densification but also significantly affects mechanical properties of the sintered B4C-SiC composites. Hardness of the sintered composites decreased from 35.1 ± 0.8 GPa to 33.7 ± 0.9 GPa with increase in alumina content but fracture toughness increased from 5.9 ± 0.4 MPam0.5 to 6.5 ± 0.4 MPam0.5. b) In sliding against SiC ball, the average COF ranged between 0.25 and 0.65, and the wear volume ranged from 4.7 × 10−2 mm3 to 16.1 × 10−2 mm3, with change in load and alumina content. c) With increase in load, the average COF and wear volume of the composites increased. The influence of alumina on frictional behaviour was negligible, while the wear volume decreased with increasing alumina content at any load. A minimum wear volume of 4.7 × 10−2 mm3 obtained for B4C-10 wt% SiC- 6 wt% Al2O3 composite at 5 N load. d) Detailed study using SEM-EDS analysis and Raman analysis confirmed that the crack induced material removal was dominant for
Fig. 13. Wear volume of SiC counterbody slid against of BSA3 and BSA6.
8
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
S. Jamale and B.V.M. Kumar
Fig. 14. Typical SEM images of debris collected after sliding BSA3 at (a) 5 N (b) 15 N against SiC ball. fabricated by reaction hot pressing, J. Eur. Ceram. Soc. 23 (2003) 1123–1130. [8] I. Bogomol, H. Borodianska, T. Zhao, T. Nishimura, Y. Sakka, P. Loboda, O. Vasylkiv, A dense and tough (B4C–TiB2)–B4C ‘composite within a composite’ produced by spark plasma sintering, Scripta Material 71 (2014) 17–20. [9] P. He, S. Dong, Y. Kan, X. Zhang, Y. Ding, Microstructure and mechanical properties of B4C–TiB2 composites prepared by reaction hot pressing using Ti3SiC2 as additive, Ceram. Int. 42 (2016) 650–656. [10] S.S. Rehman, W. larssJi, S.A. Khan, M. Asif, Z. Fu, W. Wang, H. Wang, J. Zhang, Y. Wang, Microstructure and mechanical properties of B4C based ceramics with Fe3Al as sintering aid by spark plasma sintering, J. Eur. Ceram. Soc. 34 (2014) 2169–2175. [11] S. Yamada, K. Hiraob, Y. Yamauchib, S. Kanzakib, B4C-CrB2 composites with improved mechanical properties, J. Eur. Ceram. Soc. 23 (2003) 561–565. [12] S. Hayun, S. Kalabukhov, V. Ezersky, M.P. Dariel, N. Frage, Microstructural characterisation of spark plasma sintered boron carbide ceramic, Ceram. Int. 36 (2010) 451–457. [13] K. Sairam, J.K. Sonber, T.S.R.Ch. Murthy, C. Subramanian, R.K. Fotedar, P. Nanekar, R.C. Hubli, Influence of spark plasma sintering parameters on densification and mechanical properties of born carbide, J. Refract. Met. Hard Mater. 42 (2014) 185–192. [14] S. Hayuna, V. Paris, M.P. Dariel, N. Frage, E. Zaretzky, Static and dynamic mechanical properties of boron carbide processed by spark plasma sintering, J. Eur. Ceram. Soc. 29 (2009) 3395–3400. [15] X. Zhang, Z. Zhang, Y. Sun, M. Xiang, G. Wang, Y. Bai, J. Mu, H. Che, W. Wang, Preparation, microstructure and toughening mechanism of superhard ultrafinegrained boron carbide ceramics with outstanding fracture toughness, J All Comp 762 (2018) 125–132. [16] X. Li, D. jiang, J. zhang, Q. Lin, Z. Chen, Z. Huang, Densification behaviour and related phenomena of spark plasma sintered boron carbide, Ceram. Int. 40 (2014) 4359–4366. [17] B.M. Moshtaghioun, F.L. Cumbrera-Hernández, D. Gómez-García, S.D. BernardiMartín, A. Domínguez-Rodríguez, A. Monshi, M.H. Abbasi, Effect of spark plasma sintering parameters on microstructure and room-temperature hardness and toughness of fine-grained boron carbide (B4C), J. Eur. Ceram. Soc. 33 (2013) 361–369. [18] B.M. Moshtaghioun, A.L. Ortiz, D. Gómez-García, A. Domínguez-Rodríguez, Toughening of super-hard ultra-fine grained B4C densified by spark-plasma sintering via SiC addition, J. Eur. Ceram. Soc. 33 (2013) 1395–1401. [19] F.C. Sahin, B. Apak, I. Akin, H.E. Kanbur, D.H. Genckan, A. Turan, G. Goller, O. Yucel, Spark plasma sintering of B4C -SiC composites, Solid State Sci. 14 (2012) 1660–1663. [20] J.K. Sonber, P.K. Limaye, T.S.R.Ch. Murthy, K. Sairam, A. Nagaraj, N.L. Soni, R.K. Patel, J.K. Chakravartty, Tribological properties of boron carbide in sliding against WC ball, J. Refract. Met. Hard Mater. 51 (2015) 110–117. [21] B.M. Moshtaghioun, D. Gomez-Garcia, A. Dominguez-Rodriguez, R.I. Todd, Abrasive wear rate of boron carbide ceramics: influence of microstructural and mechanical aspects on their tribological response, J. Eur. Ceram. Soc. 36 (2016) 3925–3928. [22] J.E. Zorzi, C.A. Perottoni, J.A.H. da Jornada, Hardness and wear resistance of B4C ceramics prepared with several additives, Mater. Lett. 59 (2005) 2932–2935. [23] R. Sedlák, A. Kovalčíková, J. Balko, P. Rutkowski, A. Dubiel, D. Zientara, V. Girman, E. Múdra, J. Dusza, Effect of graphene platelets on tribological properties of boron carbide ceramic composites, J. Refract. Met. Hard Mater. 65 (2017) 57–63. [24] W. Lin, N. Fang, L. He, Wear properties of reaction sintered B4C composites, Adv. Mater. Res. 1662–8985 Vols. 152–153 (2010) 883–886 90. [25] A.L. Ortiz, V.M. Candelario, O. Borrero-López, F. Guiberteau, Sliding-wear resistance of pure near fully-dense B4C under lubrication with water, diesel fuel, and paraffin oil, J. Eur. Ceram. Soc. 38 (2018) 1158–1163. [26] Nihara, A fracture mechanics analysis of indentation-induced cracks in ceramics, J. Mater. Sci. 2 (1983) 221–223. [27] C.H. Lee, C.H. Kim, Pressureless sintering and related phenomena of Al2O3-doped B4C, J. Mater. Sci. 27 (1992) 6335–6340. [28] Basu, M. Kalin, Tribology of ceramics and composites, John Wiley & Sons, Inc, New Jersey, 2011.
Fig. 15. Wear volume against analytically calculated wear volume.
the investigated B4C-SiC composites in the selected sliding wear conditions. Declaration of Competing Interest Authors declare that they have no conflict of interest. This work has no involvement of the funding sources/agencies from the public, commercial and non-profit sections. There is no involvement of peer human resource other than mentioned, as well. Acknowledgement B4C powder received from Materials Processing & Corrosion Engineering Division, BARC, Mumbai, India. References [1] F. Thevenot, Boron carbide-A comprehensive review, J. Nucl. Mater. 152 (1988) 154–162. [2] A.K. Suri, C. Subramanian, J.K. Sonber, T.S.R.Ch. Murthy, Synthesis and consolidation of boron carbide review, Int Mat Rev 55 (2010) 4–40. [3] H.W. Kim, Y.H. Koh, H.E. Kim, Densification and mechanical properties of B4C with Al2O3 as sintering aid, J. Am. Ceram. Soc. 83 (2000) 2863–2865. [4] C. Sun, Y. Lin, Y. Wang, L. Zhu, Q. Jiang, Y. Miao, X. Chen, Effect of alumina addition on the densification of boron carbide ceramics prepared by spark plasma sintering technique, Ceram. Int. 40 (2014) 12723–12728. [5] C. Subramanian, T.K. Roy, T.S.R.Ch. Murthy, P. Sengupta, G.B. Kale, M.V. Krishnaiah, A.K. Suri, Effect of zirconia addition on pressureless sintering of boron carbide, Ceram. Int. 34 (2008) 1543–1549. [6] S. Yamada, K. Hirao, Y. Yamauchi, S. Kanzaki, Mechanical and electrical properties of B4C-CrB2 ceramics fabricated by liquid phase sintering, Ceram. Int. 29 (2003) 299–304. [7] S. Yamada, K. Hirao, Y. Yamauchi, S. Kanzaki, High strength B4C-TiB2 composites
9
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
S. Jamale and B.V.M. Kumar Sonali Jamale is currently pursuing her Ph.D. degree from Indian Institute of Technology (IIT) Roorkee. She obtained her master degree in nanotechnology from National Institute of Technology (NIT) Calicut in 2014. She received her bachelor's in mechanical engineering from S.R.T.M University Nanded. She works in understanding mechanical and tribological behaviour of ceramics.
B. V. Manoj Kumar is currently working as Associate Professor at the Department of Metallurgical and Materials Engineering, Indian Institute of Technology (IIT) Roorkee. Dr. Manoj works in understanding the microstructure mechanical property-wear relation of important ceramics/ cermets and composites prepared using advanced sintering techniques.
10
Contents lists available at ScienceDirect
International Journal of Refractory Metals & Hard Materials journal homepage: www.elsevier.com/locate/IJRMHM
Sintering and sliding wear studies of B4C-SiC composites Sonali Jamale, B.V. Manoj Kumar
⁎
TriboCeramics Laboratory, Department of Metallurgical and Materials Engineering, Indian Institute of Technology (IIT) Roorkee, Roorkee 247 667, India
ARTICLE INFO
ABSTRACT
Keywords: Boron carbide Silicon carbide Alumina Sliding wear
Dense boron carbide (B4C) – silicon carbide (SiC) composites were obtained by spark plasma sintering technique at 1800°C with 3 wt% and 6 wt% aluminium oxide (Al2O3) additives. Addition of sintering additives results in formation of aluminium silicate (Al2SiO5) liquid phase which accelerates sintering kinetics and helps in obtaining high density ~ 99%. Microstructures reveal uniformly distributed SiC particles in B4C matrix. Increase in alumina from 3 wt% to 6 wt% results in decrease in hardness from 35.1 ± 0.8 to 33.7 ± 0.9 GPa, and increase in fracture toughness from 5.9 ± 0.4 to 6.5 ± 0.4 MPam0.5. Using a ball-on-disk tribo tester under dry unlubricated conditions at 5, 10 or 15 N load, influence of alumina content on friction and wear properties of B4CSiC composites was investigated against SiC counterbody with a linear speed of 0.08 m/s for 60 min. The coefficient of friction (COF) increased from 0.25 to 0.65 with load, and the influence of alumina on frictional behaviour appeared to be negligible. With increase in load, wear volume of the composites increased from 7.5 × 10−2 mm3 to 16.1 × 10−2 mm3 for B4C-10 wt% SiC - 3 wt% Al2O3 and from 4.7 × 10−2 mm3 to 14.8 × 10−2 mm3 for B4C-10 wt% SiC - 6 wt% Al2O3 composites. Microcracking, abrasion and pull-outs contributed as major wear mechanisms of composites in selected wear conditions. The relation between wear behaviour and mechanical properties of sintered composites is discussed.
1. Introduction Design and development of high melting point ultra-hard materials is the most challenging task in processing and applications of ceramics. Boron carbide (B4C) is an attractive structural material due to the combination of its superior properties like high hardness, low density, high melting point (∼2540 °C), good chemical stability, high elastic modulus, high wear resistance. Such outstanding properties are required for the applications in the armour ceramics, sand blasting nozzles, neutron absorber, lapping agent, polishing of high-speed steel and carbide tool tips etc. [1,2]. The major limitation in the development of wide range of applications of boron carbide is its low sinterability and fracture toughness. Low self-diffusion coefficient demands high temperature for sintering of B4C powder to high density, while strong covalent bonding and lack of slip systems lead to high brittleness for the sintered B4C ceramics. Small amount of additives such as TiB2, CrB2, Al2O3, Y2O3, ZrO2, Fe3Al etc. are effective in improving the sintering kinetics and enhancing the mechanical properties of B4C [3–9]. Liquid phase formed with the additives facilitate sintering and is also responsible for increasing fracture toughness by changing the mode of fracture from transgranular to intergranular or combination [7–11]. Spark plasma sintering (SPS) has proved its ability for sintering boron
⁎
carbide to high density at low temperatures, short dwell time and high heating rate than conventional sintering [12–17]. Improved fracture toughness with high hardness and strength can only be achieved with a suitable combination of SPS processing parameters and additives [13]. In this regard, silicon carbide (SiC) is considered as an additive to improve sinterability as well as fracture toughness with less compromise on other mechanical properties of B4C. Malmal et al. [18] sintered B4C with 15 wt% SiC additive by SPS at 1700 °C and obtained a fracture toughness 5.7 MPa.m0.5 and hardness of 36.2 GPa. Filiz et al. [19] observed that the addition of yttria (Y2O3) improves densification of B4CSiC composites by SPS. Further densification of B4C-SiC is possible by adding small amount of low melting point additives like alumina (Al2O3). Increasing demand of boron carbide for wear resistant applications requires systematic investigation of its performance under different tribological mating conditions. Results acquired from the literature on friction and wear of boron carbide in different sliding wear conditions are outlined as follows: (1) Dense monolithic B4C ceramics were investigated in a various reciprocative sliding wear conditions against WC-Co cemented balls by Sonber et al. [20]. It is reported that the wear rate varied from
Corresponding author. E-mail address: [email protected] (B.V.M. Kumar).
https://doi.org/10.1016/j.ijrmhm.2019.105124 Received 12 June 2019; Received in revised form 27 September 2019; Accepted 3 October 2019 0263-4368/ © 2019 Elsevier Ltd. All rights reserved.
Please cite this article as: Sonali Jamale and B.V. Manoj Kumar, International Journal of Refractory Metals & Hard Materials, https://doi.org/10.1016/j.ijrmhm.2019.105124
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
S. Jamale and B.V.M. Kumar
between 20 °C to 600 °C Lin et al. [24] observed reduced friction and wear with the addition of CNT. The COF and wear rate fluctuated from 0.2 to 0.8 and 5 × 10−8 g/Nm to 50 × 10−8 g/Nm, respectively. (6) Ortiz et al. [25] sintered B4C ceramics to 95% density and studied wear behavior under lubrication with water, diesel and paraffine oil. Sliding wear rate was higher with water (8.6 × 10−7 mm3/Nm) than with diesel (6.0 × 10−8 mm3/Nm) and paraffin oil (2.9 × 10−8 mm3/Nm). From available studies, it is clear that the additives and lubrication helps in reducing wear but it is difficult to compare the scattered results in wear or friction due to differences in material processing, microstructural and mechanical characteristics as well as sliding test parameters. Furthermore, the influence of sintering additives on wear behavior of highly dense (≥96%) B4C ceramics is rarely reported. In the present study, the powder mixtures of B4C-10 wt% SiC-X Al2O3 (X: 3 wt% or 6 wt%) composites were sintered to high density (~99%), and tribological behaviour of sintered B4C-SiC composites in dry sliding wear conditions against SiC ceramics was studied. Alumina content and sliding loads were varied in this study, to observe their effects on sliding wear behaviour.
Fig. 1. Sintering profile of BSA3.
(2)
(3) (4)
(5)
1.6 × 10−6 to 4.7 × 10−6 mm3/Nm and the coefficient of friction (COF) varied from 0.1 to 0.2. Also, abrasive and tribochemical wear mechanisms were not observed on the worn surface. In a sliding wear study against chrome steel ball, Moshtaghioun et al. [21] observed lower wear rate for fully dense, coarse grained and harder B4C ceramics compared to higher wear rate of for 94.7% dense and fine grained and less harder B4C ceramics. In other study Zorzi et al. [22] reported B4C ceramics prepared with 4 wt% TiB2 additive showed 95.5% density and a minimum wear rate of 2.2 × 10−5 mm3/Nm. Sedlak et al. [23] reported wear rate decreased from 5 × 10−5 to 2.5 × 10−5 mm3/Nm with increase in graphene platelets content from 0 to 6 wt%. The COF varied from 0.34 to 0.58 with changing load from 5 to 50 N. In a sliding test on B4C ceramics at different temperatures ranging
2. Experimental methods 2.1. Materials and characterization Powder mixture batches of B4C, 10 wt% SiC and 3 wt% Al2O3 (designated as BSA3), and B4C, 10 wt% SiC and 6 wt% Al2O3 (designated as BSA6) were respectively mixed in a polypropylene jar using WC balls in toluene for 24 h. X-ray diffraction (XRD, D8 Discover, Brukeer AXS GmbH, Germany), was used to study phase analysis of powder mixtures. Both the mixtures were dried, sieved and then sintered at 1800 °C with heating rate of 150 °C/min for 10 min by spark plasma sintering (Dr. Sinter, SPS-625, Fuji Electronic Industrial Co. Ltd., Japan) at 40 MPa pressure in argon atmosphere.
Fig. 2. XRD patterns of BSA3 and BSA6.
2
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
S. Jamale and B.V.M. Kumar
Fig. 3. Typical SEM images of etched surfaces of (a) BSA3 and (b) BSA6 composites.
Fig. 4. SEM images of fracture surface of (a) BSA3 and (b)BSA6.
Fig. 5. Coefficient of friction (COF) vs. distance plots for (a) BSA3 and (b) BSA6 at different loads.
3
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
S. Jamale and B.V.M. Kumar
The length of cracks generated by Vickers indentation at 10 N for 10 s was measured to estimate fracture toughness (KIC) by the following Relation (1) [14,26]:
Table 1 The average steady state COF at different sliding loads for BSA3 and BSA6. Sample
5N
10 N
15 N
BSA3 BSA6
0.32 ± 0.09 0.38 ± 0.05
0.40 ± 0.19 0.47 ± 0.08
0.55 ± 0.20 0.62 ± 0.05
KIC = 0.0264 (Hv . a)
E Hv
0.4
(L
0.5)
(1)
where, Hv: hardness a: half diagonal length of indent L: total length of longest crack E: ’Elastic modulus 2.3. Sliding wear testing Tests were conducted on sintered BSA3 and BSA6 specimens of size ø10 mm x 5 mm against commercially available 10 mm SiC balls (~22GPa) using a ball on disk tribotester (TR-201E-M2, DUCOM, Bangalore, India) at ambient conditions (30 ± 5 °C and 35 ± 10% RH). Both the composite samples and counterbody were cleaned for 10 min by ultrasonic bath with acetone. To make a track of 3 mm diameter under three different loads: 5 N, 10 N and 15 N, SiC balls were fixed in a ball holder and the disk was rotated at 500 rpm rotational speed (0.08 m/s linear speed) for 60 min (counting 288 m of sliding distance). These sliding tests conditions results in generation of maximum Hertzian contact stresses (initial) ranging from 1.2 GPa to 1.8 GPa. An electronic sensor was used to obtain real time data of frictional force and COF was determined. Ten different locations were accounted for width and depth measurements of wear track, by surface profilometry (SJ400, Mitutoyo, Japan). The following Eq. (2) was used to determine the wear volume (Vd) in mm3:
Fig. 6. Typical surface profiles of wear track of BSA3 at 5 N and 15 N load against SiC ball.
(2)
Vd = 2 rWD where, r: radius of the circular wear scar W: width of the wear scar D: depth of the wear scar
The diameters of wear scars were measured by the ImageJ software. As per the following Eq. (3) average of wear scar diameter on ball (d) was used to determine the wear volume of ball (Vb):
Vb =
d4 64R
(3)
where, R: the radius of ball. Averaging of COF and wear volume was done after conducting three tests. Wear mechanisms were studied by SEM-EDS analysis and Raman spectroscopy (Renishaw inVia, UK). 3. Results and discussion 3.1. Phase analysis and microstructure
Fig. 7. Wear volume as function of load for BSA3 and BSA6.
Fig. 1 shows Z-axis displacement vs. temperature plot for sintering of BSA3. Displacement curve shows real-time shrinkage profile of the powder mixture during densification of the sample. Shrinkage occurred when temperature reached to 1500 °C, while sharp elevation is attributed to the generation of liquid phase aluminium silicate (Al2SiO5). In SiC-Al2O3 system, liquid phase of Al2SiO5 is known to form at 1600 °C (Eq. (4)).
2.2. Characterization of sintered composites Bulk densities of sintered BSA3 and BSA6 samples were determined using the Archimedes principle. X-ray diffractometry was used for the phase analysis of sintered samples. Microstructures of etched sample surfaces were studied using scanning electron microscopy (SEM Carl Zeiss EVO18, Germany) equipped with energy dispersive X-ray spectroscopy (EDS Oxford instruments x-act, UK). Hardness of sintered composites was determined by Vickers indentation at 3 N load for 10 s.
Al2 O3 + SiO2
Al2 SiO5
(4)
The liquid phase fills the pores, decreases particle-particle distance
4
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
S. Jamale and B.V.M. Kumar
Fig. 8. Typical SEM images of wear track of (a) BSA3 after sliding at 5 N (b) BSA3 after sliding at 15 N (c) BSA6 after sliding at 5 N (d) BSA6 after sliding at 15 N load. Dashed arrows indicate sliding direction.
and promotes densification of B4C [27]. Furthermore, displacement curve flattens out at 1800 °C indicating decline in densification rate. Relative densities obtained for BSA3 and BSA6 were 99.5% and 99.1%, respectively. Therefore, it can be stated that the selected conditions in spark plasma sintering were suitable for obtaining highly dense B4C-SiC composites. X- ray diffraction patterns of B4C-SiC composites BSA3 and BSA6 are shown in Fig. 2. Four crystallographic phases: B4C, SiC, Al2O3, Al2SiO5 are identified. The Al2SiO5 phase is present in both the composites but the peak intensity is higher in BSA6 than in BSA3 due to the availability of large Al2O3 content for the Reaction (4) to occur. SEM images of electrochemically etched microstructures of polished BSA3 and BSA6 are shown in Fig. 3. The microstructures reveal darker B4C grains of 2–4 μm size with uniform distribution of brighter SiC particles of 1–2 μm size. In addition, the small and bright phase observed along the grain boundaries or triple point junctions of B4C grains are believed to be alumina or aluminosilicate. Hardness values of 35.1 ± 0.8 GPa and 33.7 ± 0.9 GPa were respectively obtained for BSA3 and BSA6. Hardness decreased with increase in amount of relatively softer alumina additive in B4C ceramics [3]. By using the Palmqvist crack system [14], fracture toughness was estimated as 5.9 ± 0.4 MPa∙m1/2 for BSA3 and 6.5 ± 0.4 MPa∙m1/2 for BSA6. Increase in alumina content increases toughness of the B4C-SiC composite. The fracture surfaces of BAS3 and BSA6 (in Fig. 4) show dominant transgranular mode of fracture in both composites, indicating
stronger cohesion between B4C and SiC interface. The stronger interfacial cohesion is attributed to the less difference in thermal coefficients of expansion for B4C and SiC phases. 3.2. Frictional behaviour Fig. 5 shows COF vs. distance plots for both the samples. The COF plots indicate that steady state is achieved after sliding for 80–100 m distance. Fluctuations observed in COF plot indicate the presence of third body debris particles in the contact. The average COF values along with the standard deviations in the steady state (i.e. during last 200 m distance) at different loads are listed in Table 1. The average steady state COF varied between 0.32 and 0.62 with change in load or alumina content in the composite. At a given load, slightly higher average and lower standard deviation in steady state COF values are observed for BSA6. However, the average steady state COF significantly increased with increase in load for the composite with given alumina content. This suggests that the influence of load is significant compared to the influence of alumina content on friction of the composites in the selected conditions of sliding. 3.3. Wear results Typical surface profiles of wear tracks of BSA3 after sliding at 5 N and 15 N load are shown in Fig. 6. Average width and depth of track
5
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
S. Jamale and B.V.M. Kumar
Fig. 9. Representative SEM images demonstrating the wear surface characteristics of (a) BSA3 after sliding at 5 N (b) BSA3 after sliding at 15 N (c) BSA6 after sliding at 5 N (d) BSA6 after sliding at 15 N load.
oxide phase. The absence of SiO2 peak at 520 cm−1 is particularly indicated by a dashed arrow in Fig. 11. The observations from EDS and Raman analyses strongly indicate that the material removal was dominated by only mechanical fracture with negligible contribution from oxidative wear in sliding of the B4C-SiC composites in the selected sliding wear conditions. Almost circular scars are seen on worn surfaces of SiC balls counter body (see Fig. 12). The diameter of wear scars increased with load. Similarly, wear volume of SiC balls increased with load (see Fig. 13). Wear volume of SiC counterbody is comparable to composite disks (see Fig. 7), due to its low hardness. Wear debris particles from sliding contact of the BSA3 and BSA6 composite surfaces were collected, and SEM-EDS analysis was done. Fig. 14 shows SEM images of the debris particles obtained after wear of both the composites. The size of irregularly shaped debris particles varied from submicron to micron size. At higher load, large size debris particles were crushed into smaller ones.
found increased with increasing load, whereas less damage is observed at low load in both the composites. Wear volume of the investigated composites at different loads is shown in Fig. 7. Wear volume of the investigated composites varied from 7.5 × 10−2 mm3 to 16.1 × 10−2 mm3 for BSA3 and from 4.7 × 10−2 mm3 to 14.8 × 10−2 mm3 for BSA6. The observed increase in fracture with load is attributed to the increase in wear volume. It can be stated that the wear resistance of B4C-SiC composites significantly improved with increasing alumina additive content at low load (5 N). 3.4. Wear mechanisms Typical SEM images (in Fig. 8) show that the average width of the wear scar increased from 0.6 mm to 1.2 mm with increasing load. Grooves are formed due to the sliding of hard debris in the contact area and grains are pulled-out due to stress concentration with hard asperity contacts [28]. At load of 5 N, plastic grooving of the composite occurred with less fracture. With load increased to 15 N, grooving is not observed but dominant brittle fracture occurred. The mechanisms of the wear are clear at higher magnification images in Fig. 9. Severe grain fracture, pull-out and cracking due to abrasion are observed in both the composites, while severity of damage increased with the increase in load. Microcracks are found in perpendicular direction to the sliding direction. Sliding of ceramics in ambient conditions is often reported to result in the oxidation of the surface [28]. However, the presence of small amount of oxygen in EDS analysis of both unworn and worn regions of BSA3 (Fig. 10) indicates negligible oxidation of the contact surface. In addition, Raman analysis of worn BSA3 (presented in Fig. 11) also reveals the presence of only B4C and SiC phases, and the absence of any
3.5. Fracture induced wear In the current study, less amount of material is removed from less hard but tougher BSA6 compared to BSA3. Therefore, it can be said that the wear behaviour of B4C-SiC composites depends on the combination of hardness and fracture toughness. SEM images of BSA3 and BSA6 worn surfaces reveal significant contribution of fracture in material removal in sliding contacts. Following the lateral fracture model, wear volume (Vs) of the brittle solid sliding against sharp indenter can be expressed by Eq. (5) [28],
6
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
S. Jamale and B.V.M. Kumar
Fig. 10. SEM-EDS analysis on the unworn region and worn region of BSA3 after sliding at 5 N load.
(E). Fig. 15 displays that the experimentally measured wear volume is in proportion to the analytically calculated wear volume. It can be reconfirmed that wear volume increases with load for a given composite without any change in wear mechanism. SEM-EDS analysis and Raman analysis of worn surfaces also suggest fracture induced wear. The experimentally determined wear volume for BSA3 and BSA6 are closer at higher load conditions. Furthermore, minimum load required for the fracture of composite can be calculated by the Eq. (6) [28].
P* =
9
P8 1 KIC 2
×
5 H8
E H
4/5
S
KIc 3 KIc H
(6)
where β is the constant, g is the geometrical constant (~0.2) and η is a constant (~1). The incorporation of respective mechanical properties in eq. (6) indicates that BSA3 requires 0.65 N and BSA6 requires 1 N for the initiation of fracture. Therefore, the fracture of the composites in the sliding wear conditions at 5 N, 10 N and 15 N loads is reconfirmed. Summarizing, B4C-10 wt% SiC-3 wt% Al2O3 and B4C-10 wt% SiC6 wt% Al2O3 composites are worn out by fracture induced mechanical wear. The wear volume data further suggest that B4C-10 wt% SiC-6 wt% Al2O3 composite can be recommended for components subjected to sliding wear at low load (< 10 N).
Fig. 11. Raman spectroscopy analysis of worn and unworn surfaces of BSA3.
Vs =
54. 47 2g 4
4. Conclusions
(5)
High density (~99%) B4C-10 wt% SiC-3 wt% Al2O3 and B4C-10 wt% SiC-6 wt% Al2O3 were successfully sintered by spark plasma sintering.
where material independent constant is α, applied load (P), total sliding distance (S), hardness (H), fracture toughness (KIc) and elastic modulus 7
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
S. Jamale and B.V.M. Kumar
Fig. 12. Typical SEM images demonstrating the wear surface characteristics of SiC ball (a) after sliding against BSA3 at 10 N (b) after sliding against BSA3 15 N (c) after sliding against BSA6 10 N (d) after sliding against BSA6 15 N load.
The phase evolution, microstructural features and mechanical properties were studied. Effect of alumina content on friction and wear of B4CSiC composites in sliding contacts against commercially available counterbody of SiC balls at 5 N, 10 N and 15 N loads, was investigated using a ball on disk tribotester. The following are major conclusions: a) Alumina additive aids not only densification but also significantly affects mechanical properties of the sintered B4C-SiC composites. Hardness of the sintered composites decreased from 35.1 ± 0.8 GPa to 33.7 ± 0.9 GPa with increase in alumina content but fracture toughness increased from 5.9 ± 0.4 MPam0.5 to 6.5 ± 0.4 MPam0.5. b) In sliding against SiC ball, the average COF ranged between 0.25 and 0.65, and the wear volume ranged from 4.7 × 10−2 mm3 to 16.1 × 10−2 mm3, with change in load and alumina content. c) With increase in load, the average COF and wear volume of the composites increased. The influence of alumina on frictional behaviour was negligible, while the wear volume decreased with increasing alumina content at any load. A minimum wear volume of 4.7 × 10−2 mm3 obtained for B4C-10 wt% SiC- 6 wt% Al2O3 composite at 5 N load. d) Detailed study using SEM-EDS analysis and Raman analysis confirmed that the crack induced material removal was dominant for
Fig. 13. Wear volume of SiC counterbody slid against of BSA3 and BSA6.
8
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
S. Jamale and B.V.M. Kumar
Fig. 14. Typical SEM images of debris collected after sliding BSA3 at (a) 5 N (b) 15 N against SiC ball. fabricated by reaction hot pressing, J. Eur. Ceram. Soc. 23 (2003) 1123–1130. [8] I. Bogomol, H. Borodianska, T. Zhao, T. Nishimura, Y. Sakka, P. Loboda, O. Vasylkiv, A dense and tough (B4C–TiB2)–B4C ‘composite within a composite’ produced by spark plasma sintering, Scripta Material 71 (2014) 17–20. [9] P. He, S. Dong, Y. Kan, X. Zhang, Y. Ding, Microstructure and mechanical properties of B4C–TiB2 composites prepared by reaction hot pressing using Ti3SiC2 as additive, Ceram. Int. 42 (2016) 650–656. [10] S.S. Rehman, W. larssJi, S.A. Khan, M. Asif, Z. Fu, W. Wang, H. Wang, J. Zhang, Y. Wang, Microstructure and mechanical properties of B4C based ceramics with Fe3Al as sintering aid by spark plasma sintering, J. Eur. Ceram. Soc. 34 (2014) 2169–2175. [11] S. Yamada, K. Hiraob, Y. Yamauchib, S. Kanzakib, B4C-CrB2 composites with improved mechanical properties, J. Eur. Ceram. Soc. 23 (2003) 561–565. [12] S. Hayun, S. Kalabukhov, V. Ezersky, M.P. Dariel, N. Frage, Microstructural characterisation of spark plasma sintered boron carbide ceramic, Ceram. Int. 36 (2010) 451–457. [13] K. Sairam, J.K. Sonber, T.S.R.Ch. Murthy, C. Subramanian, R.K. Fotedar, P. Nanekar, R.C. Hubli, Influence of spark plasma sintering parameters on densification and mechanical properties of born carbide, J. Refract. Met. Hard Mater. 42 (2014) 185–192. [14] S. Hayuna, V. Paris, M.P. Dariel, N. Frage, E. Zaretzky, Static and dynamic mechanical properties of boron carbide processed by spark plasma sintering, J. Eur. Ceram. Soc. 29 (2009) 3395–3400. [15] X. Zhang, Z. Zhang, Y. Sun, M. Xiang, G. Wang, Y. Bai, J. Mu, H. Che, W. Wang, Preparation, microstructure and toughening mechanism of superhard ultrafinegrained boron carbide ceramics with outstanding fracture toughness, J All Comp 762 (2018) 125–132. [16] X. Li, D. jiang, J. zhang, Q. Lin, Z. Chen, Z. Huang, Densification behaviour and related phenomena of spark plasma sintered boron carbide, Ceram. Int. 40 (2014) 4359–4366. [17] B.M. Moshtaghioun, F.L. Cumbrera-Hernández, D. Gómez-García, S.D. BernardiMartín, A. Domínguez-Rodríguez, A. Monshi, M.H. Abbasi, Effect of spark plasma sintering parameters on microstructure and room-temperature hardness and toughness of fine-grained boron carbide (B4C), J. Eur. Ceram. Soc. 33 (2013) 361–369. [18] B.M. Moshtaghioun, A.L. Ortiz, D. Gómez-García, A. Domínguez-Rodríguez, Toughening of super-hard ultra-fine grained B4C densified by spark-plasma sintering via SiC addition, J. Eur. Ceram. Soc. 33 (2013) 1395–1401. [19] F.C. Sahin, B. Apak, I. Akin, H.E. Kanbur, D.H. Genckan, A. Turan, G. Goller, O. Yucel, Spark plasma sintering of B4C -SiC composites, Solid State Sci. 14 (2012) 1660–1663. [20] J.K. Sonber, P.K. Limaye, T.S.R.Ch. Murthy, K. Sairam, A. Nagaraj, N.L. Soni, R.K. Patel, J.K. Chakravartty, Tribological properties of boron carbide in sliding against WC ball, J. Refract. Met. Hard Mater. 51 (2015) 110–117. [21] B.M. Moshtaghioun, D. Gomez-Garcia, A. Dominguez-Rodriguez, R.I. Todd, Abrasive wear rate of boron carbide ceramics: influence of microstructural and mechanical aspects on their tribological response, J. Eur. Ceram. Soc. 36 (2016) 3925–3928. [22] J.E. Zorzi, C.A. Perottoni, J.A.H. da Jornada, Hardness and wear resistance of B4C ceramics prepared with several additives, Mater. Lett. 59 (2005) 2932–2935. [23] R. Sedlák, A. Kovalčíková, J. Balko, P. Rutkowski, A. Dubiel, D. Zientara, V. Girman, E. Múdra, J. Dusza, Effect of graphene platelets on tribological properties of boron carbide ceramic composites, J. Refract. Met. Hard Mater. 65 (2017) 57–63. [24] W. Lin, N. Fang, L. He, Wear properties of reaction sintered B4C composites, Adv. Mater. Res. 1662–8985 Vols. 152–153 (2010) 883–886 90. [25] A.L. Ortiz, V.M. Candelario, O. Borrero-López, F. Guiberteau, Sliding-wear resistance of pure near fully-dense B4C under lubrication with water, diesel fuel, and paraffin oil, J. Eur. Ceram. Soc. 38 (2018) 1158–1163. [26] Nihara, A fracture mechanics analysis of indentation-induced cracks in ceramics, J. Mater. Sci. 2 (1983) 221–223. [27] C.H. Lee, C.H. Kim, Pressureless sintering and related phenomena of Al2O3-doped B4C, J. Mater. Sci. 27 (1992) 6335–6340. [28] Basu, M. Kalin, Tribology of ceramics and composites, John Wiley & Sons, Inc, New Jersey, 2011.
Fig. 15. Wear volume against analytically calculated wear volume.
the investigated B4C-SiC composites in the selected sliding wear conditions. Declaration of Competing Interest Authors declare that they have no conflict of interest. This work has no involvement of the funding sources/agencies from the public, commercial and non-profit sections. There is no involvement of peer human resource other than mentioned, as well. Acknowledgement B4C powder received from Materials Processing & Corrosion Engineering Division, BARC, Mumbai, India. References [1] F. Thevenot, Boron carbide-A comprehensive review, J. Nucl. Mater. 152 (1988) 154–162. [2] A.K. Suri, C. Subramanian, J.K. Sonber, T.S.R.Ch. Murthy, Synthesis and consolidation of boron carbide review, Int Mat Rev 55 (2010) 4–40. [3] H.W. Kim, Y.H. Koh, H.E. Kim, Densification and mechanical properties of B4C with Al2O3 as sintering aid, J. Am. Ceram. Soc. 83 (2000) 2863–2865. [4] C. Sun, Y. Lin, Y. Wang, L. Zhu, Q. Jiang, Y. Miao, X. Chen, Effect of alumina addition on the densification of boron carbide ceramics prepared by spark plasma sintering technique, Ceram. Int. 40 (2014) 12723–12728. [5] C. Subramanian, T.K. Roy, T.S.R.Ch. Murthy, P. Sengupta, G.B. Kale, M.V. Krishnaiah, A.K. Suri, Effect of zirconia addition on pressureless sintering of boron carbide, Ceram. Int. 34 (2008) 1543–1549. [6] S. Yamada, K. Hirao, Y. Yamauchi, S. Kanzaki, Mechanical and electrical properties of B4C-CrB2 ceramics fabricated by liquid phase sintering, Ceram. Int. 29 (2003) 299–304. [7] S. Yamada, K. Hirao, Y. Yamauchi, S. Kanzaki, High strength B4C-TiB2 composites
9
International Journal of Refractory Metals & Hard Materials xxx (xxxx) xxxx
S. Jamale and B.V.M. Kumar Sonali Jamale is currently pursuing her Ph.D. degree from Indian Institute of Technology (IIT) Roorkee. She obtained her master degree in nanotechnology from National Institute of Technology (NIT) Calicut in 2014. She received her bachelor's in mechanical engineering from S.R.T.M University Nanded. She works in understanding mechanical and tribological behaviour of ceramics.
B. V. Manoj Kumar is currently working as Associate Professor at the Department of Metallurgical and Materials Engineering, Indian Institute of Technology (IIT) Roorkee. Dr. Manoj works in understanding the microstructure mechanical property-wear relation of important ceramics/ cermets and composites prepared using advanced sintering techniques.
10