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Effect of heat treatment and TiN coating on AISI O1 cold work tool steel
Materials Today: Proceedings xxx (xxxx) xxx
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Effect of heat treatment and TiN coating on AISI O1 cold work tool steel Sunil Kumar ⇑, Saikat Ranjan Maity, Lokeswar Patnaik Department of Mechanical Engineering, National Institute of Technology Silchar, Assam 788010, India
a r t i c l e
i n f o
Article history: Received 20 December 2019 Accepted 27 December 2019 Available online xxxx Keywords: AISI O1 Tool Steel Heat Treatment TiN coating XRD EDS
a b s t r a c t The effect of heat treatment and TiN coating on AISI O1 cold work tool steel was investigated. Microstructural and phase analysis was done using optical microscope and X-Ray diffraction. The crystalline size of heat treated and TiN coating were observed to be 5.4 lm and 0.05 lm respectively. Elemental composition was examined using Energy-dispersive spectroscopy. Mechanical and wear properties of substrate was analyzed using Hystron TI 950 Triboindentater. TiN coated substrate exhibited higher hardness (19.6 GPa) and elastic modulus (289 GPa) than the heat treated substrate. Hardness and elastic modulus post TiN coating was increased by 308% and 53.7% respectively. Lower specific wear rate was observed for TiN coated substrate (1.8 10–12 m2N1) than heat treated substrate (2.7 10–15 m2N1). In summary, TiN coated substrate has higher mechanical and wear resistance compared to heat treated substrate. Ó 2020 Elsevier Ltd. All rights reserved. Selection and of the scientific committee of the 10th International Conference of Materials Processing and Characterization.
1. Introduction Tool steel needs high strength with good toughness to resist the penetration and exhibit better shock absorbing capacity. Heat treatment along with quenching and tempering is playing a vital role to achieve these combined properties [1]. Low percentage of austenite was retained after heat treatment which is known as retained austenite, it is soft in nature which causes reduction in product life. Retained austenite have to transform into martensitic structure to accommodate the tooling requirements. The new transformed martensite has needle like structure which is excessive brittle in nature and leads to dimensional instability and it is known as retained martensite. Therefore, controlled transformation (quenching) is required to avoid the formation of retained martensite to improve the wear resistance of tool steel [2]. Wear resistance can be improve using various surface treatment processes where microstructural and chemical composition of surface can be modified. This is achieved by transformation hardening which improves the surface as well as volumetric properties of tool steel [3]. Wear resistance of tool steel can be improved using ceramic coatings like TiN, TiAlN, AlCrN and TiCrN etc. Titanium nitride
(TiN) coating is widely used in tooling industries for its lower coefficient of friction and excellent resistance to wear and corrosion [4–6]. TiN coating is deposited by cathode arc deposition using physical vapour deposition or chemical vapour deposition technique, where coating thickness upto 10 mm can be achieved due to lower coefficient of friction. Literature suggests that resistance to corrosion decreases with increasing coating thickness [7–10]. Metallic or non-metallic matrix with dense composite and fine scattered ceramic phase can be achieved using reactive plasma spraying (RPS) technique which also improves the wear property [11]. Precipitation of titanium and nitrogen before solidification is necessary for the TiN coating to attain higher strength and resistance to wear [12–13]. In this work, microstructural, mechanical and wear properties of heat treated (HT) and TiN coated AISI O1 cold work tool steel was studied and compared with as-O1 tool steel. Microstructural analysis was done for all the substrate using optical microscope (OM) and X-Ray diffraction (XRD). Furthermore, energydispersive spectroscopy (EDS) was used to analyze the elemental composition of the substrates. Finally, Nanoindentation and nanoscratch test was performed to examine the mechanical and wear properties of the substrates.
⇑ Corresponding author. E-mail address: [email protected] (S. Kumar). https://doi.org/10.1016/j.matpr.2019.12.367 2214-7853/Ó 2020 Elsevier Ltd. All rights reserved. Selection and of the scientific committee of the 10th International Conference of Materials Processing and Characterization.
Please cite this article as: S. Kumar, S. R. Maity and L. Patnaik, Effect of heat treatment and TiN coating on AISI O1 cold work tool steel, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.367
2
S. Kumar et al. / Materials Today: Proceedings xxx (xxxx) xxx
2. Material and method 2.1. Material AISI O1 cold work tool steel of 30 mm diameter was used as base metal (substrate) for this study. Chemical composition of the steel is tabulated in Table 1. Substrate was machined to maintain the size of Ø30 mm and thickness 10 mm. Substrate were heat treated according to ASM standards of hardening [14].
indenter. Indentation hardness and elastic modulus was obtained using Oliver and Pharr method [15]. 6000 mN load was applied at a rate of 600 mN/s during loading. Peak load was kept hold for 2 s and then released at 600 mN/s load during unloading. Total twenty number of indentations were performed to record the average value. Hardness and elastic modulus was calculated using Eqs. (2) and (3) respectively.
Hs ¼
Pmax Aðhc Þ
ð2Þ
2.2. Thin film coating
Where hc is contact depth and A is contact area. Pmax is the maximum load applied during indentation.
The heat treated samples were coated with TiN coating at Orlikon Balzer Coating India Ltd, Chennai using cathode arc deposition. The coating parameters are tabulated in Table 2.
1 ð1 v 2 Þ ð1 v 2i Þ þ ¼ Er E Ei
2.3. Thin film characterization Optical microscope (Dewinter optical, Inc.) was used to analyses the microstructure of as-O1 and HT-O1 tool steel. Substrates were polished with sand paper grit of 100, 250, 400, 800, 1000 and 1400 to achieve 2 mm of surface roughness. Polishing was done using diamond paste (size of 3 mm) on a rotating disc polishing machine. Finally, the substrates were cleaned with alcohol and dried using a blower. Prior to microscopic analysis the samples were etched with nital (solution of ethanol and HNO3). Phase of the crystal was analyzed using X-Ray diffraction (PANalytical B.V.) with CuKa radiation at accelerated potential of 40 KV. The diffraction angle ranges from 20°-80° at a speed 0.08 °/min. Each substrate was analyzed over a scanning region of 20 20 mm2. The crystalline size of substrate was calculated using Scherer Eq. (1). Elemental composition of HT-O1 tool steel and TiN coating were analyzed by EDS (Zeiss Supra 55-VP FEGSEM, Germany).
18Kk L ¼ qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 p b xCOSh
ð1Þ
Where K is the fatigue factor of the grains, k represents the wavelength of CuKa, b represents diffraction peak width at half height, x represents FWHM and h represents Bragg angle.
ð3Þ
E and v is elastic modulus and Poisson’s ratio the sample respectively, Ei is elastic modulus of indenter (1141 GPa) and v i is Poisson’s ratio of indenter (0.07). Nanoscratch was conducted with fixed load of 6000 mN for 10 mm scratch length. Image of scratch track was recorded using scanning probe microscopy (SPM). Scratch hardness and specific wear rate were calculated using Eq. (4) and Eq. (5) respectively.
Hs ¼ 2:31
PN w2
ð4Þ
Where P N is the maximum normal force applied to the indenter during scratch and w is width of scratch track.
K¼
V PL
ð5Þ
Where K is specific wear rate of the scratch (m2N1), V is volume of scratch (m3) obtained using Eq. (6), P is normal load (N) and L is total sliding distance (m).
V¼
1 2 cos ð70:3Þd l 2
ð6Þ
d and l are the depth (nm) and length of scratch wear track (m) respectively. 3. Results and discussion 3.1. Microstructural and XRD analysis
2.4. Nanoindentation and nanoscratch characterizations Hystron Ti950 Tribometer was used to performed nanoindentation and scratch test with 100 nm tip radius of Berkovich shaped
Table 1 Chemical composition of AISI O1 tool steel. Elements
C
Mn
Cr
W
V
Weight %
0.95
1.10
0.60
0.60
0.10
Table 2 Coating parameter for TiN coating. Coating parameters
Conditions
Etching duration Nitrogen (N2) gas flow rate Argon gas flow rate Planetary rotating speed Cathode amperage hour (Ah) Coating temperature Chamber pressure Coating bias voltage range Deposition time
30 min 4.67 106 m3/s 0.8 106 m3/s 2 rpm 600 Ah <500 °C 6 10-9 bar 50 V–600 V 4h
Microstructural and phase analysis of as-O1, HT-O1 and TiN coated O1 tool steel was analyzed by using OM and XRD as shown in Fig. 1. Principal of this characterization was to impart the nature, morphology, distribution of carbide particles and amount of austenite retained in the crystal. Fig. 1(b) depicts that carbide particles are present in the form of tempered martensite after the heat treatment. XRD pattern of HT-O1 steel confirms the presence of tempered martensite. Similar observations can be found elsewhere [16–18]. The quantity of fine carbide decreases with increasing austenitizing temperature. In addition to this, at higher austenitizing temperature of 1235 °C, partial melting takes place which results in carbide particle to penetrate through edge of the grains. During tempering at 530–600 °C, the retained austenite starts decomposing into martensite; although little amount of austenite still remains after tempering. There are two types of particles that can be seen in the OM image of HT-O1 tool steel which are massive white particle and small black particles. The black particles were recognized by XRD analysis as tempered martensite. XRD pattern of TiN shows that diffraction peaks at 37.5°, 43.5° and 62.8° corresponds to the (111), (200) and (220) orientation planes as shown in Fig. 1(c), it also confirms that TiN has FCC structure. Similar trend in XRD pattern was reported by L. Shan et al. [19] and N. W. khun et al. [20]. Average crystalline size of HT-O1 and TiN coated O1 tool
Please cite this article as: S. Kumar, S. R. Maity and L. Patnaik, Effect of heat treatment and TiN coating on AISI O1 cold work tool steel, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.367
S. Kumar et al. / Materials Today: Proceedings xxx (xxxx) xxx
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Fig. 1. OM image of (a) As-O1 tool steel (b) HT-O1 tool steel and (c) XRD pattern of heat treated and TiN coated O1 tool steel.
steel was obtained from Eq. (1) was 5.4 lm and 0.05 lm respectively. K Fukaura et al. [21] and F.F. Xia et al. [22] have also observed similar range of the crystalline sizes.
3.2. Elemental composition analysis EDS analysis used to draw information of surface composition of HT-O1 and TiN coated O1 tool steel. Results of EDS analysis is shown in Fig. 2(a), it validates the presence of tempered austenite in the globular grain form. The remaining interspaces were filled by accelerated eutectic carbides along the grain boundaries and lamellar network. It is specified by the increased amount of tungsten (W), chromium (Cr) and vanadium (V) in eutectic area. According to Fig. 2(b), Ti exhibited peaks of higher intensity which clearly indicates that it has higher atomic and weight percentage in the deposited coating. It also indicates that Ti elements have fitted well within the deposited particles. Fig. 2(b) suggests that N elements have also shaped well within the deposited particles which validates that N element did not oxidize.
3.3. Nanoindentation on as-O1, HT-O1 and TiN coated O1 tool steel Nanoindentation was performed to obtain the mechanical properties of substrates such as hardness and elastic modulus. It can be seen from the load vs. displacement curve shown in Fig. 3 that asO1 tool steel has higher residual depth (hr) than the HT-O1 and TiN coated O1 tool steel. Higher residual depth indicates lower hardness of the substrate. The hardness was obtained using Eq. (2) for as-O1, HT-O1 and TiN coated O1 tool steel was 2.45 GPa, 4.8 GPa and 19.6 GPa respectively. Furthermore, Elastic modulus was calculated using Eq. (3), and the values were 87 GPa, 188 GPa and 289 GPa for as-O1, HT-O1 and TiN coated O1 stool steel respectively as shown in Fig. 3. In summary, hardness and elastic modulus of substrates increased by 308% and 53.7% respectively after TiN coating. 3.4. Nanoscratch on as-O1, Ht-O1 and TiN coated O1 tool steel Nanoscratch test was performed to draw the information about wear properties of the substrates. Scratch hardness and specific
Fig. 2. EDX spectrum of (a) HT-O1 tool steel and (b) TiN coated O1tool steel.
Fig. 3. (a) Load vs. displacement and (b) Hardness and elastic modulus of as-O1, HT-O1 and TiN coated O1 tool steel.
Please cite this article as: S. Kumar, S. R. Maity and L. Patnaik, Effect of heat treatment and TiN coating on AISI O1 cold work tool steel, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.367
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S. Kumar et al. / Materials Today: Proceedings xxx (xxxx) xxx
Fig. 4. SPM image of scratch for (a) As-O1 tool steel, (b) HT-O1 tool steel and (c) TiN coated O1 tool steel.
Table 3 Chemical composition of AISI O1 tool steel. Substrate
As-O1 tool steel
HT-O1 tool steel
TiN coated O1 tool steel
Scratch hardness (in GPa) Specific wear rate (m2N1)
3.5 3.4 1015
6.85 2.7 1013
27.34 1.8 1012
on the coated surface. The hardness of O1 tool steel was increased by 2 times and 8 times respectively whereas elastic modulus was improved by 2.2 times and 3.3 times after heat treatment and TiN coating respectively. Nanoscratch test depicts that the specific wear rate was decreased to one order and three order after heat treatment and TiN coating respectively. Declaration of Competing Interest
wear rate were calculated using Eq. (4) and Eq. (5) respectively. The results of the same are tabulated in Table 2. Scratch hardness of the substrates was found higher than the nanoindentation hardness, it indicates that higher frictional force and lower coefficient of friction exist during scratch test. The activity of nanoindentation hardness and scratch hardness are very different in nature. During nanoindentation, indenter tip penetrates into the substrate surface at a static load whereas during scratch test indenter penetrate the substrate surface and slide forward to plough the material from surface. During ploughing lateral force is obstructed by the frictional force, hence more force is required to plough the material due to which scratch hardness has higher value than nanoindentation hardness. The mode of coating failure during scratch test is different for different material. Peeled of material get attached to scratch track which indicates plastic deformation of as-O1 tool steel. But HT-O1 and TiN coated O1 tool steel exhibited small amount of peeled out material particles which indicates brittleness of the substrate. It might be due to increase in residual stresses at the surface of the substrate. Scanning probe microscopy (SPM) was employed to record the scratch image of the substrates as shown in Fig. 4, it clearly shows that the scratch track of as-O1 tool steel have wider and deeper scratch profile than HT-O1 and TiN coated O1 tool steel. It revealed that as-O1 tool steel have higher specific wear rate than the HT-O1 and TiN coated O1 tool steel which is validated by the calculation of specific wear rate as shown in Table 3. 4. Conclusions Microstructure of O1 tool steel was to be observed martensitic in structure after heat treatment. XRD revealed the presence of carbide particles in the form of tempered martensite with crystalline size of 5.4 mm. HT-O1 tool steel was coated with TiN ceramic coating to improve its mechanical and wear properties. Ti and N elements were fitted well within the deposited particle. EDS spectrum of TiN coating showed that the N element have not oxidized
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. References [1] P.K. Jena, K.S. Kumar, T.B. Bhat, Metals Mater. Process. 19 (1/4) (2007) 339. [2] A. Akhbarizadeh, A. Shafyei, M.A. Golozar, Mater. Des. 30 (8) (2009) 3259– 3264. [3] A. Enver, U. Yunker, C. Merıç, Tribol. Int. 36 (3) (2003) 155–161. [4] Xiao, Lisong, D. Yan, Jining He, L. Zhu, Y. Dong, J. Zhang, X. Li, Appl. Surf. Sci. 253 (18) (2007) 7535–7539. [5] Akira Kobayashi, Surf. Coat. Technol. 132 (2–3) (2000) 152–157. [6] T. Bacci, L. Bertamini, F. Ferrari, F.P. Galliano, E. Galvanetto, Mater. Sci. Eng. A 283 (1–2) (2000) 189–195. [7] C. Schönjahn, M. Bamford, L.A. Donohue, D.B. Lewis, S. Forder, W.-D. Münz, Surf. Coat. Technol. 125 (1–3) (2000) 66–70. [8] M. Stoiber, S. Perlot, C. Mitterer, M. Beschliesser, C. Lugmair, R. Kullmer, Surf. Coat. Technol. 177 (2004) 348–354. [9] D.S. Rickerby, P.J. Burnett, Surf. Coat. Technol. 33 (1987) 191–211. [10] Lang, Fengqun, Z. Yu, Surf. Coat. Technol. 145 (1–3) (2001) 80–87. [11] Feng, Wenran, D. Yan, J. He, G. Zhang, G. Chen, W. Gu, S. Yang, Appl. Surf. Sci. 243 (1–4) (2005) 204–213. [12] B.S. Yilbas, M.S.J. Hashmi, S.Z. Shuja, Surf. Coat. Technol. 140 (3) (2001) 244– 250. [13] N. Laidani, J. Perriere, D. Lincot, A. Gicquel, J. Amouroux, Appl. Surf. Sci. 36 (1– 4) (1989) 520–529. [14] ASM Handbook, Principles and Practices for Iron and Steel, Heat Treaters Guide, 1995. [15] W.C. Oliver, G.M. Pharr, J. Mater. Res. 7 (06) (1992) 1564–1583. [16] Amini, Kamran, A. Akhbarizadeh, S. Javadpour, Vacuum 86 (10) (2012) 1534– 1540. [17] D. Das, A.K. Dutta, V. Toppo, K.K. Ray, Mater. Manuf. Process. 22 (4) (2007) 474–480. [18] L. Bourithis, G.D. Papadimitriou, J. Sideris, Tribol. Int. 39 (6) (2006) 479–489. [19] Shan, Lei, Y. Wang, J. Li, He Li, X. Wu, J. Chen, Surf. Coat. Technol. 226 (2013) 40–50. [20] Khun, N. Win, E. Liu, A.W.Y. Tan, D.S. Kumar, B. Albert, D.M. Lal, Friction 3 (3) (2015) 234–242. [21] Fukaura, Kenzo, Y. Yokoyama, D. Yokoi, N. Tsujii, K. Ono, Metall. Mater. Trans. A 35 (4) (2004) 1289–1300. [22] F.F. Xia, C. Liu, F. Wang, M.H. Wu, J.D. Wang, H.L. Fu, J.X. Wang, J. Alloy. Compd. 490 (1–2) (2010) 431–435.
Please cite this article as: S. Kumar, S. R. Maity and L. Patnaik, Effect of heat treatment and TiN coating on AISI O1 cold work tool steel, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.367
Contents lists available at ScienceDirect
Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr
Effect of heat treatment and TiN coating on AISI O1 cold work tool steel Sunil Kumar ⇑, Saikat Ranjan Maity, Lokeswar Patnaik Department of Mechanical Engineering, National Institute of Technology Silchar, Assam 788010, India
a r t i c l e
i n f o
Article history: Received 20 December 2019 Accepted 27 December 2019 Available online xxxx Keywords: AISI O1 Tool Steel Heat Treatment TiN coating XRD EDS
a b s t r a c t The effect of heat treatment and TiN coating on AISI O1 cold work tool steel was investigated. Microstructural and phase analysis was done using optical microscope and X-Ray diffraction. The crystalline size of heat treated and TiN coating were observed to be 5.4 lm and 0.05 lm respectively. Elemental composition was examined using Energy-dispersive spectroscopy. Mechanical and wear properties of substrate was analyzed using Hystron TI 950 Triboindentater. TiN coated substrate exhibited higher hardness (19.6 GPa) and elastic modulus (289 GPa) than the heat treated substrate. Hardness and elastic modulus post TiN coating was increased by 308% and 53.7% respectively. Lower specific wear rate was observed for TiN coated substrate (1.8 10–12 m2N1) than heat treated substrate (2.7 10–15 m2N1). In summary, TiN coated substrate has higher mechanical and wear resistance compared to heat treated substrate. Ó 2020 Elsevier Ltd. All rights reserved. Selection and of the scientific committee of the 10th International Conference of Materials Processing and Characterization.
1. Introduction Tool steel needs high strength with good toughness to resist the penetration and exhibit better shock absorbing capacity. Heat treatment along with quenching and tempering is playing a vital role to achieve these combined properties [1]. Low percentage of austenite was retained after heat treatment which is known as retained austenite, it is soft in nature which causes reduction in product life. Retained austenite have to transform into martensitic structure to accommodate the tooling requirements. The new transformed martensite has needle like structure which is excessive brittle in nature and leads to dimensional instability and it is known as retained martensite. Therefore, controlled transformation (quenching) is required to avoid the formation of retained martensite to improve the wear resistance of tool steel [2]. Wear resistance can be improve using various surface treatment processes where microstructural and chemical composition of surface can be modified. This is achieved by transformation hardening which improves the surface as well as volumetric properties of tool steel [3]. Wear resistance of tool steel can be improved using ceramic coatings like TiN, TiAlN, AlCrN and TiCrN etc. Titanium nitride
(TiN) coating is widely used in tooling industries for its lower coefficient of friction and excellent resistance to wear and corrosion [4–6]. TiN coating is deposited by cathode arc deposition using physical vapour deposition or chemical vapour deposition technique, where coating thickness upto 10 mm can be achieved due to lower coefficient of friction. Literature suggests that resistance to corrosion decreases with increasing coating thickness [7–10]. Metallic or non-metallic matrix with dense composite and fine scattered ceramic phase can be achieved using reactive plasma spraying (RPS) technique which also improves the wear property [11]. Precipitation of titanium and nitrogen before solidification is necessary for the TiN coating to attain higher strength and resistance to wear [12–13]. In this work, microstructural, mechanical and wear properties of heat treated (HT) and TiN coated AISI O1 cold work tool steel was studied and compared with as-O1 tool steel. Microstructural analysis was done for all the substrate using optical microscope (OM) and X-Ray diffraction (XRD). Furthermore, energydispersive spectroscopy (EDS) was used to analyze the elemental composition of the substrates. Finally, Nanoindentation and nanoscratch test was performed to examine the mechanical and wear properties of the substrates.
⇑ Corresponding author. E-mail address: [email protected] (S. Kumar). https://doi.org/10.1016/j.matpr.2019.12.367 2214-7853/Ó 2020 Elsevier Ltd. All rights reserved. Selection and of the scientific committee of the 10th International Conference of Materials Processing and Characterization.
Please cite this article as: S. Kumar, S. R. Maity and L. Patnaik, Effect of heat treatment and TiN coating on AISI O1 cold work tool steel, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.367
2
S. Kumar et al. / Materials Today: Proceedings xxx (xxxx) xxx
2. Material and method 2.1. Material AISI O1 cold work tool steel of 30 mm diameter was used as base metal (substrate) for this study. Chemical composition of the steel is tabulated in Table 1. Substrate was machined to maintain the size of Ø30 mm and thickness 10 mm. Substrate were heat treated according to ASM standards of hardening [14].
indenter. Indentation hardness and elastic modulus was obtained using Oliver and Pharr method [15]. 6000 mN load was applied at a rate of 600 mN/s during loading. Peak load was kept hold for 2 s and then released at 600 mN/s load during unloading. Total twenty number of indentations were performed to record the average value. Hardness and elastic modulus was calculated using Eqs. (2) and (3) respectively.
Hs ¼
Pmax Aðhc Þ
ð2Þ
2.2. Thin film coating
Where hc is contact depth and A is contact area. Pmax is the maximum load applied during indentation.
The heat treated samples were coated with TiN coating at Orlikon Balzer Coating India Ltd, Chennai using cathode arc deposition. The coating parameters are tabulated in Table 2.
1 ð1 v 2 Þ ð1 v 2i Þ þ ¼ Er E Ei
2.3. Thin film characterization Optical microscope (Dewinter optical, Inc.) was used to analyses the microstructure of as-O1 and HT-O1 tool steel. Substrates were polished with sand paper grit of 100, 250, 400, 800, 1000 and 1400 to achieve 2 mm of surface roughness. Polishing was done using diamond paste (size of 3 mm) on a rotating disc polishing machine. Finally, the substrates were cleaned with alcohol and dried using a blower. Prior to microscopic analysis the samples were etched with nital (solution of ethanol and HNO3). Phase of the crystal was analyzed using X-Ray diffraction (PANalytical B.V.) with CuKa radiation at accelerated potential of 40 KV. The diffraction angle ranges from 20°-80° at a speed 0.08 °/min. Each substrate was analyzed over a scanning region of 20 20 mm2. The crystalline size of substrate was calculated using Scherer Eq. (1). Elemental composition of HT-O1 tool steel and TiN coating were analyzed by EDS (Zeiss Supra 55-VP FEGSEM, Germany).
18Kk L ¼ qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 p b xCOSh
ð1Þ
Where K is the fatigue factor of the grains, k represents the wavelength of CuKa, b represents diffraction peak width at half height, x represents FWHM and h represents Bragg angle.
ð3Þ
E and v is elastic modulus and Poisson’s ratio the sample respectively, Ei is elastic modulus of indenter (1141 GPa) and v i is Poisson’s ratio of indenter (0.07). Nanoscratch was conducted with fixed load of 6000 mN for 10 mm scratch length. Image of scratch track was recorded using scanning probe microscopy (SPM). Scratch hardness and specific wear rate were calculated using Eq. (4) and Eq. (5) respectively.
Hs ¼ 2:31
PN w2
ð4Þ
Where P N is the maximum normal force applied to the indenter during scratch and w is width of scratch track.
K¼
V PL
ð5Þ
Where K is specific wear rate of the scratch (m2N1), V is volume of scratch (m3) obtained using Eq. (6), P is normal load (N) and L is total sliding distance (m).
V¼
1 2 cos ð70:3Þd l 2
ð6Þ
d and l are the depth (nm) and length of scratch wear track (m) respectively. 3. Results and discussion 3.1. Microstructural and XRD analysis
2.4. Nanoindentation and nanoscratch characterizations Hystron Ti950 Tribometer was used to performed nanoindentation and scratch test with 100 nm tip radius of Berkovich shaped
Table 1 Chemical composition of AISI O1 tool steel. Elements
C
Mn
Cr
W
V
Weight %
0.95
1.10
0.60
0.60
0.10
Table 2 Coating parameter for TiN coating. Coating parameters
Conditions
Etching duration Nitrogen (N2) gas flow rate Argon gas flow rate Planetary rotating speed Cathode amperage hour (Ah) Coating temperature Chamber pressure Coating bias voltage range Deposition time
30 min 4.67 106 m3/s 0.8 106 m3/s 2 rpm 600 Ah <500 °C 6 10-9 bar 50 V–600 V 4h
Microstructural and phase analysis of as-O1, HT-O1 and TiN coated O1 tool steel was analyzed by using OM and XRD as shown in Fig. 1. Principal of this characterization was to impart the nature, morphology, distribution of carbide particles and amount of austenite retained in the crystal. Fig. 1(b) depicts that carbide particles are present in the form of tempered martensite after the heat treatment. XRD pattern of HT-O1 steel confirms the presence of tempered martensite. Similar observations can be found elsewhere [16–18]. The quantity of fine carbide decreases with increasing austenitizing temperature. In addition to this, at higher austenitizing temperature of 1235 °C, partial melting takes place which results in carbide particle to penetrate through edge of the grains. During tempering at 530–600 °C, the retained austenite starts decomposing into martensite; although little amount of austenite still remains after tempering. There are two types of particles that can be seen in the OM image of HT-O1 tool steel which are massive white particle and small black particles. The black particles were recognized by XRD analysis as tempered martensite. XRD pattern of TiN shows that diffraction peaks at 37.5°, 43.5° and 62.8° corresponds to the (111), (200) and (220) orientation planes as shown in Fig. 1(c), it also confirms that TiN has FCC structure. Similar trend in XRD pattern was reported by L. Shan et al. [19] and N. W. khun et al. [20]. Average crystalline size of HT-O1 and TiN coated O1 tool
Please cite this article as: S. Kumar, S. R. Maity and L. Patnaik, Effect of heat treatment and TiN coating on AISI O1 cold work tool steel, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.367
S. Kumar et al. / Materials Today: Proceedings xxx (xxxx) xxx
3
Fig. 1. OM image of (a) As-O1 tool steel (b) HT-O1 tool steel and (c) XRD pattern of heat treated and TiN coated O1 tool steel.
steel was obtained from Eq. (1) was 5.4 lm and 0.05 lm respectively. K Fukaura et al. [21] and F.F. Xia et al. [22] have also observed similar range of the crystalline sizes.
3.2. Elemental composition analysis EDS analysis used to draw information of surface composition of HT-O1 and TiN coated O1 tool steel. Results of EDS analysis is shown in Fig. 2(a), it validates the presence of tempered austenite in the globular grain form. The remaining interspaces were filled by accelerated eutectic carbides along the grain boundaries and lamellar network. It is specified by the increased amount of tungsten (W), chromium (Cr) and vanadium (V) in eutectic area. According to Fig. 2(b), Ti exhibited peaks of higher intensity which clearly indicates that it has higher atomic and weight percentage in the deposited coating. It also indicates that Ti elements have fitted well within the deposited particles. Fig. 2(b) suggests that N elements have also shaped well within the deposited particles which validates that N element did not oxidize.
3.3. Nanoindentation on as-O1, HT-O1 and TiN coated O1 tool steel Nanoindentation was performed to obtain the mechanical properties of substrates such as hardness and elastic modulus. It can be seen from the load vs. displacement curve shown in Fig. 3 that asO1 tool steel has higher residual depth (hr) than the HT-O1 and TiN coated O1 tool steel. Higher residual depth indicates lower hardness of the substrate. The hardness was obtained using Eq. (2) for as-O1, HT-O1 and TiN coated O1 tool steel was 2.45 GPa, 4.8 GPa and 19.6 GPa respectively. Furthermore, Elastic modulus was calculated using Eq. (3), and the values were 87 GPa, 188 GPa and 289 GPa for as-O1, HT-O1 and TiN coated O1 stool steel respectively as shown in Fig. 3. In summary, hardness and elastic modulus of substrates increased by 308% and 53.7% respectively after TiN coating. 3.4. Nanoscratch on as-O1, Ht-O1 and TiN coated O1 tool steel Nanoscratch test was performed to draw the information about wear properties of the substrates. Scratch hardness and specific
Fig. 2. EDX spectrum of (a) HT-O1 tool steel and (b) TiN coated O1tool steel.
Fig. 3. (a) Load vs. displacement and (b) Hardness and elastic modulus of as-O1, HT-O1 and TiN coated O1 tool steel.
Please cite this article as: S. Kumar, S. R. Maity and L. Patnaik, Effect of heat treatment and TiN coating on AISI O1 cold work tool steel, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.367
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S. Kumar et al. / Materials Today: Proceedings xxx (xxxx) xxx
Fig. 4. SPM image of scratch for (a) As-O1 tool steel, (b) HT-O1 tool steel and (c) TiN coated O1 tool steel.
Table 3 Chemical composition of AISI O1 tool steel. Substrate
As-O1 tool steel
HT-O1 tool steel
TiN coated O1 tool steel
Scratch hardness (in GPa) Specific wear rate (m2N1)
3.5 3.4 1015
6.85 2.7 1013
27.34 1.8 1012
on the coated surface. The hardness of O1 tool steel was increased by 2 times and 8 times respectively whereas elastic modulus was improved by 2.2 times and 3.3 times after heat treatment and TiN coating respectively. Nanoscratch test depicts that the specific wear rate was decreased to one order and three order after heat treatment and TiN coating respectively. Declaration of Competing Interest
wear rate were calculated using Eq. (4) and Eq. (5) respectively. The results of the same are tabulated in Table 2. Scratch hardness of the substrates was found higher than the nanoindentation hardness, it indicates that higher frictional force and lower coefficient of friction exist during scratch test. The activity of nanoindentation hardness and scratch hardness are very different in nature. During nanoindentation, indenter tip penetrates into the substrate surface at a static load whereas during scratch test indenter penetrate the substrate surface and slide forward to plough the material from surface. During ploughing lateral force is obstructed by the frictional force, hence more force is required to plough the material due to which scratch hardness has higher value than nanoindentation hardness. The mode of coating failure during scratch test is different for different material. Peeled of material get attached to scratch track which indicates plastic deformation of as-O1 tool steel. But HT-O1 and TiN coated O1 tool steel exhibited small amount of peeled out material particles which indicates brittleness of the substrate. It might be due to increase in residual stresses at the surface of the substrate. Scanning probe microscopy (SPM) was employed to record the scratch image of the substrates as shown in Fig. 4, it clearly shows that the scratch track of as-O1 tool steel have wider and deeper scratch profile than HT-O1 and TiN coated O1 tool steel. It revealed that as-O1 tool steel have higher specific wear rate than the HT-O1 and TiN coated O1 tool steel which is validated by the calculation of specific wear rate as shown in Table 3. 4. Conclusions Microstructure of O1 tool steel was to be observed martensitic in structure after heat treatment. XRD revealed the presence of carbide particles in the form of tempered martensite with crystalline size of 5.4 mm. HT-O1 tool steel was coated with TiN ceramic coating to improve its mechanical and wear properties. Ti and N elements were fitted well within the deposited particle. EDS spectrum of TiN coating showed that the N element have not oxidized
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. References [1] P.K. Jena, K.S. Kumar, T.B. Bhat, Metals Mater. Process. 19 (1/4) (2007) 339. [2] A. Akhbarizadeh, A. Shafyei, M.A. Golozar, Mater. Des. 30 (8) (2009) 3259– 3264. [3] A. Enver, U. Yunker, C. Merıç, Tribol. Int. 36 (3) (2003) 155–161. [4] Xiao, Lisong, D. Yan, Jining He, L. Zhu, Y. Dong, J. Zhang, X. Li, Appl. Surf. Sci. 253 (18) (2007) 7535–7539. [5] Akira Kobayashi, Surf. Coat. Technol. 132 (2–3) (2000) 152–157. [6] T. Bacci, L. Bertamini, F. Ferrari, F.P. Galliano, E. Galvanetto, Mater. Sci. Eng. A 283 (1–2) (2000) 189–195. [7] C. Schönjahn, M. Bamford, L.A. Donohue, D.B. Lewis, S. Forder, W.-D. Münz, Surf. Coat. Technol. 125 (1–3) (2000) 66–70. [8] M. Stoiber, S. Perlot, C. Mitterer, M. Beschliesser, C. Lugmair, R. Kullmer, Surf. Coat. Technol. 177 (2004) 348–354. [9] D.S. Rickerby, P.J. Burnett, Surf. Coat. Technol. 33 (1987) 191–211. [10] Lang, Fengqun, Z. Yu, Surf. Coat. Technol. 145 (1–3) (2001) 80–87. [11] Feng, Wenran, D. Yan, J. He, G. Zhang, G. Chen, W. Gu, S. Yang, Appl. Surf. Sci. 243 (1–4) (2005) 204–213. [12] B.S. Yilbas, M.S.J. Hashmi, S.Z. Shuja, Surf. Coat. Technol. 140 (3) (2001) 244– 250. [13] N. Laidani, J. Perriere, D. Lincot, A. Gicquel, J. Amouroux, Appl. Surf. Sci. 36 (1– 4) (1989) 520–529. [14] ASM Handbook, Principles and Practices for Iron and Steel, Heat Treaters Guide, 1995. [15] W.C. Oliver, G.M. Pharr, J. Mater. Res. 7 (06) (1992) 1564–1583. [16] Amini, Kamran, A. Akhbarizadeh, S. Javadpour, Vacuum 86 (10) (2012) 1534– 1540. [17] D. Das, A.K. Dutta, V. Toppo, K.K. Ray, Mater. Manuf. Process. 22 (4) (2007) 474–480. [18] L. Bourithis, G.D. Papadimitriou, J. Sideris, Tribol. Int. 39 (6) (2006) 479–489. [19] Shan, Lei, Y. Wang, J. Li, He Li, X. Wu, J. Chen, Surf. Coat. Technol. 226 (2013) 40–50. [20] Khun, N. Win, E. Liu, A.W.Y. Tan, D.S. Kumar, B. Albert, D.M. Lal, Friction 3 (3) (2015) 234–242. [21] Fukaura, Kenzo, Y. Yokoyama, D. Yokoi, N. Tsujii, K. Ono, Metall. Mater. Trans. A 35 (4) (2004) 1289–1300. [22] F.F. Xia, C. Liu, F. Wang, M.H. Wu, J.D. Wang, H.L. Fu, J.X. Wang, J. Alloy. Compd. 490 (1–2) (2010) 431–435.
Please cite this article as: S. Kumar, S. R. Maity and L. Patnaik, Effect of heat treatment and TiN coating on AISI O1 cold work tool steel, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.367