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The effect of a boride diffusion layer on the tribological properties of AISI M2 steel
Wear 426–427 (2019) 1667–1671
Contents lists available at ScienceDirect
Wear journal homepage: www.elsevier.com/locate/wear
The effect of a boride diffusion layer on the tribological properties of AISI M2 steel
T
L. Gutierrez-Noda, C.A. Cuao-Moreu, O. Perez-Acosta, E. Lorenzo-Bonet, P. Zambrano-Robledo, ⁎ M.A.L. Hernandez-Rodriguez Universidad Autónoma de Nuevo León, FIME-CIDET, Av. Universidad S/N, 66455 San Nicolás de los Garza, Nuevo León, Mexico
ARTICLE INFO
ABSTRACT
Keywords: Boride coating Boriding Thermochemical surface hardening Cutting tools AISI M2 steel
AISI M2 high speed steel is commonly used as cutting tool in the machining process. Nevertheless, their useful life can be easily reduced by an eventual failure. In the last few years, thermochemical surface hardening process in which boron atoms diffuse into metals surface have been reported as an alternative to improve tribological properties. In the present work, a diffusional boron heat treatment was carried out at 950 °C by 6 h on AISI M2 steel sample. Scanning Electron Microscopy (SEM) and Micro-hardness testing was undertaken with the purpose to assess the diffusional boride microstructure and its effect on mechanical properties. On the other hand, tribological test was performed using a ball on disc tribometer tracking their friction coefficient and volume loss. Surface damage was analysed using stereomicroscopy and SEM. The boride diffusional layer achieved 50 µm with an increment of 7 times in the microhardness regarding to untreated sample and 4 times regarding to the adjacent zone to the boride layer. In addition, a reduction of the friction coefficient and better wear response was achieved as a result of boride heat treatment.
1. Introduction The machining process demands tools with the appropriate properties in order to guarantee high quality products. AISI M2 high speed steel is one of the most used materials in the fabrication of forming taps as a tool due to its good mechanical behavior. However, the reduction in the useful life of steel tools as a consequence of the excessive wear during the threading process has been one of the most critical issues [1–3]. In recent years, the improvement response on the tools surface in machining process, has become at a topic of interest, being the multilayer coatings obtained by physical vapor deposition (PVD) one of the most widely used [4,5]. Although, this technique improves wear resistance, it has been reported that coatings have adhesion problems [6]. On the other hand, boriding, which is a thermochemical surface hardening process in which boron atoms are diffused into the surface of a work-piece to form boride compounds with the base materials, could be a good alternative for improve the wear response [7–9]. In the case of tool steels, most authors have reported the effect of boride compounds in the surface mechanical properties. G. RodríguezCastro et al. [10] reported that the state of thermal residual stresses and the hardness of boride layers formed at the surface of an AISI D2 steel
⁎
were as function of the temperature and exposure time of the process. In other study, I. Ozbek et al. [11] examined the kinetics of boriding process on an AISI M2 high speed steel, measuring the range of diffusion and the formation of FeB and Fe2B compounds. Nevertheless, the wear performance of borided tool steels is a topic necessary to be studied in view of being considered as a useful and cheaper alternative in the improvement of hard steel tooling. The aim of this study was to analyze the improvement of the wear resistance of borided AISI M2 substrate obtained by a diffusional heat treatment. Wear response and metallurgical characterization of boride diffusional layers were determined by means of scanning electron microscopy (SEM) on cross-sections, micro-hardness testing, and ball-ondisc transitory analysis wear test under dry-sliding conditions was performed. 2. Materials and methods 2.1. Preparation of the samples The chemical composition of AISI M2 steel used in this study is given in Table 1. Discs with a diameter of 19 mm and a thickness of 8 mm were ground until P1200 grit SiC sandpaper and polished until
Corresponding author. E-mail address: [email protected] (M.A.L. Hernandez-Rodriguez).
https://doi.org/10.1016/j.wear.2019.01.089 Received 2 September 2018; Received in revised form 23 January 2019; Accepted 25 January 2019 0043-1648/ © 2019 Elsevier B.V. All rights reserved.
Wear 426–427 (2019) 1667–1671
L. Gutierrez-Noda et al.
Table 1 Chemical composition of AISI M2 high speed steel (wt%). Steel
C
Cr
W
Mo
V
Si
S
P
Mn
Fe
AISI M2
0.91
4.12
6.12
5
1.97
0.32
0.30 max
0.30 max
0.27
Bal.
the samples were carried out in a JEOL JSM-6510LV apparatus operated in backscattering mode and the thickness of the boride layers was determined. The hardness of the samples was measured by means of the Vickers indentation test. A HMV-2 Shimadzu Micro Hardness Tester was used. The hardness-depth profiles were obtained across the boride layers with an applied load of 490 mN for 15 s. Samples were prepared by conventional metallographic and etching using a solution of 5 mL HNO3, 200 mL HCl and 65 g FeCl3 [12]. 2.4. Tribological tests Friction and wear tests were carried out using a tribometer with a ball-on-disc configuration. Fig. 1 shows the different components of the STT-1 test rig used in this experiment. An alumina ball of a diameter of 11 mm was used at the following parameters: load of 40 N, sliding speed of 200 rpm, radius of circular wear track 3,75 mm and a total sliding distance of 282 m. The Hertzian contact pressure for the borided sample was 2.5 GPa, and 1.7 GPa for the untreated sample. The coefficient of friction as well as the progress of wear tracks were continuously recorded during each test. The volumetric wear was estimated according to the ASTM G99 – 06 standard [13]. After tribological test all conditions were analysed by SEM. Archard's equation was used to estimate the wear rate [14]:
Fig. 1. Ball-on-disc wear test machine STT-1.
mirror-like smoothness. 2.2. The boriding process Samples were placed inside a steel rectangular case containing B4C fresh powder mixture. The case was covered and sealed with SiO2 gel paint and placed in a preheated furnace at 950 °C during 6 h. Once the diffusional heat treatment was completed, the case was removed from the furnace and cooled at air until room temperature.
SN =
2.3. Morphological and mechanical characterization
V k
Where S is the wear relative distance (sliding distance), N is the applied load; k is a proportionality constant known as wear coefficient (or wear rate), and V is the volume loss (wear volume).
Scanning Electron Microscopy observations of the cross-sections of
Fig. 2. Cross-sectional SEM micrograph of the samples: (a) untreated, and borided at: (b) 350×, (c) 700×. 1668
Wear 426–427 (2019) 1667–1671
L. Gutierrez-Noda et al. 8
5,79
-5
3
Wear rate, 10 [mm /m.N]
6
4
2,06
2
0
Untreated
Borided
Fig. 5. Wear rate calculated at the surface of the borided and untreated AISI M2 steel disc samples tested in a ball-on-disc tribotester.
Fig. 3. Hardness depth profiles obtained with Vickers indentations on the borided surface of the AISI M2 steel.
0.6
a Untreated Borided
0.5
Coefficient of Friction
0.7
0.5
3
Volume loss [mm ]
0.6
0.4
0.4
0.3
b
0.2
0.3
0.1
0.2
0.0
0.1
0
50
100
150
200
250
Sliding distance [m]
0.0 0
50
100
150
200
250
Fig. 6. Variation of the friction coefficient obtained at the surface of AISI M2 steel disc samples. (a) Untreated, and (b) Borided.
300
Sliding distance [m] Fig. 4. Mean volumetric wear obtained at the surface of the borided and untreated AISI M2 steel disc samples tested against alumina balls in a ball-on-disc tribotester.
concentration gradient related with the diffusional process applied. Next to the diffusion zone (60 µm) the hardness of the substrate was around 6.5 GPa, being 4 times less regarding to the borided surface. Additionally, at a distance of (80 – 100 µm) from the borided surface and in the untreated sample the hardness was around 3.5 GPa. Thus, it can be appreciated that a hardening phenomenon was exhibited by the adjacent region to the diffusion zone.
3. Results and discussion 3.1. Morphological and mechanical characterization
3.2. Tribological results
Cross-sectional SEM image of the untreated sample is shown on Fig. 2a. For the borided surface SEM images are shown at Fig. 2b and c. According to Fig. 2c a diffusion layer with a thickness of 52 µm was obtained on the AISI M2 steel surface. Additionally, a uniform distribution of the boride layer can be observed, as well as a diffusion zone that separates the substrate from the borided surface (Fig. 2b). According to micro hardness results, a maximum hardness value of 25 GPa was achieved nearest the borided surface (Fig. 3). A lineal decreasement at hardness from the surface to the diffusion zone can be appreciated, which may be related to the boride compounds
The tribological behavior of the borided and untreated samples is shown in Figs. 4 and 5. According to the volume loss, the untreated sample had a pronounced slope during the running in, meanwhile the borided sample exhibited a stable volume loss. These results were consistent with the wear rates, in which boriding leaded to a better performance of the AISI M2 surface. In the case of coefficient of friction, the results are shown in Fig. 6. It could be seen that the lowest values were presented by the borided sample in a range of 0.3–0.4. Thus, the boriding treatment also reduced 1669
Wear 426–427 (2019) 1667–1671
L. Gutierrez-Noda et al.
Fig. 7. Images at a magnification of 4X obtained by stereoscope of transitory surface damage at different sliding distances of borided and untreated AISI M2 steel disc samples.
Fig. 8. Images at a magnification of 4X obtained by stereoscope of the surface damage presented by the alumina ball against the AISI M2 steel disc samples: (a) untreated and (b) borided.
the friction between the AISI M2 surface and the alumina ball, which is in agreement with E.A. dos S. de Almeida et al. [15], who also observed a reduction in friction coefficient due to boriding. On the other hand, it was possible to observe that at the untreated sample showed a drop on friction coefficient at about 150 m and at the same time an increasement on wear volume loss as is shown on Fig. 4. This increment on wear could be related with an increment in wear not only of the disc even so of the ceramic ball. Images at a magnification of 4X obtained by stereoscope at different sliding distances ae shown in Fig. 7. It can be seen that despite the borided sample presented a lower wear rate, the integrity of their wear track did not exhibited significant differences in comparison with the wear track of the untreated sample. In addition, for the untreated sample it was observed a higher amount of debris which could be related with the higher friction coefficient. Apparently it is possible to observe abrasion wear mechanisms with higher deformation regarding to the borided sample. Stereoscope images of the alumina balls used in the tests are shown in Fig. 8a and b. It can be appreciated that the alumina ball corresponding to the borided surface showed a contact plane of a larger diameter (600 µm) than the contact plane of the ball used in the untreated sample (400 µm). It could be explained due to that borided sample wore even more to the ceramic ball regarding to the untreated
sample. Fig. 9 shows the wear damaged surfaces for both conditions after the tribological tests. In Fig. 9a and b are presented the untreated condition micrographs, it was observed abrasion grooves along the sliding direction. In the case of borided sample, there was detachment of materials in certain areas as it can be shown at Fig. 9c and d, the wear mechanism was different regarding with pure abrasion of the untreated sample. In borided sample, crack formation and propagation resulted finally in a delamination wear mechanism. 4. Conclusions According to this study, the conclusions can be summarized as follows:
• Uniform distribution of boride layers with a significant thickness • • 1670
can be obtained on the surface of the AISI M2 steel by means of a heat treatment at 950 °C during 6 h. The boride layers obtained on the AISI M2 steel at 950 °C – 6 h allow to attain a gradual decrease of the hardness from the surface to the inner substrate. According to the tribological results, the wear rate of the borided AISI M2 steel is less than that of untreated steel due to the good
Wear 426–427 (2019) 1667–1671
L. Gutierrez-Noda et al.
Fig. 9. SEM micrographs of the wear tracks on M2 steel: (a), (b) untreated, and: (c), (d) borided.
mechanical performance of the boron compounds formed on the surface.
[6]
Acknowledgments
[7]
The authors wish to thank to “Concejo Nacional de Ciencia y Tecnología, (CONACYT) Mexico, CB-239808” for providing a master research fellowship, and express his grateful to CIDET (FIME) and CIIIA for allowing to perform each test.
[8] [9] [10]
References
[11] [12]
[1] J.F. Landeta, et al., Wear of form taps in threading of steel cold forged parts, J. Manuf. Sci. Eng. 137 (3) (2015) 031002. [2] P.R. Da Mota, et al., Performance of high-speed steel taps at high cutting speed, Int. J. Mach. Mach. Mater. 2 (2) (2007) 299–308. [3] S. Hogmark, M. Olsson, Wear mechanisms of HSS cutting tools, SME (Soc. Manuf. Eng.) Tech. Pap. (2005) 1–14. [4] D.-Y. Wang, Y.-W. Li, W.-Y. Ho, Deposition of high quality (Ti, Al) N hard coatings by vacuum arc evaporation process, Surf. Coat. Technol. 114 (2–3) (1999) 109–113. [5] M. Hua, et al., Tribological behaviours of patterned PVD TiN spot coatings on M2
[13] [14] [15]
1671
steel coated with different bias voltages, Surf. Coat. Technol. 200 (11) (2006) 3612–3625. H.A. Ching, et al., Effects of surface coating on reducing friction and wear of orthopaedic implants, Sci. Technol. Adv. Mater. 15 (1) (2014) 014402. Y. Kayali, İ. Güneş, S. Ulu, Diffusion kinetics of borided AISI 52100 and AISI 440C steels, Vacuum 86 (10) (2012) 1428–1434. S. Sen, et al., Mechanical behavior of borides formed on borided cold work tool steel, Surf. Coat. Technol. 135 (2–3) (2001) 173–177. A. Üçisik, C. Bindal, Fracture toughness of boride formed on low-alloy steels, Surf. Coat. Technol. 94 (1997) 561–565. G. Rodríguez-Castro, et al., Mechanical properties of FeB and Fe2B layers estimated by Berkovich nanoindentation on tool borided steel, Surf. Coat. Technol. 215 (2013) 291–299. I. Ozbek, C. Bindal, Kinetics of borided AISI M2 high speed steel, Vacuum 86 (4) (2011) 391–397. A.H. Vol, 9: metallography and Microstructures, ASM International, Materials Park, OH, 2004. A. Standard, G99, Standard test method for wear testing with a pin-on-disk apparatus, ASTM International, West Conshohocken, PA, 2006. K. Rutherford, I. Hutchings, Theory and application of a micro-scale abrasive wear test, J. Test. Eval. 25 (2) (1997) 250–260. Ed.S. de Almeida, et al., Sliding wear OF borided sintered AISI M2 steel coated WITH AlTiN/CrN multilayer, Wear (2018).
Contents lists available at ScienceDirect
Wear journal homepage: www.elsevier.com/locate/wear
The effect of a boride diffusion layer on the tribological properties of AISI M2 steel
T
L. Gutierrez-Noda, C.A. Cuao-Moreu, O. Perez-Acosta, E. Lorenzo-Bonet, P. Zambrano-Robledo, ⁎ M.A.L. Hernandez-Rodriguez Universidad Autónoma de Nuevo León, FIME-CIDET, Av. Universidad S/N, 66455 San Nicolás de los Garza, Nuevo León, Mexico
ARTICLE INFO
ABSTRACT
Keywords: Boride coating Boriding Thermochemical surface hardening Cutting tools AISI M2 steel
AISI M2 high speed steel is commonly used as cutting tool in the machining process. Nevertheless, their useful life can be easily reduced by an eventual failure. In the last few years, thermochemical surface hardening process in which boron atoms diffuse into metals surface have been reported as an alternative to improve tribological properties. In the present work, a diffusional boron heat treatment was carried out at 950 °C by 6 h on AISI M2 steel sample. Scanning Electron Microscopy (SEM) and Micro-hardness testing was undertaken with the purpose to assess the diffusional boride microstructure and its effect on mechanical properties. On the other hand, tribological test was performed using a ball on disc tribometer tracking their friction coefficient and volume loss. Surface damage was analysed using stereomicroscopy and SEM. The boride diffusional layer achieved 50 µm with an increment of 7 times in the microhardness regarding to untreated sample and 4 times regarding to the adjacent zone to the boride layer. In addition, a reduction of the friction coefficient and better wear response was achieved as a result of boride heat treatment.
1. Introduction The machining process demands tools with the appropriate properties in order to guarantee high quality products. AISI M2 high speed steel is one of the most used materials in the fabrication of forming taps as a tool due to its good mechanical behavior. However, the reduction in the useful life of steel tools as a consequence of the excessive wear during the threading process has been one of the most critical issues [1–3]. In recent years, the improvement response on the tools surface in machining process, has become at a topic of interest, being the multilayer coatings obtained by physical vapor deposition (PVD) one of the most widely used [4,5]. Although, this technique improves wear resistance, it has been reported that coatings have adhesion problems [6]. On the other hand, boriding, which is a thermochemical surface hardening process in which boron atoms are diffused into the surface of a work-piece to form boride compounds with the base materials, could be a good alternative for improve the wear response [7–9]. In the case of tool steels, most authors have reported the effect of boride compounds in the surface mechanical properties. G. RodríguezCastro et al. [10] reported that the state of thermal residual stresses and the hardness of boride layers formed at the surface of an AISI D2 steel
⁎
were as function of the temperature and exposure time of the process. In other study, I. Ozbek et al. [11] examined the kinetics of boriding process on an AISI M2 high speed steel, measuring the range of diffusion and the formation of FeB and Fe2B compounds. Nevertheless, the wear performance of borided tool steels is a topic necessary to be studied in view of being considered as a useful and cheaper alternative in the improvement of hard steel tooling. The aim of this study was to analyze the improvement of the wear resistance of borided AISI M2 substrate obtained by a diffusional heat treatment. Wear response and metallurgical characterization of boride diffusional layers were determined by means of scanning electron microscopy (SEM) on cross-sections, micro-hardness testing, and ball-ondisc transitory analysis wear test under dry-sliding conditions was performed. 2. Materials and methods 2.1. Preparation of the samples The chemical composition of AISI M2 steel used in this study is given in Table 1. Discs with a diameter of 19 mm and a thickness of 8 mm were ground until P1200 grit SiC sandpaper and polished until
Corresponding author. E-mail address: [email protected] (M.A.L. Hernandez-Rodriguez).
https://doi.org/10.1016/j.wear.2019.01.089 Received 2 September 2018; Received in revised form 23 January 2019; Accepted 25 January 2019 0043-1648/ © 2019 Elsevier B.V. All rights reserved.
Wear 426–427 (2019) 1667–1671
L. Gutierrez-Noda et al.
Table 1 Chemical composition of AISI M2 high speed steel (wt%). Steel
C
Cr
W
Mo
V
Si
S
P
Mn
Fe
AISI M2
0.91
4.12
6.12
5
1.97
0.32
0.30 max
0.30 max
0.27
Bal.
the samples were carried out in a JEOL JSM-6510LV apparatus operated in backscattering mode and the thickness of the boride layers was determined. The hardness of the samples was measured by means of the Vickers indentation test. A HMV-2 Shimadzu Micro Hardness Tester was used. The hardness-depth profiles were obtained across the boride layers with an applied load of 490 mN for 15 s. Samples were prepared by conventional metallographic and etching using a solution of 5 mL HNO3, 200 mL HCl and 65 g FeCl3 [12]. 2.4. Tribological tests Friction and wear tests were carried out using a tribometer with a ball-on-disc configuration. Fig. 1 shows the different components of the STT-1 test rig used in this experiment. An alumina ball of a diameter of 11 mm was used at the following parameters: load of 40 N, sliding speed of 200 rpm, radius of circular wear track 3,75 mm and a total sliding distance of 282 m. The Hertzian contact pressure for the borided sample was 2.5 GPa, and 1.7 GPa for the untreated sample. The coefficient of friction as well as the progress of wear tracks were continuously recorded during each test. The volumetric wear was estimated according to the ASTM G99 – 06 standard [13]. After tribological test all conditions were analysed by SEM. Archard's equation was used to estimate the wear rate [14]:
Fig. 1. Ball-on-disc wear test machine STT-1.
mirror-like smoothness. 2.2. The boriding process Samples were placed inside a steel rectangular case containing B4C fresh powder mixture. The case was covered and sealed with SiO2 gel paint and placed in a preheated furnace at 950 °C during 6 h. Once the diffusional heat treatment was completed, the case was removed from the furnace and cooled at air until room temperature.
SN =
2.3. Morphological and mechanical characterization
V k
Where S is the wear relative distance (sliding distance), N is the applied load; k is a proportionality constant known as wear coefficient (or wear rate), and V is the volume loss (wear volume).
Scanning Electron Microscopy observations of the cross-sections of
Fig. 2. Cross-sectional SEM micrograph of the samples: (a) untreated, and borided at: (b) 350×, (c) 700×. 1668
Wear 426–427 (2019) 1667–1671
L. Gutierrez-Noda et al. 8
5,79
-5
3
Wear rate, 10 [mm /m.N]
6
4
2,06
2
0
Untreated
Borided
Fig. 5. Wear rate calculated at the surface of the borided and untreated AISI M2 steel disc samples tested in a ball-on-disc tribotester.
Fig. 3. Hardness depth profiles obtained with Vickers indentations on the borided surface of the AISI M2 steel.
0.6
a Untreated Borided
0.5
Coefficient of Friction
0.7
0.5
3
Volume loss [mm ]
0.6
0.4
0.4
0.3
b
0.2
0.3
0.1
0.2
0.0
0.1
0
50
100
150
200
250
Sliding distance [m]
0.0 0
50
100
150
200
250
Fig. 6. Variation of the friction coefficient obtained at the surface of AISI M2 steel disc samples. (a) Untreated, and (b) Borided.
300
Sliding distance [m] Fig. 4. Mean volumetric wear obtained at the surface of the borided and untreated AISI M2 steel disc samples tested against alumina balls in a ball-on-disc tribotester.
concentration gradient related with the diffusional process applied. Next to the diffusion zone (60 µm) the hardness of the substrate was around 6.5 GPa, being 4 times less regarding to the borided surface. Additionally, at a distance of (80 – 100 µm) from the borided surface and in the untreated sample the hardness was around 3.5 GPa. Thus, it can be appreciated that a hardening phenomenon was exhibited by the adjacent region to the diffusion zone.
3. Results and discussion 3.1. Morphological and mechanical characterization
3.2. Tribological results
Cross-sectional SEM image of the untreated sample is shown on Fig. 2a. For the borided surface SEM images are shown at Fig. 2b and c. According to Fig. 2c a diffusion layer with a thickness of 52 µm was obtained on the AISI M2 steel surface. Additionally, a uniform distribution of the boride layer can be observed, as well as a diffusion zone that separates the substrate from the borided surface (Fig. 2b). According to micro hardness results, a maximum hardness value of 25 GPa was achieved nearest the borided surface (Fig. 3). A lineal decreasement at hardness from the surface to the diffusion zone can be appreciated, which may be related to the boride compounds
The tribological behavior of the borided and untreated samples is shown in Figs. 4 and 5. According to the volume loss, the untreated sample had a pronounced slope during the running in, meanwhile the borided sample exhibited a stable volume loss. These results were consistent with the wear rates, in which boriding leaded to a better performance of the AISI M2 surface. In the case of coefficient of friction, the results are shown in Fig. 6. It could be seen that the lowest values were presented by the borided sample in a range of 0.3–0.4. Thus, the boriding treatment also reduced 1669
Wear 426–427 (2019) 1667–1671
L. Gutierrez-Noda et al.
Fig. 7. Images at a magnification of 4X obtained by stereoscope of transitory surface damage at different sliding distances of borided and untreated AISI M2 steel disc samples.
Fig. 8. Images at a magnification of 4X obtained by stereoscope of the surface damage presented by the alumina ball against the AISI M2 steel disc samples: (a) untreated and (b) borided.
the friction between the AISI M2 surface and the alumina ball, which is in agreement with E.A. dos S. de Almeida et al. [15], who also observed a reduction in friction coefficient due to boriding. On the other hand, it was possible to observe that at the untreated sample showed a drop on friction coefficient at about 150 m and at the same time an increasement on wear volume loss as is shown on Fig. 4. This increment on wear could be related with an increment in wear not only of the disc even so of the ceramic ball. Images at a magnification of 4X obtained by stereoscope at different sliding distances ae shown in Fig. 7. It can be seen that despite the borided sample presented a lower wear rate, the integrity of their wear track did not exhibited significant differences in comparison with the wear track of the untreated sample. In addition, for the untreated sample it was observed a higher amount of debris which could be related with the higher friction coefficient. Apparently it is possible to observe abrasion wear mechanisms with higher deformation regarding to the borided sample. Stereoscope images of the alumina balls used in the tests are shown in Fig. 8a and b. It can be appreciated that the alumina ball corresponding to the borided surface showed a contact plane of a larger diameter (600 µm) than the contact plane of the ball used in the untreated sample (400 µm). It could be explained due to that borided sample wore even more to the ceramic ball regarding to the untreated
sample. Fig. 9 shows the wear damaged surfaces for both conditions after the tribological tests. In Fig. 9a and b are presented the untreated condition micrographs, it was observed abrasion grooves along the sliding direction. In the case of borided sample, there was detachment of materials in certain areas as it can be shown at Fig. 9c and d, the wear mechanism was different regarding with pure abrasion of the untreated sample. In borided sample, crack formation and propagation resulted finally in a delamination wear mechanism. 4. Conclusions According to this study, the conclusions can be summarized as follows:
• Uniform distribution of boride layers with a significant thickness • • 1670
can be obtained on the surface of the AISI M2 steel by means of a heat treatment at 950 °C during 6 h. The boride layers obtained on the AISI M2 steel at 950 °C – 6 h allow to attain a gradual decrease of the hardness from the surface to the inner substrate. According to the tribological results, the wear rate of the borided AISI M2 steel is less than that of untreated steel due to the good
Wear 426–427 (2019) 1667–1671
L. Gutierrez-Noda et al.
Fig. 9. SEM micrographs of the wear tracks on M2 steel: (a), (b) untreated, and: (c), (d) borided.
mechanical performance of the boron compounds formed on the surface.
[6]
Acknowledgments
[7]
The authors wish to thank to “Concejo Nacional de Ciencia y Tecnología, (CONACYT) Mexico, CB-239808” for providing a master research fellowship, and express his grateful to CIDET (FIME) and CIIIA for allowing to perform each test.
[8] [9] [10]
References
[11] [12]
[1] J.F. Landeta, et al., Wear of form taps in threading of steel cold forged parts, J. Manuf. Sci. Eng. 137 (3) (2015) 031002. [2] P.R. Da Mota, et al., Performance of high-speed steel taps at high cutting speed, Int. J. Mach. Mach. Mater. 2 (2) (2007) 299–308. [3] S. Hogmark, M. Olsson, Wear mechanisms of HSS cutting tools, SME (Soc. Manuf. Eng.) Tech. Pap. (2005) 1–14. [4] D.-Y. Wang, Y.-W. Li, W.-Y. Ho, Deposition of high quality (Ti, Al) N hard coatings by vacuum arc evaporation process, Surf. Coat. Technol. 114 (2–3) (1999) 109–113. [5] M. Hua, et al., Tribological behaviours of patterned PVD TiN spot coatings on M2
[13] [14] [15]
1671
steel coated with different bias voltages, Surf. Coat. Technol. 200 (11) (2006) 3612–3625. H.A. Ching, et al., Effects of surface coating on reducing friction and wear of orthopaedic implants, Sci. Technol. Adv. Mater. 15 (1) (2014) 014402. Y. Kayali, İ. Güneş, S. Ulu, Diffusion kinetics of borided AISI 52100 and AISI 440C steels, Vacuum 86 (10) (2012) 1428–1434. S. Sen, et al., Mechanical behavior of borides formed on borided cold work tool steel, Surf. Coat. Technol. 135 (2–3) (2001) 173–177. A. Üçisik, C. Bindal, Fracture toughness of boride formed on low-alloy steels, Surf. Coat. Technol. 94 (1997) 561–565. G. Rodríguez-Castro, et al., Mechanical properties of FeB and Fe2B layers estimated by Berkovich nanoindentation on tool borided steel, Surf. Coat. Technol. 215 (2013) 291–299. I. Ozbek, C. Bindal, Kinetics of borided AISI M2 high speed steel, Vacuum 86 (4) (2011) 391–397. A.H. Vol, 9: metallography and Microstructures, ASM International, Materials Park, OH, 2004. A. Standard, G99, Standard test method for wear testing with a pin-on-disk apparatus, ASTM International, West Conshohocken, PA, 2006. K. Rutherford, I. Hutchings, Theory and application of a micro-scale abrasive wear test, J. Test. Eval. 25 (2) (1997) 250–260. Ed.S. de Almeida, et al., Sliding wear OF borided sintered AISI M2 steel coated WITH AlTiN/CrN multilayer, Wear (2018).