- Email: [email protected]
Influence of Shallow and Deep Cryogenic Treatment on Tribological Behavior of En 19 Steel
Available online at G.sciencedirect.com *"#/
=JO
ScienceDirect
JOURNAL OF IRON AND STEEL RESEARCH, INTERNATIONAL. 2011 18(9): 53-59 9
Influence of Shallow and Deep Cryogenic Treatment on Tribological Behavior of En 19 Steel D Senthilkumar' ,
I Rajendran'
(Department of Mechanical Engineering, Dr Mahalingam College of Engineering and Technology, Pollachi 642 003, Tamil Nadu, India)
Abstract: The influence of cryogenic treatment on the wear resistance of En 19 steel was studied. Furthermore, a comparative analysis on the effect of Deep Cryogenic Treatment (DCT, -196 *C X 24 h) , Shallow Cryogenic Treatment (SCT, -80 *C X 5 h) and Conventional Heat Treatment ( C H T ) was done through dry sliding wear testing. The microstructures of C H T , SCT and DCT samples were also examined through scanning electron microscopy. The results indicated that the wear resistance of shallow and deep cryogenically treated samples is higher when compared to that of conventionally treated samples. X-ray diffraction pattern revealed that the transformation of retained austenite into martensite is responsible for the wear resistance improvement. Key words: steel; wear; cryogenic treatment; automotive
It has been observed quite a long time that the wear and corrosion are the most common problems in the heavy equipment of mineral processing industry owing to their significant impact on material loss and maintenance costs"]. For the past two decades, research efforts have been made with an aim to reduce the wear of mineral processing equipments (cyclones, pumps, and heavy medium vessels) and also to reduce the wear of automotive components ( crankshafts, connecting rods, axle, and gear ). Frequent replacement of these components increases the equipment downtime and maintenance cost, thereby reducing the process efficiencyCz1. One of the most prevalent claims in cryogenic treatment is an increase in wear resistance of certain ~ t e e l s [ ~ - ~ItI . is an affordable permanent treatment process that once affects the entire cross section of the steel componentC7].It promotes the transformation of the retained austenite into martensite at cryogenic temperatures and also facilitates the formation of fine carbides in the martensite, thereby improving the wear resistanceCB1. It has lots of benefits and gives dimensional stability to the material by improving wear resistance, strength and hardness of the materialsCg3.M Preciado et alC'O1pointed out that the deep cryogenic treatment (at - 190 ' C ) of quenched Biography: D Senthilkumar(l976-), Male, Master, Assistant Professor,
and tempered carburized steels would improve the wear resistance. This improvement is probably due to the segregation of carbon atoms and alloying elements during cryogenic cycle and the transformation of retained austenite into strain induced martensite. It is suggested that the carbides produced during this tempering could act as nuclei sites for posterior segregations during cryogenic treatment. However, scientific research on cryogenic treatment has been very few and only less number of research papers have been published on medium carbon steelsC"'. T h e alloy considered in the current study is En 19 chromium molybdenum steel. This material is significantly utilized in the fabrication of the components used in mineral processing industries. It also has a wide usage in the manufacture of automotive components such as crankshafts, axle shafts, connecting rods, gears, and propeller shafts joints, etc, where friction and wear are significant parameters. On this basis, development of tribological properties of En 1 9 steel is mandatory for the mineral processing and coal preparation industry, besides automotive industry. T h e main objective of this experimental study is to evaluate the influence of both Shallow Cryogenic Treatment (SCT, at -80 'C for 5 h) and Deep Cryogenic Treatment (DCT, at -196 "C for 24 h) E-mail: [email protected]; Received Date: August 16, 2010
54
on wear resistance of medium carbon steel En 1 9 , with respect to Conventional Heat Treatment ( CHT ). Microstructural analysis is also performed to explore the retained austenite contents of CHT, SCT and DCT samples.
1
Experimental
The chemical composition of the alloy En 19 chromium molybdenum steel is presented in Table 1. The experimental approach adopted in the present work is schematically shown in Fig. 1. Samples were subjected to C H T consisting of quench hardening in oil at 875 'C for 1 h. Part of samples was then subjected to Table 1
~1
SCT and DCT as indicated in A I3ensely et alc1''. By SCT, the conventionally quench-hardened samples were directly placed in a freezer, kept at -80 "C and held for 5 h to achieve thermal equilibrium. Samples were then extracted and cooled to room temperature in air. By DCT, the conventionally quench-hardened samples were gradually brought down from room temperature to - 196 "C at 1. 26 K/min and soaked at - 196 'C for 24 h , and then, they were slowly heated to room temperature at 0. 64 K/min. Finally, all the samples were subjected to tempering or stress relieving process at 200 "C for 60 min in order to impart toughness. (mass percent, ,%)
Chemical composition of En 19 steel
Sample
C
Si
Mn
P
S
Cr
Mo
Raw material
0.45f0.010
0. 3 5 f 0 . 0 1 3
0. 7 5 f 0 . 012
0.017f0.003
0.019f0.007
1. 1 9 f 0 . 0 0 7
0. 2 1 f 0 . 0 1 8
Shallow
cryogenic treatment at
IHardening at 875 9: for 1 h I I
Deep cryogenic U T L I . l l l T I I L at L L treatment
w 1 Tempering at 200 9: for 1h
Fig. 1
1.1
Vol. 18
Journal of Iron and Steel Research, International
Flow chart for experimental procedure
Dry sliding wear test Sliding wear, which is defined as the wear due to hard particles or hard protuberance forced against and moving along a solid surface, is believed to be one of the main wear types in the mining operat i ~ n " ~and ] in the automotive sectors. T h e wear tests of the En 19 steels were carried out in (DUCOM T R 20LE) pin-on-disc wear testing machine as per ASTM G99-95a[I4] by volume loss method. T h e sample was in the form of pin with diameter of 10 mm and length of 30 mm. T h e pin sample required for the wear test was made of E n 19 steel and a wear disc (160 mm in diameter, 8 mm in thickness) was
made of En 31 steel with HRC hardness of 64. The average surface roughness value of the flat circular disc was 0. 26 pm. The pin sample was fixed vertically and the required .load was applied against the rotating disk. Sliding occurred between the stationary pin and the rotating disc. In this study, the experiments were categorized into two different groups. The experimental parameters are given below. 1) Wear test parameters at lower loads The selected factors for the experiments were normal loads of 10 N , 20 N and 30 N , sliding speed of 1. 57 m/s, disc rotational speed of 300 r/min and the test duration of 900 s. The amount of wear was found out by measuring appropriate linear dimensions of pin sample before and after wear test for all the samples. T h e wear test was repeated twice under each condition. T h e tangential frictional force and the linear wear were measured with an accuracy of 0. l f 2 % of measured frictional force in Newton and 0 . 1 f1% of measured wear in micron. Linear measurements of wear were converted to wear volume for all the samples. 2) Wear test parameters at higher loads T h e wear tests were also performed for three different higher loads of 60 N , 70 N and 80 N , three sliding velocities of 2. 8 m/s, 3. 2 m/s and 3. 6 m/s and three different treatment conditions namely C H T , SCT and DCT, as indicated in A Bensely et alC1']. Each sample was tested for period of 720 s before obtaining the mass loss. T h e amount of wear at these higher loads was found out by mass loss method. The amount of wear is determined by weighing the spec-
Influence of Shallow and Deep Cryogenic Treatment on Tribological Behavior of En 19 Steel
Issue 9
imen before and after the tests using a precision electronic weighing balance with an accuracy of 0.000 1 g. Since the mass loss is measured, it is converted t o volume loss using the density of the specimen. T h e data obtained from the wear tests were presented a s wear resistance of pin sample for different treatments namely C H T , SCT and DCT. T h e wear rate is varied with the applied load and also with the sliding speed. As per the method used by R F Barron for finding out wear r e ~ i s t a n c e " ~ ' ,the influence on the wear resistance under different conditions of normal load was found out. T h e wear resistance is a non-dimensional parameter. T h e following formula was used to calculate the wear re~istance"~'.
WR=(F
v)/(W, H,)
(1)
where, W , is the wear resistance; F is the normal load, N; 'u is the linear velocity, mm/s; W , is the wear rate of pin, mm3/s; and H , is the Vickers hardness, N/mm2. The Archard wear coefficient (k) was also calculated for all the samples. The reciprocal of wear resistance is calculated from Eqn. (11, which is equal t o the Archard wear coefficient. T h e results of the average Vickers hardness values are reported in Table 2. Table 3 Conditions CHT SCT DCT
CHT SCT DCT
CHT SCT
DCT
(N
mrn-*>
Type of treatment
Hardness value
CHT SCT DCT
5 835 6 208 6 835
Microstructural study using optical microscope
T h e microstructures of C H T , SCT and DCT samples were studied through scanning electron microscope ( S E M ) . T h e samples were polished on a series of emery papers of grit 80, 120, 200, 600, 800, 10 0 0 , and up t o 1 pm. T h e n , the samples were polished by using diamond paste and finally all the samples were etched with 2% of Nital.
Results and Discussion
2 2.1
Wear tests at lower loads
T h e linear wear, tangential frictional force, wear resistance, wear coefficient and coefficient of friction for C H T , S C T and DCT samples for the applied normal load of 1 0 N , 20N and 30 N are obtained and given in Table 3 , Table 4, and Table 5 , respectively.
Wear test results at load of 10 N Average frictional force/N
Coefficient of friction
14. 1 13. 9
14
1.4
0.001758
12. 1 ll.
11.75
1. 18
0.001 176
8. 8 9. 1
8. 95
0. 90
Average frictional force/N
Coefficient of friction
Specimen
Wear/
Average
Wear
Wear
Frictional
pm
wear/pm
resistance
coefficient
force/N
c1 C2
75 83
79
390.49
0.002 560
s1
52
55 47
51
568.53
D1 D2
33 27
30
849.74
Wear test results at load of 20 N
Specimen
Wear/
Average
Wear
Wear
Frictional
identification
pm
wear/pm
resistance
coefficient
force/N
c3 c4
155 167
161
383.21
0.002 609
15. 7 15. 9
15. 8
0. 79
s3
s4
108 104
106
547.07
0.001 828
13. 8 13. 7
13.75
0. 69
D3 D4
66 60
63
809.27
0.001 236
10. 5 10. 7
10. 6
0. 53
Specimen
Wear/
Average
Wear
Wear
Frictional
identification
pm
wear/pm
resistance
coefficient
force/N
Average frictional force/N
Coefficient of friction
c5
244 246
245
377.74
0.002 647
18. 2 17. 9
18.05
0. 60
S6
157 169
163
533.65
0.001 873
16. 7 16. 3
16. 5
0. 55
D5 D6
103 99
101
757.19
0.001 321
15. 5 15. 2
15.35
0. 51
Table 5 Conditions
1.2
Vickers hardness of En 19 steel
identification
Table 4 Conditions
Table 2
55 '
C6
s5
Wear test results at load of 30 N
56
Journal of Iron and Steel Research, International
In this study of frictional behavior, the steady state was attained after approximately 100 s and the coefficient of friction was found after the steady state. This value is continuous until the end of the test. T h e coefficient of friction is dependent on the sliding velocity t o some extent. T h e frictional force a t high velocity (1. 57 m / s > was the result of asperit y deformation and the corresponding high frictional energy dissipating a t the sliding interfaceCI6'. For load of 10 N , the coefficient of friction was found t o be 1. 40 for C H T samples, 1. 18 for S C T samples, and 0. 90 for DCT samples, respectively, a s indicated in Table 3. T h e coefficient of friction has a relatively high value for the low normal load of 10 N. However, Prasanta S a h ~ o " ~reported ' that the coefficient of friction in sliding wear varies between 0. 8 and 1. 5 for the unlubricated self-mated iron steel pairs. I t is obvious that the coefficient of friction of S C T and DCT samples was lower than that of CHT samples for a normal load of 10 N. This may be contributed t o the transformation of retained austenite t o martensite along with the carbide precipitations. T h e reduction of the coefficient of friction with supplementing the cryogenic treatment is expected t o be a result of increasing the hardness and particularly compressive residual stress on the surface of the steel. Previous X-ray diffractometry studies revealed that when compared to those of C H T samples ( + 108.1 MPa), the residual stresses on surface were found t o decrease by 164% for DCT samples (-69.1 MPa) and I t proved 8 2 % for S C T samples ( +19. 6 MPa)"']. that S C T and DCT help t o reduce the residual stress on the surface of the E n 19 steel. This leads t o an increase in hardness, wear resistance, fatigue and impact resistance of the steel components. I t also gives the resistance t o the crack growth. T h e wear resistance has been increased by 45.59% for SCT samples and 117. 6 1 % for DCT samples when compared t o C H T for a n applied load of 10 N. I t also proves that the wear resistance of DCT samples is 49.46% higher than that of S C T samples for an applied load of 10 N , a s evaluated from Table 3. For a n applied load of 20 N , the coefficient of friction is reduced from 0. 79 (for C H T samples) t o 0. 69 ( f o r S C T samples) and further t o 0. 53 ( f o r DCT samples), respectively, a s given in Table 4. And the wear resistance has been increased by 42.76% for S C T samples and 111.18% for DCT samples when compared t o C H T samples. Also the wear resistance of D C T samples is 47. 92% more than that of SCT samples.
Vol. 18
-
A t a load of 30 N , the coefficient of friction is reduced from 0. 60 (for CHT samples) t o 0. 55 (for S C T samples) and further t o 0. 51 ( f o r DCT samples), a s indicated in Table 5. T h e wear resistance has been increased by 41. 27% for SCT samples and 100.46% for DCT samples when compared t o C H T samples. T h e wear resistance of DCT samples is 41. 89% higher than that of SCT samples, a s indicated in Table 5. Hence, it proves that SCT and DCT have more potential t o enhance the wear resistance of E n 19 steels than C H T . T h e Archard wear coefficient for CHT, SCT and DCT samples for the applied normal load of 10 N , 20 N and 30 N are also shown in Table 3, Table 4 and Table 5 , respectively. With an increase in applied normal load for a given sliding velocity, the wear loss increases in all the three different types of samples. These observations indicate that they abide by Archard law. I t states that the amount of wear volume is proportional t o the applied normal load and sliding distance. It is also inversely proportional t o the hardness of the surface of the material. T h e Archard wear coefficient is dimensionless and it is always less than unity. T h e dimensionless wear coefficient is of paramount importance and it gives a valuable means of comparing the severity of wear process in different systems. When the steel round cylinders are quenched, surface is always cooled faster thanthe centre and undergoes martensitic transformation first, which hardens the surface relative t o the centre['']. After cryogenic treatment, retained austenite volume a t the surface is lower than that of sub-surface resulting from non-martensite anomaly layers. Austenite volume increases up t o a few microns from the surface anomaly layer. T h e change in the microstructure with distance along a diameter is accompanied by a corresponding variation in the wear resistance of the material. Therefore, the improvement in wear resistance of both SCT and DCT samples when compared t o C H T samples decreases with a n increase in normal load and also there is a reduction in coefficient of friction with the increase in normal load for each sample respectively.
2 . 2 Wear tests at higher loads 2. 2. 1 Enhancement in wear resistance w i t h vary i n g loads at constant speed T h e wear resistance of CHT, SCT and DCT samples for the applied normal load of 60 N , 70 N and 80 N is analyzed, and the results are tabulated in Table 6.
Influence of Shallow and Deep Cryogenic Treatment on Tribological Behavior of En 19 Steel
Issue 9
Table 6 I.oad/N
60
Sliding velocity/
Wear resistance
Wear coefficient
CHT
SCT
DCT
CHT
SCT
DCT
2. 8 3. 2
22 258
86693 79740 66778
4 . 4 9 3 ~10-5 4. 7 1 1 X 1 0 - 5 5. s o x 10-5
I. 7 0 2 x 10-5 1. 8 7 9 x 10-5
1. i 5 3 x 10-5
21229 18690
58738 53208 45116
I. 2 5 4 x 10-5
2. 2 1 7 X 1 0 - 5
1 . 4 9 7 ~10-5
48154 40970 33085
67428 58144 46745
5. 2 2 2 x 10-5
2. 0 7 7 x 10-5
3. 2 3. 6
19148 16765 14080
5 . 9 6 5 ~10-5
2.441
1 . 4 8 3 ~10-5 1. 7 z o x 10-5
iozx 10-5
x 10-5
3. 0 2 3 x 10-5
2. i 3 9 x 10-5
2. 8 3. 2 3. 6
16412. 13249 11494
39159 31216 26468
56 044 44300 36985
6.093 X 10K5 7 . 5 4 8 ~10-5
2 . 5 5 4 ~10-5 3. 2 0 3 x 10-5 3 . 7 7 8 ~10-5
2. 2 5 7 x 10-5
2. 8
80
Wear test results at higher loads
( m * s-')
3. 6 70
57
T h e wear resistance has been increased by 164% for SCT samples and 289% for DCT samples when compared to C H T samples with an applied normal load of 60 N at a sliding speed of 2.8 m/s. For an applied load of 70 N at sliding speed of 2.8 m/s, the wear resistance has been enhanced by 151% for SCT samples and 252% for DCT samples when compared to- C H T samples. At a load of 80 N , the wear resistance of SCT and DCT samples is 139% and 241% more than that of C H T , respectively. It proves that at higher normal loads, the improvements in wear resistance of SCT and DCT with respect to that C H T decreases with increasing load at a sliding speed of 2 .8 m/s. For a load of 60 N a t a sliding speed of 3. 2 m/s, the wear resistance of SCT and DCT samples was 151% and 276 % higher than that of C H T samples, respectively. For a load of 70 N , the wear resistance of SCT and DCT sample is 144% and 247% more than that of C H T samples, respectively. It is found that at a load of 80 N and a sliding speed of 3. 2 m/s, the wear resistance of SCT and DCT samples is 136% and 234% more than that of C H T samples, respectively. The improvement in wear resistance of SCT and DCT samples with respect t o that of C H T samples decreases when the load increases at a sliding speed of 3. 2 m/s. At a load of 60 N and a sliding speed of 3.6 m/s, the wear resistance has been increased by 141% for SCT samples and 257% for DCT samples with respect to C H T samples. The wear resistance of SCT and DCT samples is 135% and 232% for an applied load of 70 N , respectively. At a load of 80 N , the wear resistance of SCT and DCT samples is 130% and 222% more than that of CHT, respectively. The enhancement in wear resistance of SCT and DCT samples with respect to that of C H T samples decreases as the load increases.
7.
8.700X
1 . 7 8 4 ~10-5 2 . 7 0 4 ~10-5
The variations of wear coefficient in the samples of C H T , SCT and DCT for the applied normal load of 60 N , 70 N and 80 N at a sliding speed of 2.8 m/s, 3.2 m/s and 3. 6 m/s are also indicated in Table 6. With an increase in applied normal load for a given sliding speed, the wear loss increases in all the C H T , SCT and DCT samples. 2. 2. 2 Enhancement in wear resistance w i t h varying speed at constant load The wear resistance of all the C H T , SCT and DCT samples at different sliding speeds with a load of 60 N is also analyzed from Table 6. A t a load of 60 N , the wear resistance of SCT and DCT samples with respect to that of C H T samples decreases with an increase in the sliding speed. It proves that the development of wear resistance of all the SCT and DCT samples with a load of 70 N and 80 N decreases with the increase in sliding speed. Finally, the above study reveals that the enhancements in wear resistance of SCT and DCT samples compared to that of C H T samples decreases with an increase in load under the same condition of sliding speed and decreases with an increase in sliding speed under identical condition of load.
2.3
Microstructure analysis Previous studies report the retained austenite present in the samples of En 19 steel when subjected to C H T , SCT and DCT using X-ray diffraction techniques. After C H T of steel samples, there is 6. 5% of retained austenite. The sample after SCT results in the reduction of retained austenite from 6. 5% to 5. 1%. The sample after DCT results in a further reduction of retained austenite from 6. 5% ( C H T ) to 2.7%. The reduction of retained austenite content in the SCT and DCT samples shows that cryogenic treatment promotes the transformation of retained austenite into martensite. This causes an increase in
58
J o u r n a l of Iron a n d S t e e l R e s e a r c h , International
wear resistance of En 19 steels. The microstructural studies of the treated samples were carried out to see if any significant change occurred. Fig. 2 shows the SEM micrographs of C H T , SCT and DCT samples. There are no microstructural changes observed between CHT, SCT and DCT samples. That is, no
~~~~
Fig. 2
3
~
~~
Microstructure of CHT sample ( a ) , SCT sample (b) , and DCT sample (19
Conclusions
cryogenic treatment promote the transformation of retained austenite to martensite, thereby causing a significant increase in wear resistance. 2 ) Wear resistance has been increased by 118. 38% for SCT samples and 214.94% for DCT samples when compared to C H T samples. In addition, the increase in wear resistance of DCT samples is 44.39% with respect to SCT samples. 3 ) Wear is increased linearly with respect t o load at constant sliding velocity. T h e wear is also increased linearly with respect to sliding velocity at constant applied load. 4) T h e lowest coefficient of friction is obtained in DCT samples treated at -196 "C for 24 h. 5) T h e improvements in wear resistance of both SCT and DCT samples with respect to C H T samples decreases with increasing load and also there is a reduction in coefficient of friction with the increasing load for each sample.
T h e authors wish to thank Professor M Pellizzari o f Department o f Materials Engineering and Industrial Technologies, University o f Trento , I t a l y f o r having extended his rnetallurgical facilities f o r the successful completion o f work. References:
[S]
appreciable difference could be detected by SEM owing to small amount (less than 1 0 % ) of retained auspointed out that tenite"". However, J Y Huang et alCzo1 the precipitation of fine carbides and the transformation of retained austenite into martensite contribute to the improvement of wear resistance.
~~~~
1) Both deep cryogenic treatment and shallow
[I]
Vol. 18
Dunn D J. Metal Removal Mechanisms Comprising Wear in Mineral Processing [C] // Ludema K C. Proceedings of International Conference on Wear of Materials. New York: ASME International, 1985: 2417. T a o D, Blue C , Dahotre N B, et al. High-Density-Infrared (HDI) Treatment of Mineral Processing Equipment for En-
hanced Wear Resistance [J]. Minerals Engineering, 2006, 19 (2): 190. Leskovsek V, Kalin M, Vizintin J. Influence of Deep-Cryogenic Treatment on Wear Resistance of Vacuum Heat-Treated HSS [J]. Vacuum, 2006, 80(6): 507. Barron R F. Effect of Cryogenic Treatment on Lathe Tool Wear [J]. Progress in Refrigeration Science and Technology, 1973, 1: 529. LIU Hao-huai, WANG Jun, S H E N Bao-luo, et al. Effects of Deep Cryogenic Treatment on Property of 3Cr13MolVl. 5 High Chromium Cast Iron [J]. Materials and Design, 2007, 28 (3) : 1059. Yong A Y L , Seah K H W, Rahman M. Performance Evaluation of Cryogenically Treated Tungsten Carbide Tools in Turning [J]. International Journal of Machine Tools and Manufae ture, 2006, 46(15): 2051. Mohanlal D, Renganarayanan S, Kalanidhi A. Cryogenic Treatment to Augment Wear Resistance of Tool and Die Steels [J]. Cryogenics, 2001, 41(3): 149. Collins D N , Dormer J. Deep Cryogenic Treatment of a D2 Cold-Work Tool Steel [J]. Heat Treatment of Metals, 1997, 3: 71. Molinari M , Pellizzari M , Gialanella S, et al. Effect of Deep Cryogenic Treatment on the Mechanical Properties of Tool Steels [J]. Journal of Materials Processing Technology, 2001, 118(1/2/3): 350. Preciado M, Bravo P M, Alegre J M. Effect of Low Temperature Tempering Prior Cryogenic Treatment on Carburized Steels [J]. Journal of Materials Processing Technology, 2006, 176(1/2/3): 41. Zhirafar S, Rezaeian A , Pugh M. Effect of Cryogenic Treatment on the Mechanical Properties of 4340 Steel [J]. Journal of Materials Processing Technology, 2007, 186(1/2/3) : 298. Bensely A , Senthilkumar D, Mohanlal D, et al. Effect of C r y ogenic Treatment on Tensile Behavior of Case Carburized Steel-815M17 [J]. Materials Characterization, 2007. 58(5) : 485. Xu L , Vose C, S t John D. Abrasive Wear Study of Selected White Cast Irons a s Liner Materials for the Mining Industry [J]. Wear, 1993, 162-164(Part 2): 820. ASTM Standards. G99-05, Standard Test Methods for Wear Testing With a Pin on Disk Apparatus [S]. New York: ASM International, 2005.
Issue 9 [15]
[16]
[17]
Influence of Shallow and Deep Cryogenic Treatment on Tribological Behavior of En 19 Steel Barron RF. Do Treatments at Temperature Below -120 'F Help Increase the Wear Resistance of Tool Steels? Here are Some Research Findings That They Do [J]. Heat Treating, 1974, 5: 14. Li J , Sheng X H. Nan0 Tribology Characteristics of Ti02 Films on 3-Mercaptopropyl Trimethoxysilane .Sulfonated SelfAssembled Monolayer [J]. Bulletins of Material Science, 2009, 32(5): 481. Prasanta S. Engineering Tribology [MI. New Delhi: Prentice Hall of India, 2008.
[18]
[19]
[20]
' 59 '
Senthilkumar D, Rajendran I , Pellizzari M , et al. Influence of Shallow and Deep Cryogenic Treatment on the Residual State of Stress of 4140 Steel [J]. Journal of Materials Processing Technology, 2011, 211(3): 396. Robert E, Reed-Hill, Reza Abbaschian. Physical Metallurgy Principle [MI. 3rd ed. Singapore: Thomson Asia Pte Ltd, 2003. Huang J Y, Zhu Y T, Liao X Z, et al. Microstructure of Cryogenic Treated M2 Tool Steel [J]. Materials Science and Engineering, 2003, 339A(1/2): 241.
=JO
ScienceDirect
JOURNAL OF IRON AND STEEL RESEARCH, INTERNATIONAL. 2011 18(9): 53-59 9
Influence of Shallow and Deep Cryogenic Treatment on Tribological Behavior of En 19 Steel D Senthilkumar' ,
I Rajendran'
(Department of Mechanical Engineering, Dr Mahalingam College of Engineering and Technology, Pollachi 642 003, Tamil Nadu, India)
Abstract: The influence of cryogenic treatment on the wear resistance of En 19 steel was studied. Furthermore, a comparative analysis on the effect of Deep Cryogenic Treatment (DCT, -196 *C X 24 h) , Shallow Cryogenic Treatment (SCT, -80 *C X 5 h) and Conventional Heat Treatment ( C H T ) was done through dry sliding wear testing. The microstructures of C H T , SCT and DCT samples were also examined through scanning electron microscopy. The results indicated that the wear resistance of shallow and deep cryogenically treated samples is higher when compared to that of conventionally treated samples. X-ray diffraction pattern revealed that the transformation of retained austenite into martensite is responsible for the wear resistance improvement. Key words: steel; wear; cryogenic treatment; automotive
It has been observed quite a long time that the wear and corrosion are the most common problems in the heavy equipment of mineral processing industry owing to their significant impact on material loss and maintenance costs"]. For the past two decades, research efforts have been made with an aim to reduce the wear of mineral processing equipments (cyclones, pumps, and heavy medium vessels) and also to reduce the wear of automotive components ( crankshafts, connecting rods, axle, and gear ). Frequent replacement of these components increases the equipment downtime and maintenance cost, thereby reducing the process efficiencyCz1. One of the most prevalent claims in cryogenic treatment is an increase in wear resistance of certain ~ t e e l s [ ~ - ~ItI . is an affordable permanent treatment process that once affects the entire cross section of the steel componentC7].It promotes the transformation of the retained austenite into martensite at cryogenic temperatures and also facilitates the formation of fine carbides in the martensite, thereby improving the wear resistanceCB1. It has lots of benefits and gives dimensional stability to the material by improving wear resistance, strength and hardness of the materialsCg3.M Preciado et alC'O1pointed out that the deep cryogenic treatment (at - 190 ' C ) of quenched Biography: D Senthilkumar(l976-), Male, Master, Assistant Professor,
and tempered carburized steels would improve the wear resistance. This improvement is probably due to the segregation of carbon atoms and alloying elements during cryogenic cycle and the transformation of retained austenite into strain induced martensite. It is suggested that the carbides produced during this tempering could act as nuclei sites for posterior segregations during cryogenic treatment. However, scientific research on cryogenic treatment has been very few and only less number of research papers have been published on medium carbon steelsC"'. T h e alloy considered in the current study is En 19 chromium molybdenum steel. This material is significantly utilized in the fabrication of the components used in mineral processing industries. It also has a wide usage in the manufacture of automotive components such as crankshafts, axle shafts, connecting rods, gears, and propeller shafts joints, etc, where friction and wear are significant parameters. On this basis, development of tribological properties of En 1 9 steel is mandatory for the mineral processing and coal preparation industry, besides automotive industry. T h e main objective of this experimental study is to evaluate the influence of both Shallow Cryogenic Treatment (SCT, at -80 'C for 5 h) and Deep Cryogenic Treatment (DCT, at -196 "C for 24 h) E-mail: [email protected]; Received Date: August 16, 2010
54
on wear resistance of medium carbon steel En 1 9 , with respect to Conventional Heat Treatment ( CHT ). Microstructural analysis is also performed to explore the retained austenite contents of CHT, SCT and DCT samples.
1
Experimental
The chemical composition of the alloy En 19 chromium molybdenum steel is presented in Table 1. The experimental approach adopted in the present work is schematically shown in Fig. 1. Samples were subjected to C H T consisting of quench hardening in oil at 875 'C for 1 h. Part of samples was then subjected to Table 1
~1
SCT and DCT as indicated in A I3ensely et alc1''. By SCT, the conventionally quench-hardened samples were directly placed in a freezer, kept at -80 "C and held for 5 h to achieve thermal equilibrium. Samples were then extracted and cooled to room temperature in air. By DCT, the conventionally quench-hardened samples were gradually brought down from room temperature to - 196 "C at 1. 26 K/min and soaked at - 196 'C for 24 h , and then, they were slowly heated to room temperature at 0. 64 K/min. Finally, all the samples were subjected to tempering or stress relieving process at 200 "C for 60 min in order to impart toughness. (mass percent, ,%)
Chemical composition of En 19 steel
Sample
C
Si
Mn
P
S
Cr
Mo
Raw material
0.45f0.010
0. 3 5 f 0 . 0 1 3
0. 7 5 f 0 . 012
0.017f0.003
0.019f0.007
1. 1 9 f 0 . 0 0 7
0. 2 1 f 0 . 0 1 8
Shallow
cryogenic treatment at
IHardening at 875 9: for 1 h I I
Deep cryogenic U T L I . l l l T I I L at L L treatment
w 1 Tempering at 200 9: for 1h
Fig. 1
1.1
Vol. 18
Journal of Iron and Steel Research, International
Flow chart for experimental procedure
Dry sliding wear test Sliding wear, which is defined as the wear due to hard particles or hard protuberance forced against and moving along a solid surface, is believed to be one of the main wear types in the mining operat i ~ n " ~and ] in the automotive sectors. T h e wear tests of the En 19 steels were carried out in (DUCOM T R 20LE) pin-on-disc wear testing machine as per ASTM G99-95a[I4] by volume loss method. T h e sample was in the form of pin with diameter of 10 mm and length of 30 mm. T h e pin sample required for the wear test was made of E n 19 steel and a wear disc (160 mm in diameter, 8 mm in thickness) was
made of En 31 steel with HRC hardness of 64. The average surface roughness value of the flat circular disc was 0. 26 pm. The pin sample was fixed vertically and the required .load was applied against the rotating disk. Sliding occurred between the stationary pin and the rotating disc. In this study, the experiments were categorized into two different groups. The experimental parameters are given below. 1) Wear test parameters at lower loads The selected factors for the experiments were normal loads of 10 N , 20 N and 30 N , sliding speed of 1. 57 m/s, disc rotational speed of 300 r/min and the test duration of 900 s. The amount of wear was found out by measuring appropriate linear dimensions of pin sample before and after wear test for all the samples. T h e wear test was repeated twice under each condition. T h e tangential frictional force and the linear wear were measured with an accuracy of 0. l f 2 % of measured frictional force in Newton and 0 . 1 f1% of measured wear in micron. Linear measurements of wear were converted to wear volume for all the samples. 2) Wear test parameters at higher loads T h e wear tests were also performed for three different higher loads of 60 N , 70 N and 80 N , three sliding velocities of 2. 8 m/s, 3. 2 m/s and 3. 6 m/s and three different treatment conditions namely C H T , SCT and DCT, as indicated in A Bensely et alC1']. Each sample was tested for period of 720 s before obtaining the mass loss. T h e amount of wear at these higher loads was found out by mass loss method. The amount of wear is determined by weighing the spec-
Influence of Shallow and Deep Cryogenic Treatment on Tribological Behavior of En 19 Steel
Issue 9
imen before and after the tests using a precision electronic weighing balance with an accuracy of 0.000 1 g. Since the mass loss is measured, it is converted t o volume loss using the density of the specimen. T h e data obtained from the wear tests were presented a s wear resistance of pin sample for different treatments namely C H T , SCT and DCT. T h e wear rate is varied with the applied load and also with the sliding speed. As per the method used by R F Barron for finding out wear r e ~ i s t a n c e " ~ ' ,the influence on the wear resistance under different conditions of normal load was found out. T h e wear resistance is a non-dimensional parameter. T h e following formula was used to calculate the wear re~istance"~'.
WR=(F
v)/(W, H,)
(1)
where, W , is the wear resistance; F is the normal load, N; 'u is the linear velocity, mm/s; W , is the wear rate of pin, mm3/s; and H , is the Vickers hardness, N/mm2. The Archard wear coefficient (k) was also calculated for all the samples. The reciprocal of wear resistance is calculated from Eqn. (11, which is equal t o the Archard wear coefficient. T h e results of the average Vickers hardness values are reported in Table 2. Table 3 Conditions CHT SCT DCT
CHT SCT DCT
CHT SCT
DCT
(N
mrn-*>
Type of treatment
Hardness value
CHT SCT DCT
5 835 6 208 6 835
Microstructural study using optical microscope
T h e microstructures of C H T , SCT and DCT samples were studied through scanning electron microscope ( S E M ) . T h e samples were polished on a series of emery papers of grit 80, 120, 200, 600, 800, 10 0 0 , and up t o 1 pm. T h e n , the samples were polished by using diamond paste and finally all the samples were etched with 2% of Nital.
Results and Discussion
2 2.1
Wear tests at lower loads
T h e linear wear, tangential frictional force, wear resistance, wear coefficient and coefficient of friction for C H T , S C T and DCT samples for the applied normal load of 1 0 N , 20N and 30 N are obtained and given in Table 3 , Table 4, and Table 5 , respectively.
Wear test results at load of 10 N Average frictional force/N
Coefficient of friction
14. 1 13. 9
14
1.4
0.001758
12. 1 ll.
11.75
1. 18
0.001 176
8. 8 9. 1
8. 95
0. 90
Average frictional force/N
Coefficient of friction
Specimen
Wear/
Average
Wear
Wear
Frictional
pm
wear/pm
resistance
coefficient
force/N
c1 C2
75 83
79
390.49
0.002 560
s1
52
55 47
51
568.53
D1 D2
33 27
30
849.74
Wear test results at load of 20 N
Specimen
Wear/
Average
Wear
Wear
Frictional
identification
pm
wear/pm
resistance
coefficient
force/N
c3 c4
155 167
161
383.21
0.002 609
15. 7 15. 9
15. 8
0. 79
s3
s4
108 104
106
547.07
0.001 828
13. 8 13. 7
13.75
0. 69
D3 D4
66 60
63
809.27
0.001 236
10. 5 10. 7
10. 6
0. 53
Specimen
Wear/
Average
Wear
Wear
Frictional
identification
pm
wear/pm
resistance
coefficient
force/N
Average frictional force/N
Coefficient of friction
c5
244 246
245
377.74
0.002 647
18. 2 17. 9
18.05
0. 60
S6
157 169
163
533.65
0.001 873
16. 7 16. 3
16. 5
0. 55
D5 D6
103 99
101
757.19
0.001 321
15. 5 15. 2
15.35
0. 51
Table 5 Conditions
1.2
Vickers hardness of En 19 steel
identification
Table 4 Conditions
Table 2
55 '
C6
s5
Wear test results at load of 30 N
56
Journal of Iron and Steel Research, International
In this study of frictional behavior, the steady state was attained after approximately 100 s and the coefficient of friction was found after the steady state. This value is continuous until the end of the test. T h e coefficient of friction is dependent on the sliding velocity t o some extent. T h e frictional force a t high velocity (1. 57 m / s > was the result of asperit y deformation and the corresponding high frictional energy dissipating a t the sliding interfaceCI6'. For load of 10 N , the coefficient of friction was found t o be 1. 40 for C H T samples, 1. 18 for S C T samples, and 0. 90 for DCT samples, respectively, a s indicated in Table 3. T h e coefficient of friction has a relatively high value for the low normal load of 10 N. However, Prasanta S a h ~ o " ~reported ' that the coefficient of friction in sliding wear varies between 0. 8 and 1. 5 for the unlubricated self-mated iron steel pairs. I t is obvious that the coefficient of friction of S C T and DCT samples was lower than that of CHT samples for a normal load of 10 N. This may be contributed t o the transformation of retained austenite t o martensite along with the carbide precipitations. T h e reduction of the coefficient of friction with supplementing the cryogenic treatment is expected t o be a result of increasing the hardness and particularly compressive residual stress on the surface of the steel. Previous X-ray diffractometry studies revealed that when compared to those of C H T samples ( + 108.1 MPa), the residual stresses on surface were found t o decrease by 164% for DCT samples (-69.1 MPa) and I t proved 8 2 % for S C T samples ( +19. 6 MPa)"']. that S C T and DCT help t o reduce the residual stress on the surface of the E n 19 steel. This leads t o an increase in hardness, wear resistance, fatigue and impact resistance of the steel components. I t also gives the resistance t o the crack growth. T h e wear resistance has been increased by 45.59% for SCT samples and 117. 6 1 % for DCT samples when compared t o C H T for a n applied load of 10 N. I t also proves that the wear resistance of DCT samples is 49.46% higher than that of S C T samples for an applied load of 10 N , a s evaluated from Table 3. For a n applied load of 20 N , the coefficient of friction is reduced from 0. 79 (for C H T samples) t o 0. 69 ( f o r S C T samples) and further t o 0. 53 ( f o r DCT samples), respectively, a s given in Table 4. And the wear resistance has been increased by 42.76% for S C T samples and 111.18% for DCT samples when compared t o C H T samples. Also the wear resistance of D C T samples is 47. 92% more than that of SCT samples.
Vol. 18
-
A t a load of 30 N , the coefficient of friction is reduced from 0. 60 (for CHT samples) t o 0. 55 (for S C T samples) and further t o 0. 51 ( f o r DCT samples), a s indicated in Table 5. T h e wear resistance has been increased by 41. 27% for SCT samples and 100.46% for DCT samples when compared t o C H T samples. T h e wear resistance of DCT samples is 41. 89% higher than that of SCT samples, a s indicated in Table 5. Hence, it proves that SCT and DCT have more potential t o enhance the wear resistance of E n 19 steels than C H T . T h e Archard wear coefficient for CHT, SCT and DCT samples for the applied normal load of 10 N , 20 N and 30 N are also shown in Table 3, Table 4 and Table 5 , respectively. With an increase in applied normal load for a given sliding velocity, the wear loss increases in all the three different types of samples. These observations indicate that they abide by Archard law. I t states that the amount of wear volume is proportional t o the applied normal load and sliding distance. It is also inversely proportional t o the hardness of the surface of the material. T h e Archard wear coefficient is dimensionless and it is always less than unity. T h e dimensionless wear coefficient is of paramount importance and it gives a valuable means of comparing the severity of wear process in different systems. When the steel round cylinders are quenched, surface is always cooled faster thanthe centre and undergoes martensitic transformation first, which hardens the surface relative t o the centre['']. After cryogenic treatment, retained austenite volume a t the surface is lower than that of sub-surface resulting from non-martensite anomaly layers. Austenite volume increases up t o a few microns from the surface anomaly layer. T h e change in the microstructure with distance along a diameter is accompanied by a corresponding variation in the wear resistance of the material. Therefore, the improvement in wear resistance of both SCT and DCT samples when compared t o C H T samples decreases with a n increase in normal load and also there is a reduction in coefficient of friction with the increase in normal load for each sample respectively.
2 . 2 Wear tests at higher loads 2. 2. 1 Enhancement in wear resistance w i t h vary i n g loads at constant speed T h e wear resistance of CHT, SCT and DCT samples for the applied normal load of 60 N , 70 N and 80 N is analyzed, and the results are tabulated in Table 6.
Influence of Shallow and Deep Cryogenic Treatment on Tribological Behavior of En 19 Steel
Issue 9
Table 6 I.oad/N
60
Sliding velocity/
Wear resistance
Wear coefficient
CHT
SCT
DCT
CHT
SCT
DCT
2. 8 3. 2
22 258
86693 79740 66778
4 . 4 9 3 ~10-5 4. 7 1 1 X 1 0 - 5 5. s o x 10-5
I. 7 0 2 x 10-5 1. 8 7 9 x 10-5
1. i 5 3 x 10-5
21229 18690
58738 53208 45116
I. 2 5 4 x 10-5
2. 2 1 7 X 1 0 - 5
1 . 4 9 7 ~10-5
48154 40970 33085
67428 58144 46745
5. 2 2 2 x 10-5
2. 0 7 7 x 10-5
3. 2 3. 6
19148 16765 14080
5 . 9 6 5 ~10-5
2.441
1 . 4 8 3 ~10-5 1. 7 z o x 10-5
iozx 10-5
x 10-5
3. 0 2 3 x 10-5
2. i 3 9 x 10-5
2. 8 3. 2 3. 6
16412. 13249 11494
39159 31216 26468
56 044 44300 36985
6.093 X 10K5 7 . 5 4 8 ~10-5
2 . 5 5 4 ~10-5 3. 2 0 3 x 10-5 3 . 7 7 8 ~10-5
2. 2 5 7 x 10-5
2. 8
80
Wear test results at higher loads
( m * s-')
3. 6 70
57
T h e wear resistance has been increased by 164% for SCT samples and 289% for DCT samples when compared to C H T samples with an applied normal load of 60 N at a sliding speed of 2.8 m/s. For an applied load of 70 N at sliding speed of 2.8 m/s, the wear resistance has been enhanced by 151% for SCT samples and 252% for DCT samples when compared to- C H T samples. At a load of 80 N , the wear resistance of SCT and DCT samples is 139% and 241% more than that of C H T , respectively. It proves that at higher normal loads, the improvements in wear resistance of SCT and DCT with respect to that C H T decreases with increasing load at a sliding speed of 2 .8 m/s. For a load of 60 N a t a sliding speed of 3. 2 m/s, the wear resistance of SCT and DCT samples was 151% and 276 % higher than that of C H T samples, respectively. For a load of 70 N , the wear resistance of SCT and DCT sample is 144% and 247% more than that of C H T samples, respectively. It is found that at a load of 80 N and a sliding speed of 3. 2 m/s, the wear resistance of SCT and DCT samples is 136% and 234% more than that of C H T samples, respectively. The improvement in wear resistance of SCT and DCT samples with respect t o that of C H T samples decreases when the load increases at a sliding speed of 3. 2 m/s. At a load of 60 N and a sliding speed of 3.6 m/s, the wear resistance has been increased by 141% for SCT samples and 257% for DCT samples with respect to C H T samples. The wear resistance of SCT and DCT samples is 135% and 232% for an applied load of 70 N , respectively. At a load of 80 N , the wear resistance of SCT and DCT samples is 130% and 222% more than that of CHT, respectively. The enhancement in wear resistance of SCT and DCT samples with respect to that of C H T samples decreases as the load increases.
7.
8.700X
1 . 7 8 4 ~10-5 2 . 7 0 4 ~10-5
The variations of wear coefficient in the samples of C H T , SCT and DCT for the applied normal load of 60 N , 70 N and 80 N at a sliding speed of 2.8 m/s, 3.2 m/s and 3. 6 m/s are also indicated in Table 6. With an increase in applied normal load for a given sliding speed, the wear loss increases in all the C H T , SCT and DCT samples. 2. 2. 2 Enhancement in wear resistance w i t h varying speed at constant load The wear resistance of all the C H T , SCT and DCT samples at different sliding speeds with a load of 60 N is also analyzed from Table 6. A t a load of 60 N , the wear resistance of SCT and DCT samples with respect to that of C H T samples decreases with an increase in the sliding speed. It proves that the development of wear resistance of all the SCT and DCT samples with a load of 70 N and 80 N decreases with the increase in sliding speed. Finally, the above study reveals that the enhancements in wear resistance of SCT and DCT samples compared to that of C H T samples decreases with an increase in load under the same condition of sliding speed and decreases with an increase in sliding speed under identical condition of load.
2.3
Microstructure analysis Previous studies report the retained austenite present in the samples of En 19 steel when subjected to C H T , SCT and DCT using X-ray diffraction techniques. After C H T of steel samples, there is 6. 5% of retained austenite. The sample after SCT results in the reduction of retained austenite from 6. 5% to 5. 1%. The sample after DCT results in a further reduction of retained austenite from 6. 5% ( C H T ) to 2.7%. The reduction of retained austenite content in the SCT and DCT samples shows that cryogenic treatment promotes the transformation of retained austenite into martensite. This causes an increase in
58
J o u r n a l of Iron a n d S t e e l R e s e a r c h , International
wear resistance of En 19 steels. The microstructural studies of the treated samples were carried out to see if any significant change occurred. Fig. 2 shows the SEM micrographs of C H T , SCT and DCT samples. There are no microstructural changes observed between CHT, SCT and DCT samples. That is, no
~~~~
Fig. 2
3
~
~~
Microstructure of CHT sample ( a ) , SCT sample (b) , and DCT sample (19
Conclusions
cryogenic treatment promote the transformation of retained austenite to martensite, thereby causing a significant increase in wear resistance. 2 ) Wear resistance has been increased by 118. 38% for SCT samples and 214.94% for DCT samples when compared to C H T samples. In addition, the increase in wear resistance of DCT samples is 44.39% with respect to SCT samples. 3 ) Wear is increased linearly with respect t o load at constant sliding velocity. T h e wear is also increased linearly with respect to sliding velocity at constant applied load. 4) T h e lowest coefficient of friction is obtained in DCT samples treated at -196 "C for 24 h. 5) T h e improvements in wear resistance of both SCT and DCT samples with respect to C H T samples decreases with increasing load and also there is a reduction in coefficient of friction with the increasing load for each sample.
T h e authors wish to thank Professor M Pellizzari o f Department o f Materials Engineering and Industrial Technologies, University o f Trento , I t a l y f o r having extended his rnetallurgical facilities f o r the successful completion o f work. References:
[S]
appreciable difference could be detected by SEM owing to small amount (less than 1 0 % ) of retained auspointed out that tenite"". However, J Y Huang et alCzo1 the precipitation of fine carbides and the transformation of retained austenite into martensite contribute to the improvement of wear resistance.
~~~~
1) Both deep cryogenic treatment and shallow
[I]
Vol. 18
Dunn D J. Metal Removal Mechanisms Comprising Wear in Mineral Processing [C] // Ludema K C. Proceedings of International Conference on Wear of Materials. New York: ASME International, 1985: 2417. T a o D, Blue C , Dahotre N B, et al. High-Density-Infrared (HDI) Treatment of Mineral Processing Equipment for En-
hanced Wear Resistance [J]. Minerals Engineering, 2006, 19 (2): 190. Leskovsek V, Kalin M, Vizintin J. Influence of Deep-Cryogenic Treatment on Wear Resistance of Vacuum Heat-Treated HSS [J]. Vacuum, 2006, 80(6): 507. Barron R F. Effect of Cryogenic Treatment on Lathe Tool Wear [J]. Progress in Refrigeration Science and Technology, 1973, 1: 529. LIU Hao-huai, WANG Jun, S H E N Bao-luo, et al. Effects of Deep Cryogenic Treatment on Property of 3Cr13MolVl. 5 High Chromium Cast Iron [J]. Materials and Design, 2007, 28 (3) : 1059. Yong A Y L , Seah K H W, Rahman M. Performance Evaluation of Cryogenically Treated Tungsten Carbide Tools in Turning [J]. International Journal of Machine Tools and Manufae ture, 2006, 46(15): 2051. Mohanlal D, Renganarayanan S, Kalanidhi A. Cryogenic Treatment to Augment Wear Resistance of Tool and Die Steels [J]. Cryogenics, 2001, 41(3): 149. Collins D N , Dormer J. Deep Cryogenic Treatment of a D2 Cold-Work Tool Steel [J]. Heat Treatment of Metals, 1997, 3: 71. Molinari M , Pellizzari M , Gialanella S, et al. Effect of Deep Cryogenic Treatment on the Mechanical Properties of Tool Steels [J]. Journal of Materials Processing Technology, 2001, 118(1/2/3): 350. Preciado M, Bravo P M, Alegre J M. Effect of Low Temperature Tempering Prior Cryogenic Treatment on Carburized Steels [J]. Journal of Materials Processing Technology, 2006, 176(1/2/3): 41. Zhirafar S, Rezaeian A , Pugh M. Effect of Cryogenic Treatment on the Mechanical Properties of 4340 Steel [J]. Journal of Materials Processing Technology, 2007, 186(1/2/3) : 298. Bensely A , Senthilkumar D, Mohanlal D, et al. Effect of C r y ogenic Treatment on Tensile Behavior of Case Carburized Steel-815M17 [J]. Materials Characterization, 2007. 58(5) : 485. Xu L , Vose C, S t John D. Abrasive Wear Study of Selected White Cast Irons a s Liner Materials for the Mining Industry [J]. Wear, 1993, 162-164(Part 2): 820. ASTM Standards. G99-05, Standard Test Methods for Wear Testing With a Pin on Disk Apparatus [S]. New York: ASM International, 2005.
Issue 9 [15]
[16]
[17]
Influence of Shallow and Deep Cryogenic Treatment on Tribological Behavior of En 19 Steel Barron RF. Do Treatments at Temperature Below -120 'F Help Increase the Wear Resistance of Tool Steels? Here are Some Research Findings That They Do [J]. Heat Treating, 1974, 5: 14. Li J , Sheng X H. Nan0 Tribology Characteristics of Ti02 Films on 3-Mercaptopropyl Trimethoxysilane .Sulfonated SelfAssembled Monolayer [J]. Bulletins of Material Science, 2009, 32(5): 481. Prasanta S. Engineering Tribology [MI. New Delhi: Prentice Hall of India, 2008.
[18]
[19]
[20]
' 59 '
Senthilkumar D, Rajendran I , Pellizzari M , et al. Influence of Shallow and Deep Cryogenic Treatment on the Residual State of Stress of 4140 Steel [J]. Journal of Materials Processing Technology, 2011, 211(3): 396. Robert E, Reed-Hill, Reza Abbaschian. Physical Metallurgy Principle [MI. 3rd ed. Singapore: Thomson Asia Pte Ltd, 2003. Huang J Y, Zhu Y T, Liao X Z, et al. Microstructure of Cryogenic Treated M2 Tool Steel [J]. Materials Science and Engineering, 2003, 339A(1/2): 241.