- Email: [email protected]
Effect of Sinter Hardening on Microstructure and Mechanical Properties of Astaloy 85Mo
Available online at www.sciencedirect.com
.-",
....; dI
ScienceDirect
JOURNAL OF IRON AND STEEL RESEARCH, INTERNATIONAL. 2012, 19(10): 43-46
Effect of Sinter Hardening on Microstructure and Mechanical Properties of Astaloy 85Mo K Sheikhi Moghaddarn",
M Ghambari",
H Farhangi",
N Solirnanjad"
O. School of Metallurgy and Materials Engineering, College of Engineering University of Tehran, Tehran 11155-4563, Iran; 2. Hoganas AB, Hoganas SE-263 83, Sweden) Abstract: Effect of sinter hardening on the microstructure, density, hardness and tensile properties of Astaloy 85Mo+ 0.7% graphite was investigated. For this purpose, Astaloy 85Mo, a pre-alloyed powder, was mixed with 0.7% UF4 graphite and then pressed in single action die and sintered at 1120 'C for 30 min in N z-10 % Hz atmosphere. Then samples were cooled from O. 5 to 3 'C / s sintering temperature in accordance with different cooling rates. The difference in microstructure, hardness, density and tensile properties of the samples associated with different cooling rates from sintering temperature has been investigated. The results show that the microstructure remains bainitic by changing cooling rate, but it becomes finer and then the hardness and tensile strength of the samples will increase by increasing the cooling rate from sintering temperature. Key words: sinter hardening; Astaloy 85Mo; cooling rate; bainitic microstructure
The rapid development of the automotive industry and focus on production costs present a great increase in the application of high performance powder metallurgy parts and exploit a great market of ironbased PM materials'<". However, conventional sintered powder metallurgy parts generally have more than 5% percent porosity in volume. Enhanced sintering techniques can be applied to obtain higher densities and improved properties in the sintered parts[Z-4]. In general, there are two ways to increase density and performance of PM parts: one is attaining high density by modification of pressing and sintering processes and the other one is using sintering enhancer by addition of certain elements[S-6]. Today, a new method of sinter hardening is added to the list above. Sinter hardening usually refers to the process of a part cooling from the sintering temperature at a sufficient rate to transform a significant portion of the material matrix to martensite. Interest in sinter hardening has grown because it offers good manufacturing economy by providing one step process and a unique combination of strength, toughness, and hardness-". By accelerating the post sintering cooling rate, the quantity of martensite can be increased which results in increased strength and hardness-'". The amount of marBiography.K Sheikhi Moghaddamt l sdu-r-) , Male. Doctor;
tensite present in a material is dependent not only on the cooling rate, but also on the alloying element content, mass, density and geometry of a part. Alloying elements such as chromium, molybdenum, manganese, nickel and copper increase the hardenability or the ability of a material to form martensite when cooled from a temperature in the austenitic region[9]. In nickel containing systems, heat treatment of admixed nickel materials or sinter hardening of diffusion bonded or pre-alloyed materials are often used to maximize the performance of the material system-I'", Chromium base materials have also shown good sinter hardening characteristics[ll]. To optimize manufacturing costs and performance of sinter hardened parts, the combined effects of alloying elements, their content and the base powder on compressibility and hardenability must be properly analyzed and balanced'V". Many sinter hardenable powder metallurgy materials[13-1S] have been developed over the past few decades and commonly used Fe-Cu-Ni-Mo-C system has exhibited good dynamic and static properties[lS-17]. By controlling the post sintering cooling rate, the microstructure can be manipulated to form the required amount of martensite to obtain the desired mechanical properties. By increas-
E-mail: [email protected];
Received Date: June 11, 2011
Vol. 19
Journal of Iron and Steel Research. International
• 44 •
ing the hardenability of the materials large amounts of martensite still can be obtained also at lower cooling rates[18J. The aim of this paper is to investigate the effects of sinter hardening on the microstructure and mechanical properties of Astaloy 85Mo+0. 7%C. It shows that how changes in microstructure, affect the density, hardness and tensile properties of the samples. The originality of the present work is the determination of the microstuctural and mechanical behavior of Astaloy 85Mo compacts subjected to sinter hardening and this is the first time that the effect of sinter hardening on the properties of Astaloy 85Mo has been investigated.
1
Experimental Procedure
The material studied was pre-alloyed Astaloy 85Mo supplied by Hoganas Sweden, mixed with 0.7% UF4 graphite. The chemical composition of the powder is given in Table 1. The physical properties of the powder are given in Table 2. Table 1
Slow cooling
Chemical composition of Astaloy 85Mo (mass percent. %)
Mo
c
Fe
0.85
0.7
Balance
Table 2
Fig. 1 Dimensions of tensile samples according to MPIF 10 standard
Physical properties of Astaloy 85Mo
Properties
Value
Flow hall
25 s/50 g
Apparent density
3.1 g. cm- 3
Green density
7.15 g. cm ""
The samples were pressed by single action pressing and then sintered at 1120 "C for 30 min in a N z-10 % Hz reducing atmosphere. Fig. 1 shows the dimensions and schematic picture of the pressed samples , according to MPIF 10 standard. Sinter hardening was carried out on some samples using air circulation. The cooling rates of 2 and 3 "C / s were chosen for the sinter hardening process. Fig. 2 shows the sequence of sintering and sinter hardening-'I". The samples were stress relieved at 200 "C in the furnace for 1 h after being sintered hardened. The rate of O. 5 "C / s was for the normal cooling in the furnace. The microstructures of the samples were investigated using an optical microscope after etching with Nital 3 % etchant and the percentage of different phases was measured by image analysis technique. Hardness of the samples was measured according to ASTM E92. Densities of the samples were measured
Fig. 2
Sequence of sintering and sinter hardening
according to MPIF 42 standard. Tensile strength and yield strength of the samples at various cooling rates were measured according to MPIF 10 standard, as mentioned before.
2
Results and Discussion
Fig. 3 shows the microstructure of the samples at different cooling rates. It can be seen that the microstructure of sintered sample is bainitic. As the cooling rate from sintering temperature increases from O. 5 to 2 and 3 "C / s , the microstructure remains almost bainitic , but the bainitic structure becomes finer, as can be seen in Fig. 3 (b) and (c). So increasing the cooling rate from O. 5 to 3 "C / s is not enough for Astaloy 85Mo+ O. 7 % C to form martensite, although in some area of the sinter hardened sample with cooling rate of 3 "C / s , martensitic areas were detected (less than 1 % according to the report of image analyzer). In order to assess the quality of sintering and sinter hardening and make sure that no decarburization has happened during sintering and sinter hardening, carbon and oxygen analyses on the sample were done after sintering and the results are presented in Table 3. As it can be seen, no decarburization occurred during sintering.
Issue 10
(a) 0.5 'C/s;
Fig. 3 Table 3
• 45 •
Effect of Sinter Hardening on Microstructure and Mechanical Properties of Astaloy 85Mo
(b) 2 'C/s;
(c) 3 ·C/s.
Microstructure of Astaloy 85Mo samples with different cooling rates 600 , . . . - - - - - - - - - - - - - - - - - ,
Oxygen and carbon analysis of sinter hardened sample at different cooling rates
Item
0.5 'C/s
2 'C/s
3 'C/s
C/%
0.7
O. 7
0.69
01%
0.02098
0.02151
O. 02364
;
400
~ 200
Table 4 shows the changes in density of the samples, as a function of cooling rate. As mentioned before, since no phase transformation occurred in the samples while increasing the cooling rate from sintering temperature, it is expected that no significant change in density of the samples is detected and this is confirmed by Table 4. It can be said that density is independent of the cooling rate and a good reason for this fact is the constant microstructure of the samples in different cooling rates. Table 4 Density, hardness and tensile properties of Astaloy 85Mo as a function of cooling.rate 0.5 'C/s
2 'C/s
3 'C/s
Density/(g· cm- 3 )
7.12
7.11
7.11
Hardnessl (HV10)
159
161
206
R,/MPa Rm/MPa
409
411
499
435
456
530
Item
As it was seen in Fig. 3, the microstructure remains nearly unchanged by increasing the cooling rate, although the microstructure becomes finer as the cooling rate increases, especially at cooling rate of 3 'C/ s. The results show that hardness of the samples increases from 159 to 206 HV10 by increasing the cooling rate from o. 5 to 3 'C/ s which is about 30 % increase in hardness. Table 4 shows the changes in hardness as a function of cooling rate. So it can be said that changing the phases in the microstructure is not the only way of increasing the hardness. Obtaining finer microstructure, increasing the cooling rate also leads to increase of the hardness. Fig. 4 shows the stress-strain curve for the sam-
.0.5 'tIs
.2 t;/s "':3 'tIs 0.2
()
Fig. 4
0.4
e
0.6
0.8
Stress-strain curve for samples at different cooling rates
ples at various cooling rates. It is clearly understood from Fig. 4 that increasing the cooling rate from sintering temperature, the yield strength and tensile strength are increased, while the elongation is reduced. To investigate it in more details, the magnitude of yield strength and tensile strength are calculated as a function of cooling rate from sintering temperature and are presented in Table 4. It can be seen that increasing the cooling rate from O. 5 to 3 'C / s increases the yield strength and tensile strength from 410 to 500 MPa and 435 to 530 MPa, respectively. It means that by increasing cooling rate from O. 5 to 3 'C/ s , both yield strength and tensile strength are increased by about 22 %. The reason for this phenomenon is the finer bainitic structure in sinter hardened samples, as mentioned before. The finer the bainitic structure, the lesser is the distance between adjacent ferrite and cementite planes and hence more obstacles can lock the dislocations and that's the reason for increasing in hardness, yield strength and tensile strength of the samples.
3
Conclusions
1) By increasing the cooling rate from O. 5 to 3 'C/ s , the bainitic microstructure of Astaloy 85Mo O. 7 %c remains nearly unchanged and it just becomes finer
+
• 46 •
Journal of Iron and Steel Research. International
as a result of increasing cooling rate. The cooling rate of 3 'C / s is not fast enough to produce a martensitic structure in these samples. 2) The densities of the samples have almost no change while increasing the cooling rate from sintering temperature. as a result of the same phase structure in all cooling rates. 3) The hardness of the samples Astaloy 85Mo + o. 7%C is increased from 159 to 206 HV10 (about 30%) by increasing the cooling rate from O. 5 to 3 'C / s. 4) Yield stress and tensile strength of Astaloy 85Mo+0. 7%C increase from 410 to 500 MPa and 435 to 530 MPa respectively. as the cooling rate from sintering temperature increases from O. 5 to 3 'C / s, References : [lJ
[2J
[3J
[4J
[5J [6J
[7J
[8J
Bocchini G F, Rivolta B, Silva G. et al. Influence of Cooling Rate on Microstructural and Mechanical Properties of Alloys From Diffusion-Bonded Powders, Sintered in Different Conditions [1]. Powder Metal Sci and Tech. 2002. 4: 16. Madan 0 S, German R M. Structural-Property Relationship in Iron Powder Compacts Alloyed With Boron [CJ II Gasbarre T G, Jandeska W F. Advances in Powder Metallurgy and Particulate Materials. Princeton, San Diego: Metal Powder Industries Federation, 1989: 45. Selecka A, Salak A. Danninger H. The Effect of Boron Liquid Phase Sintering on Properties of Ni-, Mo- and Cr-Alloyed Structural Steels [J]. J Mater Process Technol , 2003, 141: 379. Liu J, Cardamone A. Potter T, et al. Liquid Phase Sintering of Iron-Carbon Alloys With Boron Additions [1]. Powder Metall , 2000, 43: 57. Yang X. Guo S J. Fe-Mo-B Enhanced Sintering of PIM 316L Stainless Steel [1]. J Iron Steel Res Int , 2008, 15(1): 10. Sarasola M. Gomez-Acebo T. Castro F. Liquid Generation During Sintering of Fe-3. 5%Mo Powder Compacts [JJ. Powder Metallurgy. 2005. 48(1): 59. Baran M C. Graham A H, Davala A B, et al. Sinter Hardenable Material [CJlllnternational Conference on Powder Metallurgy and Particulate Materials. Vancouver: MPIF. 1999: 43. Engstrom U, McLelland J, Maroli B. Effect of Sinter Harden-
[9J
[10J
[l1J
[12J
[13J
[14J [15J
[16J
[17J
[18J
[19J
Vol. 19
ing on the Properties of High Temperature Sintered PM Steels [cJ II World Congress on Powder Metallurgy and Particulate Materials. Orlando: MPIF. 2002, 267. Maroli B. Berg S. Larsson M. et al. Performance of Sinter Hardened PIM Steels [CJIIEuropean Conference on Advanced Materials and Processes. Rimini , AIM. 2001: 157. Schmidt M. Effect of Sintering Time and Cooling Rate on Sinter Hardenable Materials [CJ II World Congress on Powder Metallurgy and Particulate Materials. Las Vegas: MPIF. 2004: 89. Larsson M. Properties of Cr-Alloyed PM Materials [CJIISalgado L. Filho F A. International Latin-American Conference on Powder Technology. Sao Paulo, Materials Science Forum. 2003: 436. Bocchini G F. Rivolta B. Silva G. lit al. Microstructural and Mechanical Characterization of Some Sinter Hardening Alloys and Comparisons With Heat Treated PM Steels [1]. Powder Met. 2004. 47: 343. Chagon F. Trudel Y. Effect of Density on Mechanical Properties of Sinter Hardened PIM Materials [CJ /1 Advances in Powder Metallurgy and Particulate Materials. Princeton: MPIF. 1996: 211. Rui-jin G. Low Alloy Steels for Sinter Hardening UJ. J PRWder Metall Int. 2003. 13: 1. Hironori S, Masaaki S. Masaki Y, et al. Sinter Hardening Properties of Pre-Alloyed Powder [CJ II Advances in Powder Metallurgy and Particulate Materials. Princeton: MPIF, 2000: 125. Chawala N. Murphy T F. Narasimhan K S. et al. Axial Fatigue Behavior of Binder-Treated Versus Diffusion Alloyed Powder Metallurgy Steels [1]. J Mater Sci Eng. 2001. 308A: 180. XIAO Zhi-yu , ZHANG Juhong , WU Yuan-biao , et al. Influence of Sintering Parameters on Tensile Strength of Warm Compacted Fe-2Ni-2Cu-1Mo-1C Material [1]. Chinese J Nonferrous Met. 2006. 168: 1326 (in Chinese). Engstrom U. Frykholm R. Milligan D. et al. Cost Effective Materials for Sinter Hardening Applications [CJlllnternational Conference on Powder Metallurgy and Particulate Materials. Washington: MPIF. 2008: 342.
fillllri G. Causton R. Lawley A. Effect of Cooling Rates During Sinter Hardening [CJ II International Conference on Powder Metallurgy and particulate Materials. Las Vegas: MPIF. 2003, 174.
.-",
....; dI
ScienceDirect
JOURNAL OF IRON AND STEEL RESEARCH, INTERNATIONAL. 2012, 19(10): 43-46
Effect of Sinter Hardening on Microstructure and Mechanical Properties of Astaloy 85Mo K Sheikhi Moghaddarn",
M Ghambari",
H Farhangi",
N Solirnanjad"
O. School of Metallurgy and Materials Engineering, College of Engineering University of Tehran, Tehran 11155-4563, Iran; 2. Hoganas AB, Hoganas SE-263 83, Sweden) Abstract: Effect of sinter hardening on the microstructure, density, hardness and tensile properties of Astaloy 85Mo+ 0.7% graphite was investigated. For this purpose, Astaloy 85Mo, a pre-alloyed powder, was mixed with 0.7% UF4 graphite and then pressed in single action die and sintered at 1120 'C for 30 min in N z-10 % Hz atmosphere. Then samples were cooled from O. 5 to 3 'C / s sintering temperature in accordance with different cooling rates. The difference in microstructure, hardness, density and tensile properties of the samples associated with different cooling rates from sintering temperature has been investigated. The results show that the microstructure remains bainitic by changing cooling rate, but it becomes finer and then the hardness and tensile strength of the samples will increase by increasing the cooling rate from sintering temperature. Key words: sinter hardening; Astaloy 85Mo; cooling rate; bainitic microstructure
The rapid development of the automotive industry and focus on production costs present a great increase in the application of high performance powder metallurgy parts and exploit a great market of ironbased PM materials'<". However, conventional sintered powder metallurgy parts generally have more than 5% percent porosity in volume. Enhanced sintering techniques can be applied to obtain higher densities and improved properties in the sintered parts[Z-4]. In general, there are two ways to increase density and performance of PM parts: one is attaining high density by modification of pressing and sintering processes and the other one is using sintering enhancer by addition of certain elements[S-6]. Today, a new method of sinter hardening is added to the list above. Sinter hardening usually refers to the process of a part cooling from the sintering temperature at a sufficient rate to transform a significant portion of the material matrix to martensite. Interest in sinter hardening has grown because it offers good manufacturing economy by providing one step process and a unique combination of strength, toughness, and hardness-". By accelerating the post sintering cooling rate, the quantity of martensite can be increased which results in increased strength and hardness-'". The amount of marBiography.K Sheikhi Moghaddamt l sdu-r-) , Male. Doctor;
tensite present in a material is dependent not only on the cooling rate, but also on the alloying element content, mass, density and geometry of a part. Alloying elements such as chromium, molybdenum, manganese, nickel and copper increase the hardenability or the ability of a material to form martensite when cooled from a temperature in the austenitic region[9]. In nickel containing systems, heat treatment of admixed nickel materials or sinter hardening of diffusion bonded or pre-alloyed materials are often used to maximize the performance of the material system-I'", Chromium base materials have also shown good sinter hardening characteristics[ll]. To optimize manufacturing costs and performance of sinter hardened parts, the combined effects of alloying elements, their content and the base powder on compressibility and hardenability must be properly analyzed and balanced'V". Many sinter hardenable powder metallurgy materials[13-1S] have been developed over the past few decades and commonly used Fe-Cu-Ni-Mo-C system has exhibited good dynamic and static properties[lS-17]. By controlling the post sintering cooling rate, the microstructure can be manipulated to form the required amount of martensite to obtain the desired mechanical properties. By increas-
E-mail: [email protected];
Received Date: June 11, 2011
Vol. 19
Journal of Iron and Steel Research. International
• 44 •
ing the hardenability of the materials large amounts of martensite still can be obtained also at lower cooling rates[18J. The aim of this paper is to investigate the effects of sinter hardening on the microstructure and mechanical properties of Astaloy 85Mo+0. 7%C. It shows that how changes in microstructure, affect the density, hardness and tensile properties of the samples. The originality of the present work is the determination of the microstuctural and mechanical behavior of Astaloy 85Mo compacts subjected to sinter hardening and this is the first time that the effect of sinter hardening on the properties of Astaloy 85Mo has been investigated.
1
Experimental Procedure
The material studied was pre-alloyed Astaloy 85Mo supplied by Hoganas Sweden, mixed with 0.7% UF4 graphite. The chemical composition of the powder is given in Table 1. The physical properties of the powder are given in Table 2. Table 1
Slow cooling
Chemical composition of Astaloy 85Mo (mass percent. %)
Mo
c
Fe
0.85
0.7
Balance
Table 2
Fig. 1 Dimensions of tensile samples according to MPIF 10 standard
Physical properties of Astaloy 85Mo
Properties
Value
Flow hall
25 s/50 g
Apparent density
3.1 g. cm- 3
Green density
7.15 g. cm ""
The samples were pressed by single action pressing and then sintered at 1120 "C for 30 min in a N z-10 % Hz reducing atmosphere. Fig. 1 shows the dimensions and schematic picture of the pressed samples , according to MPIF 10 standard. Sinter hardening was carried out on some samples using air circulation. The cooling rates of 2 and 3 "C / s were chosen for the sinter hardening process. Fig. 2 shows the sequence of sintering and sinter hardening-'I". The samples were stress relieved at 200 "C in the furnace for 1 h after being sintered hardened. The rate of O. 5 "C / s was for the normal cooling in the furnace. The microstructures of the samples were investigated using an optical microscope after etching with Nital 3 % etchant and the percentage of different phases was measured by image analysis technique. Hardness of the samples was measured according to ASTM E92. Densities of the samples were measured
Fig. 2
Sequence of sintering and sinter hardening
according to MPIF 42 standard. Tensile strength and yield strength of the samples at various cooling rates were measured according to MPIF 10 standard, as mentioned before.
2
Results and Discussion
Fig. 3 shows the microstructure of the samples at different cooling rates. It can be seen that the microstructure of sintered sample is bainitic. As the cooling rate from sintering temperature increases from O. 5 to 2 and 3 "C / s , the microstructure remains almost bainitic , but the bainitic structure becomes finer, as can be seen in Fig. 3 (b) and (c). So increasing the cooling rate from O. 5 to 3 "C / s is not enough for Astaloy 85Mo+ O. 7 % C to form martensite, although in some area of the sinter hardened sample with cooling rate of 3 "C / s , martensitic areas were detected (less than 1 % according to the report of image analyzer). In order to assess the quality of sintering and sinter hardening and make sure that no decarburization has happened during sintering and sinter hardening, carbon and oxygen analyses on the sample were done after sintering and the results are presented in Table 3. As it can be seen, no decarburization occurred during sintering.
Issue 10
(a) 0.5 'C/s;
Fig. 3 Table 3
• 45 •
Effect of Sinter Hardening on Microstructure and Mechanical Properties of Astaloy 85Mo
(b) 2 'C/s;
(c) 3 ·C/s.
Microstructure of Astaloy 85Mo samples with different cooling rates 600 , . . . - - - - - - - - - - - - - - - - - ,
Oxygen and carbon analysis of sinter hardened sample at different cooling rates
Item
0.5 'C/s
2 'C/s
3 'C/s
C/%
0.7
O. 7
0.69
01%
0.02098
0.02151
O. 02364
;
400
~ 200
Table 4 shows the changes in density of the samples, as a function of cooling rate. As mentioned before, since no phase transformation occurred in the samples while increasing the cooling rate from sintering temperature, it is expected that no significant change in density of the samples is detected and this is confirmed by Table 4. It can be said that density is independent of the cooling rate and a good reason for this fact is the constant microstructure of the samples in different cooling rates. Table 4 Density, hardness and tensile properties of Astaloy 85Mo as a function of cooling.rate 0.5 'C/s
2 'C/s
3 'C/s
Density/(g· cm- 3 )
7.12
7.11
7.11
Hardnessl (HV10)
159
161
206
R,/MPa Rm/MPa
409
411
499
435
456
530
Item
As it was seen in Fig. 3, the microstructure remains nearly unchanged by increasing the cooling rate, although the microstructure becomes finer as the cooling rate increases, especially at cooling rate of 3 'C/ s. The results show that hardness of the samples increases from 159 to 206 HV10 by increasing the cooling rate from o. 5 to 3 'C/ s which is about 30 % increase in hardness. Table 4 shows the changes in hardness as a function of cooling rate. So it can be said that changing the phases in the microstructure is not the only way of increasing the hardness. Obtaining finer microstructure, increasing the cooling rate also leads to increase of the hardness. Fig. 4 shows the stress-strain curve for the sam-
.0.5 'tIs
.2 t;/s "':3 'tIs 0.2
()
Fig. 4
0.4
e
0.6
0.8
Stress-strain curve for samples at different cooling rates
ples at various cooling rates. It is clearly understood from Fig. 4 that increasing the cooling rate from sintering temperature, the yield strength and tensile strength are increased, while the elongation is reduced. To investigate it in more details, the magnitude of yield strength and tensile strength are calculated as a function of cooling rate from sintering temperature and are presented in Table 4. It can be seen that increasing the cooling rate from O. 5 to 3 'C / s increases the yield strength and tensile strength from 410 to 500 MPa and 435 to 530 MPa, respectively. It means that by increasing cooling rate from O. 5 to 3 'C/ s , both yield strength and tensile strength are increased by about 22 %. The reason for this phenomenon is the finer bainitic structure in sinter hardened samples, as mentioned before. The finer the bainitic structure, the lesser is the distance between adjacent ferrite and cementite planes and hence more obstacles can lock the dislocations and that's the reason for increasing in hardness, yield strength and tensile strength of the samples.
3
Conclusions
1) By increasing the cooling rate from O. 5 to 3 'C/ s , the bainitic microstructure of Astaloy 85Mo O. 7 %c remains nearly unchanged and it just becomes finer
+
• 46 •
Journal of Iron and Steel Research. International
as a result of increasing cooling rate. The cooling rate of 3 'C / s is not fast enough to produce a martensitic structure in these samples. 2) The densities of the samples have almost no change while increasing the cooling rate from sintering temperature. as a result of the same phase structure in all cooling rates. 3) The hardness of the samples Astaloy 85Mo + o. 7%C is increased from 159 to 206 HV10 (about 30%) by increasing the cooling rate from O. 5 to 3 'C / s. 4) Yield stress and tensile strength of Astaloy 85Mo+0. 7%C increase from 410 to 500 MPa and 435 to 530 MPa respectively. as the cooling rate from sintering temperature increases from O. 5 to 3 'C / s, References : [lJ
[2J
[3J
[4J
[5J [6J
[7J
[8J
Bocchini G F, Rivolta B, Silva G. et al. Influence of Cooling Rate on Microstructural and Mechanical Properties of Alloys From Diffusion-Bonded Powders, Sintered in Different Conditions [1]. Powder Metal Sci and Tech. 2002. 4: 16. Madan 0 S, German R M. Structural-Property Relationship in Iron Powder Compacts Alloyed With Boron [CJ II Gasbarre T G, Jandeska W F. Advances in Powder Metallurgy and Particulate Materials. Princeton, San Diego: Metal Powder Industries Federation, 1989: 45. Selecka A, Salak A. Danninger H. The Effect of Boron Liquid Phase Sintering on Properties of Ni-, Mo- and Cr-Alloyed Structural Steels [J]. J Mater Process Technol , 2003, 141: 379. Liu J, Cardamone A. Potter T, et al. Liquid Phase Sintering of Iron-Carbon Alloys With Boron Additions [1]. Powder Metall , 2000, 43: 57. Yang X. Guo S J. Fe-Mo-B Enhanced Sintering of PIM 316L Stainless Steel [1]. J Iron Steel Res Int , 2008, 15(1): 10. Sarasola M. Gomez-Acebo T. Castro F. Liquid Generation During Sintering of Fe-3. 5%Mo Powder Compacts [JJ. Powder Metallurgy. 2005. 48(1): 59. Baran M C. Graham A H, Davala A B, et al. Sinter Hardenable Material [CJlllnternational Conference on Powder Metallurgy and Particulate Materials. Vancouver: MPIF. 1999: 43. Engstrom U, McLelland J, Maroli B. Effect of Sinter Harden-
[9J
[10J
[l1J
[12J
[13J
[14J [15J
[16J
[17J
[18J
[19J
Vol. 19
ing on the Properties of High Temperature Sintered PM Steels [cJ II World Congress on Powder Metallurgy and Particulate Materials. Orlando: MPIF. 2002, 267. Maroli B. Berg S. Larsson M. et al. Performance of Sinter Hardened PIM Steels [CJIIEuropean Conference on Advanced Materials and Processes. Rimini , AIM. 2001: 157. Schmidt M. Effect of Sintering Time and Cooling Rate on Sinter Hardenable Materials [CJ II World Congress on Powder Metallurgy and Particulate Materials. Las Vegas: MPIF. 2004: 89. Larsson M. Properties of Cr-Alloyed PM Materials [CJIISalgado L. Filho F A. International Latin-American Conference on Powder Technology. Sao Paulo, Materials Science Forum. 2003: 436. Bocchini G F. Rivolta B. Silva G. lit al. Microstructural and Mechanical Characterization of Some Sinter Hardening Alloys and Comparisons With Heat Treated PM Steels [1]. Powder Met. 2004. 47: 343. Chagon F. Trudel Y. Effect of Density on Mechanical Properties of Sinter Hardened PIM Materials [CJ /1 Advances in Powder Metallurgy and Particulate Materials. Princeton: MPIF. 1996: 211. Rui-jin G. Low Alloy Steels for Sinter Hardening UJ. J PRWder Metall Int. 2003. 13: 1. Hironori S, Masaaki S. Masaki Y, et al. Sinter Hardening Properties of Pre-Alloyed Powder [CJ II Advances in Powder Metallurgy and Particulate Materials. Princeton: MPIF, 2000: 125. Chawala N. Murphy T F. Narasimhan K S. et al. Axial Fatigue Behavior of Binder-Treated Versus Diffusion Alloyed Powder Metallurgy Steels [1]. J Mater Sci Eng. 2001. 308A: 180. XIAO Zhi-yu , ZHANG Juhong , WU Yuan-biao , et al. Influence of Sintering Parameters on Tensile Strength of Warm Compacted Fe-2Ni-2Cu-1Mo-1C Material [1]. Chinese J Nonferrous Met. 2006. 168: 1326 (in Chinese). Engstrom U. Frykholm R. Milligan D. et al. Cost Effective Materials for Sinter Hardening Applications [CJlllnternational Conference on Powder Metallurgy and Particulate Materials. Washington: MPIF. 2008: 342.
fillllri G. Causton R. Lawley A. Effect of Cooling Rates During Sinter Hardening [CJ II International Conference on Powder Metallurgy and particulate Materials. Las Vegas: MPIF. 2003, 174.