Effect of Annealing on the Impact Resistance and Fracture Mechanism of PNC-60 Sinters After Cold Plastic Deformation
Tóm tắt
Compaction of sintered metal powders by free upsetting at room temperature dangerously reduces their plastic properties, particularly the fracture toughness. The reason for the occurrence of two unfavorable phenomena accompanying this deformation route is sought. The first phenomenon depends on the initial porosity of the preform and the amount of cold work resulting in the destruction of bonds and violation of continuity between sintered powder particles. The second phenomenon is the deformation of the metal matrix, which reduces the plasticity of the sintered product. To correctly assess the effect of changes occurring in the matrix as a result of deformation, it is necessary to use the properly defined sintered matrix hardening parameter discussed in this study. The adverse effects of cold forming can be eliminated by annealing the deformed sinters at a temperature below the sintering point and above the recrystallization temperature. The annealing temperature causes favorable changes in the structure and increases the impact resistance of the deformed sinters depending on the degree of deformation of the sintered matrix and the initial porosity of the preform. Annealing at a properly selected temperature restores the ductility of the metal matrix and improves the integrity of the sintered material impaired by the effect of deformation. Annealing also causes favorable changes in the porosity morphology, removing defects in the form of gaps and resulting in the spheroidization of voids. With an appropriately selected initial porosity and degree of deformation, subsequent annealing of sinters compacted by free cold upsetting provides products with strength properties comparable to sinters with the same density and subjected to single compaction and sintering but with considerably higher fracture toughness.
Tài liệu tham khảo
R.M. German, Powder Metallurgy and Particulate Materials Processing, Metal Powder Industries Federation, New Jersey, 2005, p 528
T. Takemasu, T. Koide, T. Shinbutsu, H. Sasaki, Y. Takeda, and S. Nishida, Effect of Surface Rolling on Load Bearing Capacity of Pre-alloyed Sintered Steel Gears with Different Densities, Procedia Eng., 2014, 81, p 334–339. https://doi.org/10.1016/j.proeng.2014.10.002
S. Narayan, A. Rajeshkannan, K.S. Pandey, and S. Shanmugam, Workability Behaviour of Fe-C-Mo Steel Preforms During Cold Forging, J. Iron. Steel Res. Int., 2013, 20(9), p 126–130. https://doi.org/10.1016/S1006-706X(13)60167-3
S. Narayan and A. Rajeshkannan, Workability Studies in Forming of Sintered Fe-0.35C Powder Metallurgy Preform During Cold Upsetting, J. Iron. Steel Res. Int., 2011, 18(12), p 71–78. https://doi.org/10.1016/S1006-706X(12)60012-0
Y. Kamakoshi, I. Shohji, Y. Inoue, and S. Fukuda, Improvement of Mechanical Strength of Sintered Mo Alloyed Steel by Optimization of Sintering and Cold-Forging Processes with Densification, IOP Conf. Ser. Mater. Sci. Eng., 2017, 257, p 012011. https://doi.org/10.1088/1757-899x/257/1/012011
J. Nowacki, Spiekane metale i kompozyty z osnową metaliczną, WNT, Warszawa, 2005
W. James, R. Causton, and J. Fulmer, US Patent, 5080712: Optimized Double Press-Double Sinter Powder Metallurgy Method (1992)
A. Khodaee, M. Vattur Sundaram, M. Andersson, A. Melander, A. Strondl, I. Heikkilä, A. Miedzinski, L. Nyborg, and M. Ahlfors, Innovative Powder Based Manufacturing of High Performance Gears, in Proceedings of World PM 2016, Hamburg, Germany (2016)
G. Hammes, R. Schroeder, C. Binder, A.N. Klein, and J.D.B. de Mello, Effect of Double Pressing/Double Sintering on the Sliding Wear of Self-Lubricating Sintered Composites, Tribol. Int., 2014, 70, p 119–127. https://doi.org/10.1016/j.triboint.2013.09.016
C. Recknagel, A. Marquardt, I. Langer, S. Müller, and B. Kieback, Powder Pressing: Higher Densities of PM-Steels by Warm Secondary Compaction and Sizing, in European Congress and Exhibition on Powder Metallurgy European PM Conference Proceedings (The European Powder Metallurgy Association, 2011), p. 1
A. Kosoń-Schab, Własności Mechaniczne Odkształconych Plastycznie Spieków Metali. Dissertation, Politechnika Krakowska, Kraków (2005)
K. Zarebski, S. Okonski, P. Putyra, and A. Tabor, Plastic Properties of Cold-Deformed Iron-Based Sintered Materials, Arch. Foundry Eng., 2010, 10(3), p 57–60
E. Dudrová and M. Kabátová, Fractography of Sintered Iron and Steels, Powder Metall. Prog., 2008, 8(2), p 59–75
E. Dudrová and M. Kabátová, A Review of Failure of Sintered Steels: Fractography of Static and Dynamic Crack Nucleation, Coalescence, Growth and Propagation, Powder Metall., 2016, 59(2), p 148–167. https://doi.org/10.1080/00325899.2016.1145786
P. Kulecki, E. Lichańska, A. Radziszewska, and M. Sułowski, Fractography and Porosity Analysis of Cr and Cr-Mo PM Steels, Arch. Metall. Mater., 2016, 61(3), p 1613–1622. https://doi.org/10.1515/amm-2016-0263
S. Okonski, Podstawy plastycznego kształtowania materiałów spiekanych z proszków metali, Monografia 153, Politechnika Krakowska, Kraków, 1993
H. Kielkucki, S. Okonski, and Z. Polanski, Charakterystyki materiałowe kształtowanych plastycznie spieków metali., Projekt KBN nr 7 T 08 D 00910/1996 (1996)