Improvement of Strength Properties of Fe-Cr-Mo-Cu-Ni-C Sintered Steels by Sinter-Hardening

摘要

The effect of high temperature sintering and high cooling rate on shifting the microstructure composition to favourably portion of high strength structures and thus strength properties improvement of the Fe-Cr-Mo-[Cu-Ni]-C sintered steels based on Astaloy CrL was investigated. All the systems were processed by both sinter-hardening and conventional sintering. The high temperature vacuum sintering (1180°C) was integrated with high (6K/s), medium (3K/s) and slow (0.1K/s) cooling rates; the conventional sintering at 1180°C with the cooling rate of ~0.17K/s was carried out in N_2-rich atmosphere. Depending on chemical composition, the yield and tensile strengths of 890-1150 MPa and 913 -1230 MPa were achieved by the applied sinter-hardening. All the values are approximately double than those for pearlite/bainite structures after conventional sintering. Finally, basing on the microstructure composition and corresponding microhardness, the (theoretical) tensile strength of the "pore free" matrix was calculated. The difference between calculated and experimental tensile strength values was explained by microfractographic observations.