Improvement of Mechanical Properties of Fe-Cr-Mo-[Cu-Ni] Sintered Steels by Sinter Hardening

The effect of high temperature sintering and high cooling rate on shifting the microstructural composition to the favourably of martensite-bainite structures and thus effective improvement of mechanical properties of sintered steels based on Astaloy CrL powder with an addition of 1 and 2% Cu or 50% Distaloy AB powder and 0.65% C was investigated. All the systems were processed by both sinter-hardening and conventional sintering. The vacuum sintering at high-temperature of 1240°C and at common temperature of 1180°C were integrated with high (6°C/s), medium (3°C/s) and slow (0.1°C/s) cooling rates; conventional sintering at 1180°C with cooling rate of ∼0.17°C/s was carried out in a N2+10%H2 atmosphere. In dependence on chemical composition, the yield and tensile strengths of 890-1150 MPa and 913-1230 MPa respectively and impact energy of 10-15 J were achieved by sinter-hardening. The yield and tensile strengths are approximately double than those resulting from conventional sintering.