Comparison of Heat Treatments on the Toughness of 1.7Ni-1.5Cu-0.5Mo Pre-alloyed P/M Steels

摘要

Effects of quenching plus tempering and intercritical annealing plus quenching heat treatments on the impact toughness properties of 1.7Ni-1.5Cu-0.5Mo pre-alloyed powder metallurgy steels with 0.2 ( in mass) graphite were investigated. Specimens were prepared by pressing at 670 MPa and sintering at 1250 degrees C. Different heat treatments, namely quenching and tempering, directly intercritically annealing and fully austenization plus intercritically annealing were carried out on the -sintered specimens. The results showed that the impact toughness decreased with increasing intercritical annealing temperature in ferrite plus martensite dual phase powder metallurgy steels and with increasing tempering temperature in the quenched plus tempered specimens. Besides, impact toughness of fully austenizated plus intercritically annealed specimens was higher than those of quenched plus tempered and directly intercritically annealed specimens at the same hardness levels.