EVOLUTION OF MICROSTRUCTURE AND EMBRITTLEMENT DURING THE TEMPERING PROCESS IN SiCrCu MEDIUM-CARBON STEELS

The effect of Cu and Si contents on the evolution of embrittlement during a heat treatment consisting of quenching into an oil bath and tempering in the range 200–500 °C was investigated in medium-carbon steels with 0.48 w/% and 0.57 w/% of C. The results showed that the higher silicon content shifted the tempered martensite embrittlement to higher tempering temperatures. The steels alloyed with Cu had lower notch-toughness values, which worsened with increasing tempering temperature compared to the Cu-free samples. In the investigated tempering temperature range, the following microstructural changes occurred: formation of transition carbides, decomposition of retained austenite, and precipitation of cementite and Cu-particles.