Effect of quench-tempering and laser quenching on the microstructure and properties of high-chromium cast iron

Abstract

In this paper, quench-tempering (QT) and laser quenching (LQ) treatments were performed on the high-chromium cast iron to obtain better microstructure and mechanical properties. The changes in microhardness, microstructure, retained austenite (RA) content, grain size, phase and elemental content of the QT and LQ samples were compared and analyzed. The results showed that the RA content of the untreated samples was 77.02% and the was 26.8 nm. The QT samples showed an increase in carbide dissolution, gradual rounding from sharp angles, transformation of austenite into martensite, reduction of RA content to 28.48%, average grain size (AGS) of 35.8 nm, increase in surface microhardness by 16.6%, and the friction coefficient was reduced by 6.9%. The LQ samples showed a large amount of fine martensite, daisy-like eutectic carbides and diffusely distributed secondary carbides, and the RA content was reduced to 17.72%, with an AGS of 29.9 nm. Compared with the QT samples, the LQ samples showed a 25.1% reduction in AGS, a 16.5% increase in surface microhardness, and a 9.7% decrease in friction coefficient, which was more wear resistant. However, the hard and brittle surface layer of the LQ samples tended to be a source of cracks during impact, resulting in a final reduction of 8.4% in impact toughness compared to the QT samples.