Microstructure and mechanical properties of composite strengthened high-chromium cast iron by laser quenching and laser shock peening

Abstract

The study investigated the microstructure and mechanical properties of composite strengthened high-chromium cast iron by laser quenching and laser shock peening. Observation of microstructure, measurement of microhardness, residual stress and FWHM (full width at half maximum), impact toughness and wear tests were carried out on untreated, laser quenched, laser quench-laser shock peened high-chromium cast iron specimens. The research results showed that the laser shock peening will not produce new phases in high-chromium cast iron, and can further promote the transformation of retained austenite into martensite. The grains inside the laser quench-laser shock peened sample were obviously refined, and the carbides were uniformly dispersed. The laser quench-laser shock peened specimen produced large residual compressive stress and FWHM value on the surface, reaching −432.49 MPa and 2.124°, respectively. The problem of residual stress difference between the hardened zone and the transition zone caused by laser quenching was eliminated, and the tensile stress was all converted into compressive stress, which further increases the dislocation density and improves the micro-hardness. The impact toughness value of laser quench-laser shock peened specimen was 4.43 J/cm2, which was 16.27% higher than that of the untreated sample. The friction coefficient and wear rate were significantly reduced, and the wear scar was shallow and narrow, showing weak abrasive wear and oxidative wear, the impact toughness and wear resistance of high-chromium cast iron were improved. The results obtained from this study could be used as reference in future research and applications of laser strengthened high-chromium cast iron.

Keywords

• High-chromium cast iron
• Laser quenching
• Laser shock peening
• Microstructure
• Impact toughness
• Wear performance