Influence of laser heating on the quantity residual austenite in steels and cast irons

1. The quantity of residual austenite in the case fused under the action of a heat source (laser or plasma) on the surface of steel or iron is unambiguously determined by the parameter P/d (dv)0.4, which is proportional to the maximum temperature at the end of action of the source. 2. In 9Kh steel with an increase in the parameter P/d (dv)0.4 the quantity of residual austenite in laser fusion changes according to a curve with a maximum. In treatment with scanning of the laser beam the quantity of residual austenite in 9Kh steel continusouly increases with an increase in the parameter P/d (dv)0.4. The addition of scanning leads to an increase in the quantity of residual austenite in the case in comparison with treatment without scanning. 3. With an increase in the parameter P/d (dv)0.4 the change in the quantity of residual austenite in the zone of surface fusion of gray irons is dependent upon the degree of solution of graphite in the molten material. 4. The contact fatigue life of 9Kh steel after laser fusion of the surface is a maximum with 50–60% residual austenite in the laser hardened case. The wear resistance of gray iron after surface fusion increases with an increase in the quantity of residual asustenite in the case hardened from the liquid state.