Abstract
Cavitation bubble activity caused by ultrasonic irradiation in water was applied to the hard surface such as carburized steel and TiN-coated on WC-super hard alloy to investigate whether it is possible or not to introduce residual compressive stress on the hard surface. The main results obtained in this study are as follows.
In the case of carburized steel with hardness of 700HV, the large residual compressive stress of approximately 820MPa was successfully introduced on the surface by the ultrasonic irradiation in water. Furthermore, it was revealed that the ultrasonic irradiation in water successfully introduced the large residual compressive stress of approximately 2400MPa on the surface of TiN-ceramic coated on WC-super hard alloy of which the initial surface residual compressive stress was about 1800MPa. The redundant application of the ultrasonic irradiation on the TiN ceramic surface after the residual stress reached the maximum caused not the variation in the surface roughness and micro-hardness but a little damage such as very small pits on the surface.
