DRY SLIDING WEAR BEHAVIOR OF A P/M FERROUS ALLOY SUPERFICIALLY DENSIFIED BY LASER SHOCK PROCESSING

A potentially promising application of laser shock processing is in the superficial densification of porous materials. The present work studies the effect of laser shock processing on the dry sliding wear behaviour of powder metallurgical (P/M) Distaloy AE specimens of four different porosity levels in the range 9-22 vol.%. The wear mode for laser-shocked specimens compared with that of the corresponding unshocked specimens was investigated using a pin-on-disc apparatus and a 99% pure sintered alumina counterbody. Densification was characterized using quantitative image analysis since shock treatment resulted in a porosity gradient in the processed depth. The basic mechanisms involved in the wear of the specimens were shown to be oxidation, abrasion and plastic deformation leading to metallic particle detachment. Laser shock densification increased the wear resistance of the specimens with initial porosity lower than 10 vol.%. In contrast, the wear resistance of the specimens with high initial porosity(16.8 and 21.1 vol.%) and large initial pore size (greater than 20 mu m) was shown to decrease after laser shock, since the beneficial mechanism of debris entrapping by the pores and pore filling could not take place.