Surface modification and effects on tribology by laser texturing in AlO.

We investigate the surface modification by laser texturing and effects thereof on the tribological performance in . By detailed observation for microstructure evolution, it has been shown that there were three distinct modification morphologies by laser treatment: dense surface microfeatures, "coral" dendritic structures, and coarse grains. X-ray diffraction (XRD) results indicated that there was no formation of metastable phases due to low supercooling in solidification in the nanosecond laser regime. The formation of AlN compounds in the laser-treated region was examined by using x-ray photoelectron spectroscopy (XPS), which led to dense surface microfeatures and randomly distributed pores formation in the laser treated region. The formation of "coral" dendritic structures on the edge of groove and coarse grains in the vicinity of the laser surface was attributed to the fast-cooling rates. Wear tests were carried out to analyze the effect of laser texturing on tribological performance. The results of coefficients of friction (COF) illustrated that laser texturing can significantly improve COFs for dry friction; however, it decreases the COFs for wet friction. The mechanism of wear was explained based on a SEM measurement for worn surfaces; the formation of surface texture can store abrasive particles and debris lead to hydrodynamic lubricant film formation and the COFs significantly reducing for wet friction.