Laser-induced Surface Modification of a Cu-based Powder Metallurgy Friction Material
Y. Shi, H. Zhang and S.Y. Liu
A Cu-based powder metallurgy friction material was modified by CO2 laser radiation to improve its combination properties. The microstructures were characterized by means of X-ray diffraction (XRD), electro-probe microanalyser, a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The properties were characterized using a microhardness tester, a Brinell hardness tester and a wear tester. It was found that the material with and without laser treatment was mainly composed of α-Cu and graphite. But after the laser surface modification the grain size of the Cu had decreased by 35%, the average square root value of second strain was increased by 39% and the apparent value of dislocation density was increased by 97%. The α-Cu was refined to form a amorphousnanocrystal microstructure. The microhardness of the α-Cu was increased by 14%. The apparent hardness of the laser treated material was increased 12.7%, while the wear resistance was increased by 45% and the friction coefficient was increased by 1% as compared with the untreated material.
Keywords: Laser surface modification, powder metallurgy friction material, Cu-based, amorphous, nanocrystal, friction, wear