The microstructure and tribological characteristics of laser-clad Ni-Cr-Alcoatings on aluminium alloy

Using a 5-kW CO2 laser, a Ni-Cr-Al plasma coating on Al-Si alloy surface wa s remelted. The microstructure of the clad zone was analysed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It w as found that some amorphous structures and crystallites exist in the laser -clad Ni-Cr-Al coating. The annealing treatment was used at 520 degrees C i n different time intervals in order to determine the content of amorphous s tructure in the coating. Wear tests of laser-clad samples paired with grey cast iron were carried out on a block-on-ring wear tester under oil lubrica ted conditions. The effect of amorphous structure on tribological character istics of the pairs was investigated. The result showed that the wear amoun t of laser-clad samples was quite small. The higher the amorphous content, the smaller the wear amount of laser-clad samples and grey cast iron. The a morphous structure can prevent hard granules spalling from the matrix durin g the wear test and can improve wear resistance. (C) 2000 Elsevier Science S.A. All rights reserved.