Wear resistance of laser-clad Ni-Cr-B-Si alloy on aluminium alloy

Using a 5 kW CO2 laser, two kinds of plasma-sprayed coatings, Ni-Cr-B-Si an d Ni-Cr-B-Si+WC alloys, were remelted on aluminium alloy. The wear resistan ce of both laser-treated samples and plasma-sprayed samples were investigat ed using a pin-on-disc sliding friction wear tester. A scanning electron mi croscope (SEM) was used to analyse the abrasion phenomena of the samples an d a transmission electron microscope (TEM) was used to study the microstruc ture of the laser-clad zone. Experimental results showed that the laser-cla d samples had double the wear resistance of the plasma-sprayed samples, and that the laser-clad Ni-Cr-B-Si sample exhibited the highest wear resistanc e. The results of wear surface analysis showed that the microstructure of t he alloyed layer of the laser-clad samples was quite compact and the surfac es were also very smooth, and there was less peeling phenomenon of the gran ules. The microstructure of the plasma-sprayed sample was rather loose and there were a lot of granular peelings left on the worn surface. A study of the microstructure showed extensive amorphous and ultra-crystalline structu res in the laser-clad zone, to which the increase in hardness and wear resi stance may be attributed. (C) 2000 Elsevier Science S.A. All rights reserve d.