An Investigation Of Cracking In Laser Cladding For High-Speed Wire Roller

Cobalt-based alloy is widely used in plasma spraying, flame spraying for its high temperature strength and good wearing resistance.Laser cladding is a kind of surface treatment technology with good prospect. Compared with traditional surface technologies (plasma spraying, bead weld, etc.), it has low heat input, deformation and rate of dilution. Because laser clad is metallurgy bonded with substrate, with fine crystal grain and super performance of wearing resistance and corrosion resistance, it is better than the traditional one. In the high-speed wire roller production, laser cladding technology can save a large amount of valuable metals and simplify the working processes compared with powder sintering roller. It has a great social significance. Clad cracking is the key for the laser cladding of high-speed wire roller. In this paper, cracking in CO2 and YAG laser cladding of cobalt-based alloy for high-speed wire roller is studied. The main results are as followings.Processing parameters have significant effect on the cracking susceptibility of Co-base alloy. Cracking rate is decreased by increasing the laser power or reducing the feed rate. The cracking rate of clad is increased as the scan speed increasing in CO2 laser cladding, on the contrary, it is decreased in YAG laser cladding. In general, YAG laser cladding has higher crack tendency than CO2 laser cladding. It is because the wave length of YAG laser is shorter than CO2 laser's, and the absorption coefficient of YAG laser for powder is higher than CO2 laser's . The height-to-width ratio of YAG laser clads is higher than CO2 laser's. Wide-band laser cladding with strip integral mirror can reduce the crack tendency, because strip integral mirror can change laser beam form from circular to rectangular, and make laser energy distribution uniform resulting in the uniformity of clads stress. A new method for estimating...