The water droplet erosion resistance of Ni-based composite coating through laser cladding

Abstract

Water droplet erosion (WDE) usually occurs in TC4 turbine blades under actual working conditions, which seriously endangers the safe and stable operation of the turbine. To solve the problem of WDE in TC4 turbine blades under high-speed solid-liquid impact, CeO2/Ni60A composite coatings with different laser powers were successfully developed on the surface of TC4 by using laser cladding technology. The working environment of the turbine blade under high- speed solid-liquid impact was simulated by water jet technique, and the effect of laser power on the coating resistance to water droplet erosion was analyzed. It can be seen from the results that the coating was composed of α-Ti, Ti2Ni, TiB2 and TiC, and laser power had a significant influence on the growth of grain structure. At 6000 W laser power, the average microhardness of the coating reached 1105 HV0.3, i.e., 3.25 times of TC4 substrate. However, too high laser power made the hard phases of TiC and TiB2 brittle. In the water droplet erosion experiment, the high power resulted in the cracks in the coating. At the laser power of 5000 W, the grain refinement effect was the best. The width and depth of water erosion were 0.908 mm and 0.148 mm, respectively, which were lower than TC4 substrate by 27.5% and 41.5% times. The preparation of CeO2/Ni60A coatings on the surface of TC4 alloy was effective to solve the problem of WDE in TC4 turbine blades and prolong the service life of TC4 blades. Moreover, the finer the grain structure in the coating, the better the WDE resistance.