Supersonic Laser Deposition of Composites

Abstract

Supersonic laser deposition (SLD) process as a hybrid coating technique takes the advantages of both cold spray (CS) and laser irradiation, becoming a relatively new trend in the field of coating deposition. This technique has been employed to produce diamond/Ni60 composite and WC-reinforced composite coatings. Two different sizes of diamond particles mixing with Ni60 alloy powder are deposited on medium carbon steel (AISI 1045 steel) substrate with the same optimal parameters, respectively. The diamond/Ni60 composite coatings prepared by process are studied using SEM/EDS, Raman spectra, Vickers hardness and pin-on-disc wear tests. The results show that the diamond/Ni60 composite coatings have not experienced graphitization of diamond thus exhibit better tribological properties, the smaller size of diamond is better than the larger one in the composite coatings for wear resistance. The WC/SS316L composite coatings produced by CS and SLD are compared, with respect to deposition efficiency, WC distribution and concentration, interfacial bonding, phases in the microstructures and tribological properties. The experimental results demonstrated that deposition efficiency, WC concentration and interface bonding of the composite coating can be improved by laser irradiation due to the softening of both powder particles and substrate. The SLD composite coating has the same phases as the CS coating does because of the relatively low heat involved in this process. The high concentration and strong interfacial bonding of WC particles in the SS316L matrix significantly improve the tribological properties of the SLD composite coating. Similar findings are obtained on the WC/Stellite 6 coating fabricated via SLD, compared with the laser cladding (LC) coating. The SLD WC/Stellite 6 coating appears continuous and dense without obvious defects such as pores and cracks.