Formation of Coatings by a Method of Overlay Laser Welding of Powders of Titanium and Silicon Carbide on a Surface of Low-Carbon Steel

Possibility of fabrication of the reinforcing particles of finely divided titanium carbide (TiC) evenly spread across the coating directly in the course of weld deposition is considered. Powders of titanium (Ti) and silicon carbide (SiC) are used in the experiment. Average dimension of powder particles is 50 micrometres. According to the target goals, the following parameters of weld deposition are chosen: laser power of 3-5 kWt, laser beam scanning rate from 500 to 1000 mm/min, mass powder flow rate of 9.6, 11.9, and 21.0 g/min. In the course of experiment, optimal parameters of weld padding are determined as following factors of quality of deposited coatings: the absence of pores and cracks in deposited layers, magnitudes of microhardness, and geometrical dimensions of coatings. Studies of microstructure, phase compositions, and microhardness of deposited coatings are carried out. To study working properties, testing for fretting wear of deposited layers is performed. As the result of performed investigations, optimum modes of laser weld deposition are determined. Under these conditions, TiC evenly spread across the coating is formed as the result of reaction between Ti and SiC. Average magnitudes of microhardness of the weld deposited matrix are 700-800 HV. For areas with high numbers of carbide inclusions, magnitudes of microhardness are 1300-1500 HIT and 1000-1300 HV for 6:5 and 6:4 ratios of initial-mixture components, respectively. Possibility of fabrication of hard and wear resistant coating from Ti and SIC powders, using laser weld deposition, is shown.