چكيده به لاتين
Surface compositing with laser beams is one of the methods used to improve the abrasion resistance of tool steels. In this research, composite coatings were fabricated by preplacing a TiC layer on H13 tool steel and surface melting with a pulsed Nd: YAG laser. The effect of pulsed laser variables, TiC layer thickness, and the size of TiC powder particles on the dissolution of TiC particles in the molten pool, the formation mechanism of hard phases during solidification, and the size and morphology of these precipitates were investigated. The results showed that less effective peak power density, thicker TiC preplaced layer, and smaller particle size of TiC powder could result in a higher concentration of dissolved titanium and carbon in the molten pool. In cases where the concentration of (Ti, M) C carbides in the composite is less than 15% by weight, their shape is a delicate petal consisting of polygons that are connected or individual and have a size of fewer than 2 micrometers. If the concentration of (Ti, M) C carbides in the composite is more than 18% by weight, they are often distributed in a dendritic form with a size greater than 5 micrometers. Due to the high cooling rate of the molten pool, its variation as a result of changes in laser variables are not large enough to affect the growth mechanism of (Ti, M) C carbides. However, due to changes in the chemical composition of the molten pool, the solidification range of (Ti, M) C carbides also changes, which can determine their final morphology. As the size of (Ti, M) C precipitates increases, the maximum microhardness of the composite coating increases. The average microhardness of a composite with 15% by weight (Ti, M) C reaches about 1300 HV0.2, which is more than twice the base steel microhardness.
