关键词: 42CrMo钢, 激光熔覆, 同轴送粉, Fe-WC合金粉末, 显微组织, 硬度

Abstract: Fe-WC alloy powder was laser cladded on the surface of 42CrMo steel by coaxial powder feeding method. The microstructure characteristics of the clad layer, the influence of WC ceramic particles on the microstructure and properties of the clad layer, the distribution characteristics of WC particles and the composition of bulk eutectic around WC particles were observed and analyzed by scanning electron microscope, metallographic microscope and energy spectrometer. The performance and mass loss of the matrix and the clad layer were measured by microhardness tester, friction and wear tester, and high precision electronic balance, and the reasons causing the change of performance curves were analyzed. The results show that the microstructure changes from the bottom to the top of the clad layer are planar grains, cellular grains with obvious grain boundary, columnar dendrite with staggered growth, closely arranged cellular grains and columnar dendrite with uniform direction. The WC particles have the ability to refine dendrites, to block dendrite growth and to enhance the clad layer performance. The WC particles are aggregated and distributed in the clad layer to form a wider ceramic belt, and the massive eutectic around the WC particles is obtained by partial decomposition of WC, and the constituent elements of the eutectic include C, W, Fe, P and Cr. The average hardness of the clad layer reaches 850 HV0.3, which is 3.4 times of that of the matrix. The friction factor is about 0.275, which is 0.525 smaller than that of the matrix. The mass loss of the matrix is more than 11 times that of the clad layer. This shows that the Fe-WC alloy clad layer can effectively improve the hardness and wear resistance of the matrix material.

Key words: 42CrMo steel, laser cladding, coaxial powder feeding, Fe-WC alloy powder, microstructure, hardness