Formation mechanism of microstructure of laser cladding high chromium Fe-based alloy and its effect on microhardness

A high chromium iron-base alloy with the coaxial powder laser coating is implemented on the surface of the 3Cr13 stainless steel blade by using 2 kW fibre-optical disc laser to improve the hardness of the blade. SEM, EDS, EPMA and XRD are used to analyze the microstructure of the cladding layer and the microhardness is tested. The results show that the cladding layer is well-formed and metallurgically bonded with the substrate without defects such as cracks, porosity and so on. With the change of the heat dissipation and the constitutional supercooling, microstructure can be roughly divided into three regions:dendritic region, eutectic fine grain region and coarse grain region. The carbides of (Fe,Cr)₇C₃ is distributed in each region to increase the hardness and abrasion resistance of the cladding layer. As the size of the grain in each region is different, the hardness of the cladding layer is differently distributed. While, the addition of Ni element promotes the austenization of the matrix in the cladding layer. It can play a role in the toughness of the carbides with high hardness during the use of the knife. Thus, the comprehensive mechanical properties of the cladding layer are obtained.