Microstructure and properties of laser-cladded bimodal composite coatings derived by composition design

The AlSiTiNi composite coatings were prepared on the surface of the 304 stainless steel by laser cladding. The results showed that a good metallurgical combination was found at the bonding area between the coating and the substrate. For the Al and Ti powders with different content, the bimodal microstructure was shown in all the coatings. However, the microstructure of the coating with a composition of 50%Al-20%Ti was more compact, and it was mainly composed of equiaxed crystal in the partially melted region and net-like structure in the fully melted region, while the partially melted region was embedded in the fully melted region. In addition, the phases of AlFe, FeNi and Al₅Cr were found in the coating. The highest micro-hardness of the coatings with the composition of 40%Al-30%Ti and 60%Al-10%Ti were 532.3 HV_0.2 and 556.8 HV_0.2, respectively. The highest micro-hardness of the coating with the composition of 50%Al-20%Ti has been increased to 758.5 HV_0.2, which was 3.4 times that of the substrate (223.2HV_0.2). Furthermore, the coating possesses low friction coefficient and high wear resistance. For the coatings with different contents, the 5A2T coating possesses the shortest the running-in period and the smallest wear loss.