Effect of silicon and aluminum on microstructure and properties of laser cladding MoFeCrTiW high-entropy alloy coating

In order to improve the wear resistance and high-temperature oxidation resistance of materials surface, MoFeCrTiW high-entropy alloy coating, named MoFeCrTiW HEA coating, was fabricated on Q235 steel by laser cladding. The effect of silicon and aluminum on the microstructure, phase, wear resistance and high-temperature oxidation resistance were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and wear tester. The results show that the microstructure of MoFeCrTiW HEA cladding coating is composed of equiaxed grains. After adding equimolar silicon or aluminum respectively, the microstructure of coating is eutectic or dendrites. The microstructure consists of fine equiaxed grains when adding equimolar silicon and aluminum simultaneously. The main phase of HEA coatings is BCC structure. With the addition of silicon and aluminum, the lattice constants of BCC are reduced. Adding equimolar aluminum can contribute to restrain the formation of intermetallic compound and decrease the wear resistance of coatings, whereas adding equimolar silicon can promote the formation of intermetallic compound and some unknown phases, then the wear resistance of coatings can be increased. MoFeCrTiW HEA cladding coating exhibits high oxidation resistance at 800 ℃, the high temperature oxidation of coatings can be further increased after adding silicon and aluminum.