Microstructure and Hardness of Laser Cladding CuNiFeTiAl High-Entropy Alloy on TC4 Titanium Alloy

Under laser power of 300‒800 W, scanning speed of 2‒6 mm·s⁻¹, and powder feeding rate of 5‒35 g·min⁻¹, CuNiFeTiAl high-entropy alloy was prepared on surface of TC4 titanium alloy plate by single-track laser cladding. The microstructure and hardness of the alloy were investigated. The results show that penetrating cracks appeared in the alloy under excessive laser power （800 W）, internal cracking and over-burning occurred at low scanning speed （2 mm·s⁻¹）, and cracks initiated within the alloy under the powder feeding rate exceeding 15 g·min⁻¹. Under a laser power of 400 W, scanning speed of 4 mm·s⁻¹, and powder feeding rate of 15 g·min⁻¹, the alloy exhibited sound metallurgical bonding with the substrate, and no cracks or pores were observed, representing the overall optimal forming quality; these parameters were identified as the optimal process. The alloy microstructure mainly consisted of equiaxed dendrites by laser cladding with the optimal process parameters. The dendritic trunks consisted of （Fe, Ni） and （Al, Ni） solid solutions, and a titanium-rich solid solution was forned in the interdendritic regions. A titanium-rich columnar crystal transition zone appeared at the coating-substrate interface. The microhardness of the alloy by laser cladding with the optimal process parameters was approximately 1.85 times that of the substrate, and the highest hardness observed in the interfacial transition zone, reaching 678.3 HV.