Microstructure and corrosion property of TC4 coating with Al0.5CoCrFeNi high-entropy alloy interlayer by laser cladding

In this work, TC4 coating was prepared on 45 steel surface successfully by laser cladding and Al0.5CoCrFeNi high-entropy alloys (HEA) coating was designed as an intermediate layer. Microstructure, microhardness and electrochemical corrosion characteristics of TC4/HEA composite coating were evaluated in detail. The interfaces without cracks of HEA layer/substrate and TC4 layer/HEA layer are clear and straight, and a metallurgical bonding is obtained when the line energy density is 315 J/mm2 and 180 J/mm2. A reactive layer consisted of TiAl and TiFe intermetallic compounds (IMC) is formed at TC4/HEA interface. The HEA transition layers are composed of uniformly distributed equiaxed matrix (FCC) and intercrystalline phase (BCC), while a transition from Widmanstätten structure to coarse acicular crystal was found in TC4 layer. The microhardness of HEA coating is slightly higher than the substrate and lower than the TC4 coating, and the microhardness value of TC4 layer is up to 745.8 HV0.2. Potential dynamic polarization curves test results show that a comparatively small corrosion zone is concluded for TC4/HEA composite coating sample and the corrosion resistance of the composite coating is significantly improved with an increased value of 55.9 % in Ecorr (−0.325 V) and a decreased value of 99.3 % in Icorr (0.1 μA/cm2) compared to the substrate.