Synthesis and characterization of refractory TiZrNbWMo high-entropy alloy coating by laser cladding

A novel refractory high-entropy alloy (HEA) coating with composition close to TiZrNbWMo was synthesized on 45 # steel by laser cladding. Constituent phases, microstructure, chemical composition and microhardness of the coatings before and after annealing were investigated by XRD, SEM, TEM, EDS and micro/Vickers hardness test, respectively. Results showed that the TiZrNbWMo coating was similar to 513 mu m in thickness. The microstructure of the coatings exhibited typical dendritic and interdendritic structure. The coating was composed of a major body-centered cubic (BCC) solid solution and a small amount of (beta-TixW1-x precipitated phase due to high-entropy affect and laser rapid solidification. Apart from enhanced fraction of beta-TixW1-x precipitation, the struc-ture and BCC solid solution phases remained almost unchanged after annealing at 800 degrees C, 1000 degrees C, and 1200 degrees C for 20 h, indicating that the coating had high thermal stability. The microhardness of as-clad HEA coating reached around 700 HV0.5, which was three times of 45 # steel substrate. The coating microhardness increased signifi-cantly after annealing, which was due to the solid solution strengthening of BCC matrix and formation of beta-TixW1-x precipitation. Notably, the highest value was up to 1300 HV0.5 after heat treatment at 800 degrees C. Therefore, the HEA coatings showed high microhardness and resistance to softening. (C) 2017 Elsevier B.V. All rights reserved.