In-situ Ti(C, N) reinforced AlCoCrFeNiSi-based high entropy alloy coating with functional gradient double-layer structure fabricated by laser cladding

• High entropy alloy gradient coating with in-situ Ti(C, N) is prepared by laser cladding. • Disordered BCC phase and ordered B2 phase constitute the matrix of second layer. • FCC solid-solution is formed in the first layer due to its high concentration of Fe. • The addition of Ti leads to high surface hardness and plastic deformation resistance. In-situ Ti(C, N) reinforced AlCoCrFeNiSi-based high entropy alloy coating with functional gradient double-layer structure is successfully fabricated on the H13 substrate using laser cladding. The microstructures and wear resistance of the gradient coating are characterized using SEM, EBSD, TEM, EDS and wear test, respectively. The results show that FCC solid-solution matrix is formed in first layer, while a mixture of disordered BCC phase (Fe-Cr) and ordered B2 phase (Al-Ni-Ti) with coherent interface is found as the matrix in second layer. Ti(C, N) ceramic particles are in-situ synthesized in the coating due to the large negative mixing enthalpy of Ti-C and Ti-N atom pairs. The solid-solution strengthening and dislocation strengthening caused by the dissolution of Ti into B2 phase, accompanying with the fine grain strengthening caused by the microstructure refinement and dispersion strengthening of Ti(C, N) particles, contribute to the high surface hardness and wear resistance. The dominant wear mechanism of this coating is oxidation wear with a small amount of abrasive wear. It can be concluded that AlCoCrFeNiSi-based high entropy alloy coating with in-situ Ti(C, N) reinforcement dramatically improves the wear resistance of the H13 substrate.