Variation of Microstructure and Mechanical Properties of Nbmovcr High-Entropy Alloy Coatings Doped Silicon

Abstract

NbMoVCrSix high-entropy alloy coatings with different Si contents were prepared via magnetron sputtering technology. The evolution in microstructure, hardness, toughness, coating/substrate bonding strengthen, and wear behavior of the coatings was investigated comprehensively to explore the effect of Si element. The results showed that the coating structure transformed from the body-centered cubic phase to fully amorphous structure owing to the enhanced lattice distortion and negative mixing enthalpy caused by the introduction of Si. With the trace Si doping, the hardness of the coating improved significantly, which was dominated by the effects of fine grain strengthening and solid solution strengthening. Meanwhile, the average friction coefficient and wear rate of the coating were all decreased remarkably due to the improved hardness and toughness, and the formation of lubricating tribo-oxide layer containing SiO2. However, when Si doping was excessive, the comprehensive properties of the coating deteriorated seriously due to the reduced hardness and limited deformation ability of the amorphous materials.

Keywords: High-entropy alloy coating, Si doping, Wear resistance, Strengthening mechanism