Development of TiNbMoMnFe multi-principal element alloy coating using mechanical alloying and HVOF thermal spray

Multi-Principal Element Alloys (MPEA) were designed to possess good strength, ductility, wear and corrosion resistance, and biomedical compatibility. There are many applications where failure is associated with surface-related degradation, and suitable coatings can mitigate them. This study focuses on the development of MPEA coatings using the HVOF thermal spray process and explores their mechanical and tribological responses. In the present study, the transitional and refractory elements-based feedstocks are prepared by a mechanical alloying process using a high-energy ball mill for 5 h, 10 h, and 15 h milling time. The molar ratio of the developed coating is TiNbMoMnFeOX (1:1:1:1:1:X, where X = 0.48 to 0.62). Thus, prepared feedstock powders and coatings are characterized to record their metallurgical, mechanical, and tribological responses wherever it is applicable. The used scientific tools include X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), field emission scanning electron microscope (FESEM), universal tribometer, and nanoindenter set-up. The results show that mechanical alloying can lead to the formation of MPEA, and 15 h milled MPEA powder coating has superior performance. The process exhibited significant microstructural changes in the alloy system, and dual (TiNb and TiMo) and ternary (TiNbMo) BCC phases were developed during the process. These BCC phases are responsible for the coating's improved mechanical and tribological responses. The solid solution hardening of the ternary phase (TiNbMo) is the most dominant mechanism for improving the mechanical and tribological properties.