Synthesis of equi-atomic Ti-Al-Mo-Si-Ni high entropy alloy via spark plasma sintering technique: Evolution of microstructure, wear, corrosion and oxidation behaviour

Equi-atomic Ti-Al-Mo-Si-Ni high entropy alloys (HEAs) with outstanding wear and oxidation properties is fabricated by means of Spark plasma sintering (SPS) technology. The influence of sintering temperature on surface microstructure, phase evolution, densification, microhardness, corrosion, wear and oxidation properties of developed Ti-Al-Mo-Si-Ni HEAs was investigated at 800 °C, 900 °C and 1000 °C. The microstructural evolutions of the synthesized HEAs were evaluated by means of scanning electron microscope coupled with energy dispersive spectroscopy (SEM/EDS). The SEM images showed no significant major porosity; however for the HEA sintered at 800 °C, the densification results prove that 2.6% porosity is present in the HEAs. XRD showed the presence of BCC and FCC solid solution structures with intermetallic precipitates of TiSi2 and Ni2Si2. The Vickers microhardness and wear resistant properties was evaluated using diamond base micro hardness tester (EMCO) and tribometer (Rtec) respectively, with the sample sintered at 1000 °C showing maximum densification of 98.8% with microhardness of 612HV and coefficient of friction (CoF) of 0.23µ. The developed HEAs also showed good oxidation resistant behaviour after a test using thermal gravimetric analyzer (TGA).