Enhanced mechanical properties and structural stability of Hf-modified NiTi alloy for advanced bearing materials

Ni-rich NiTi alloys suitable for bearing materials exhibit excellent properties such as high hardness, low modulus, non-magnetic, and corrosion resistance. In this study, the addition of Hf elements enhanced the mechanical properties and improved the structural stability of the alloys. The results indicate that the aging-treated Ni₅₅Ti₃₇Hf₈ alloy demonstrates outstanding properties, with a Vickers hardness of 738.7 ± 12.5 HV, a nano-hardness of 9.6 ± 0.3 GPa, and an elastic modulus of 106.1 ± 2.2 GPa. The microstructure is primarily composed of the NiTi, Ni₄Ti₃ phase, and the H-phase. The structural stability of Ni₅₅Ti₃₇Hf₈ alloy reached unprecedented levels, with hardness remaining at 673.1 ± 4.6 HV after heat treatment at 600°C for 100 h, meeting the requirements for bearing materials (exceeding 58 HRC). The Ni₅₅Ti₃₇Hf₈ alloy exhibits superior thermal stability, making it a revolutionary option for the development of next-generation wear-resistant materials.