Novel Super-Elastic Materials for Advanced Bearing Applications

Abstract

Tribological surfaces of mechanical components encounter harsh conditions in terrestrial, marine and aerospace environments. Brinell denting, abrasive wear and fatigue often lead to life-limiting bearing and gear failures. Novel superelastic materials based upon Nickel-Titanium (NiTi) alloys are an emerging solution. NiTi alloys are intermetallic materials that possess characteristics of both metals and ceramics. NiTi alloys have intrinsically good aqueous corrosion resistance (they cannot rust), high hardness, relatively low elastic modulus, are chemically inert and readily lubricated. NiTi alloys also belong to the family of superelastics and, despite high hardness, are able to withstand large strains without suffering permanent plastic deformation. In this paper, the use of a hard, resilient NiTi alloy for corrosion-proof, shockproof bearing and gear applications is presented. Through a series of bearing and gear development projects, it is demonstrated that NiTi’s unique blend of material properties lead to significantly improved load capacity, reduced weight and intrinsic corrosion resistance not found in any other bearing materials. NiTi thus represents a new materials solution to demanding tribological applications.

Unraveling the Friction and Wear Characteristics of the High Hardness, Low Young's Modulus 60NiTi Alloy: A Synergistic FEM Simulation and Experimental Study

“…Compared to traditional bearing materials with high Young's modulus and hardness such as bearing steel, 60NiTi alloys have attracted the attention of bearing material researchers due to their equal range of hardness and excellent corrosion resistance [7][8][9][10][11][12][13][14][15][16][17][18]. The alloy has been reported to serve as a backup bearings material in the distillation centrifuges at the International Space Station [2,3,19]. However, the Young's modulus of 60NiTi alloy is about half that of bearing steel.…”

Fabrication of Ni-Rich 58NiTi and 60NiTi from Elementally Blended Ni and Ti Powders by a Laser Powder Bed Fusion Technique: Their Printing, Homogenization and Densification

“…The well-studied equiatomic or near-equiatomic shape memory NiTinol alloys are not dimensionally stable, as their austenite–martensite phase transformation temperatures are around room temperatures and show a relatively low hardness value (~30 HRC), making them unsuitable for structural applications [ 8 , 10 , 11 , 12 ]. On the contrary, the combination of dimensional stability, a high hardness that is comparable to bearing steels, and other advantageous properties of 60NiTi make this Ni-rich grade of NiTi alloys a suitable candidate for structural applications [ 8 , 13 , 14 , 15 , 16 ]. As an example, this alloy is a good candidate to be employed as a rolling element bearing material that is highly corrosion resistant and endures high levels of shock loads before experiencing any permanent deformation, and also for lubricated sliding applications [ 17 , 18 , 19 , 20 ].…”