Investigation into the Wear and Dent Resistance of Ni/Ti Nanolaminates and Superelastic NiTi Coating

Abstract

Metallic wear-resistant coatings, such as chromium based, are desired to prevent premature failure of working parts and are widely used in the oil and gas and aerospace industries. These coatings are extremely hard; however, researchers have found that an optimal coating will also be resilient. Bulk NiTi possesses a superelasticity effect that can provide wear resistance to parts that will experience impact, wear, and erosion daily. Yet, NiTi as a surface coating has not been fully exploited in industrial applications. Bulk NiTi production presents significant challenges, such as poor formability and machinability. This study attempts to fabricate NiTi through a heat treatment process of sputter-deposited alternating nanosized Ni and Ti layers. After annealing, the nanolaminate coatings contained the austenitic NiTi phase. The elastic modulus to hardness ratio and wear resistance showed that the nanolaminate annealed at 650 °C is comparable to the sputtered superelastic NiTi coating. The annealed nanolaminate coating is found to exhibit higher hardness than the monolayered NiTi, as well as, comparable elastic modulus to hardness values and dent resistance. The findings in this study reveal the superiority of 650 °C annealed nanolaminate NiTi coating over the monolayer NiTi.