Atmospheric Influence on the Structural and Mechanical Properties of TiN Coating Deposited on NiTi Shape Memory Alloy via Mather-Type Dense Plasma Focus

Introduction and Objectives: Nickel-titanium alloys have poor hardness and tribological properties. There is a possibility of loosening caused by wear while using these alloys for medical applications such as artificial bone joints. The hardness, wear resistance, and corrosion resistance of the surfaces can be improved by deposition of coatings such as TiN. The study's main objective was to investigate how the deposition atmosphere affects the morphological and microstructural properties and the mechanical and corrosion behavior of the coatings.Materials and Methods: This study demonstrates the effective use of the dense plasma focus method to deposit titanium nitride coatings onto nickel-titanium shape memory alloys in various atmospheric conditions. The atmospheres used were (i) 50 vol. % argon and 50 vol. % nitrogen, and (ii) 75 vol. % argon and 25 vol. % nitrogen.Results: Nitriding process under the above-mentioned conditions increased the hardness of the samples. The average hardness of samples 0.5N2-7 and 0.25N2-7 were obtained to be ~ 459 HV and 410.5 HV, respectively. At a constant distance from the anode to the sample surface, with a decrease in the ratio of nitrogen to the total inlet gas, the sputtering rate in the chamber increases and leads to an increase in the coating thickness. The coating thickness of samples 0.5N2-7 and 0.25N2-7 were obtained to be 0.91 µm and 1.75 µm, respectively.Conclusion: Scanning electron microscope images of the coating surfaces indicated that the nitriding process in the 75 vol. % argon and 25 vol. % nitrogen environment was more effective in preventing cracking. Additionally, lowering the nitrogen ratio in the atmosphere led to a higher sputtering rate within the chamber, contributing to an increase in coating thickness and improved corrosion resistance.