Microstructural and mechanical study of an induction nitrided Ti gr.5 hip prosthesis component

Ti alloys suffer from intensive wear. To improve these properties, a surface treatment is required (coatings, surface thermal treatment, etc.). One of the major concerns regarding these treatments is that the treatment temperature needs to be controlled in order to avoid microstructural modifications. In this work, an attempt to modify a thin alloy surface layer alone has been performed by means of induction nitriding. By saturating the heating chamber with N, it is possible to produce controlled thickness nitride layers. Current (650–750 A) and cycle number (2–4 with a duration of 8 s each) were varied, and the top view and cross sections of the produced samples were characterized by means of stylus profilometery, SEM (Scanning Electron Microscopy) and visible light microscopy. The produced samples were then studied by microhardness and tensile testing to determine their mechanical properties. Fretting tests were also performed in order to evaluate the wearing behaviour of the surface layers in a corrosive media. The results showed that Ti alloys can be induction nitrided. The process parameters have a strong influence on the formation of TiN and alpha case layers. These layers can affect the mechanical properties and fretting resistance of the samples. [Display omitted] •The induction nitriding process has been performed on Ti gr.5 alloy.•The nitrided layer is strongly correlated with the nitriding parameters.•The nitriding process produces an external hard layer.•The induction-nitriding process decreased the ductility of the core material.•The induction-nitriding process increased the fretting resistance of the substrate.