The effect of pre-deposited titanium-based PVD metallic thin films on the nitrogen diffusion efficiency and wear behaviour of nitrided Ti alloys

• Published in: Surface & coatings technology Vol. 394; p. 125545
• Main Authors: Yumusak, G., Leyland, A., Matthews, A.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 25.07.2020; Elsevier BV
• Subjects: Bearing capacity; Diffusion coating; Diffusion coatings; Fatigue strength; Ion nitriding; Low temperature; Magnetron sputtering; Micro-abrasion test; Niobium; Plasma diffusion; Pretreatment; Substrates; Thin films; Titanium alloys; Titanium base alloys; Titanium-niobium coatings; Triode plasma nitriding; Wear; Triode plasma nitriding; Magnetron sputtering; Micro-abrasion test; Titanium-niobium coatings
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2020.125545

Low-temperature Triode Plasma Nitriding (TPN) has been reported to increase the load-bearing capacity of titanium alloys without compromising either core strength or fatigue resistance. It is known also that the effective adhesion between PVD hard coatings and titanium alloy substrates can be improved significantly following substrate diffusion pre-treatment. In TPN treatment the diffusion of the nitrogen can be achieved more efficiently (than conventional nitriding techniques) at a comparatively low substrate temperature and after relatively short treatment times. Moreover, there is evidence to suggest that the effectiveness of the triode-plasma diffusion treatment can be further increased by depositing a suitable thin PVD metallic layer on to the titanium alloy substrate before plasma nitriding treatment, to beneficially modify the diffusion kinetics. In this paper, both hcp-α and bcc-β titanium coatings (the latter stabilised by the addition of Nb) are applied to (α + β) Ti-6Al-4V and (β) Ti-4Al-10V-22Mo substrate materials; the effects of α Ti and β Ti-Nb PVD pre-coating on the diffusion treatment efficiency (and nitride phase development) and the wear behaviour of each of the Ti alloy substrates after TPN treatment at 700 °C is evaluated. •To obtain fully β-phase of Ti-Nb coatings, it is selected at around 33 at. % Nb.•The hardening effect for Ti-Nb coated Ti-64 substrate was found to be higher.•The hardening effect for Ti coated Ti-AVM substrate was found to be higher.•The 1.25 μm thick surface coatings were sputtered off completely after 4 h nitriding.•The Ti and Ti-Nb surface coatings provided a noticeable benefit in abrasion.