Investigations on the adhesion and fatigue characteristics of hybrid surface-treated titanium alloy

This study is critical for aiding the development of a hybrid treatment consisting of a tungsten-doped diamond-like carbon coating (WC/C) deposited atop shot-peened Ti-6Al-4V surfaces. Residual stresses, considered a key indicator of fatigue performance, were measured by X-ray diffraction (XRD). Rotating bending fatigue tests were carried out while microscopy allowed for fractographic analysis of resultant surfaces. Results show that despite the pronounced surface roughness produced by the shot peening treatment, the high residual compressive stresses, together with the refined and cold-worked microstructure were capable of marginally improving the fatigue performance of the shot peened Ti-6Al-4V compared to the untreated alloy. Conversely, following fatigue testing, the WC/C coating displayed extensive cracking which propagated prematurely into the substrate and yielded a reduction in fatigue limit. On the other hand, despite some annealing of the compressive residual stresses during the coating deposition treatment, the hybrid treatment yielded a reasonable improvement in the fatigue limit over the untreated condition. This result, coupled with the high coating hardness and adhesion, confirm this hybrid treatment's capability in retaining both the adhesive and fatigue performance of the Ti-6Al-4V alloy. •Hybrid surface modification to enhance the surfaces conitions of Ti alloy•Enhancement of adhesion and fatigue properties due to high compressive stresses•Hybrid surface treatment has significantly improved the surface integrity.•Stiffness of WC/C coating resulted in marginal detriment to the fatigue properties.