Effect of WS 2 particles in cutting fluid on tribological behaviour of Ti–6Al–4V and on its machining performance

Abstract

Tribological behaviour of Ti–6Al–4V alloy sliding against WC-Co was evaluated by employing WS₂ nanoparticles blended in a cutting fluid used for machining of this alloy. Pin-on disk tests were carried out under boundary-lubricated condition using a cutting fluid (70% water and 30% oil) blended with WS₂ nanoparticles (CF + WS₂). When a cutting fluid with ≥ 0.5 wt.% WS₂ was used, the COF of the tribosystem was reduced compared to CF + 0%WS₂. The lowest COF of 0.05 was obtained when 1.0 wt.% WS₂ was used. Low and stable COF values were accompanied by the formation of a tribolayer incorporating WS₂ and WO₃ on the WC-Co surfaces. During orthogonal machining of Ti–6Al–4V using CF + 1.0%WS₂, a tribolayer with the similar composition was formed on the cutting edge of the WC-Co tool and the average cutting force was reduced by 35% compared to cutting with CF + 0%WS₂. Machining with CF + 1.0%WS₂ produced thinner chips. Other improvements in machining performance attained using CF + 1.0%WS₂ included reduction of adhesive wear on the tool and a lower roughness of the machined surface.