Sustainable micro-milling of Ti6Al4V: Role of MoS2 and CuO nanofluids in minimum quantity lubrication

Abstract

The current research explores how various nano minimum quantity lubrication (NMQL) techniques impact surface integrity in the micro-milling of Ti6Al4V. Accordingly, three combinations including MQL, NMQL + CuO, and NMQL + MoS₂ were evaluated across three different spindle speeds. Surface roughness was assessed using areal surface roughness (Sa). Findings show that increasing spindle speeds up to 32,000 rpm leads to lower Sa values across all lubrication methods. The inclusion of nanoparticles like MoS₂ enhances surface finish, with a significant reductions in Sa of 21 %. Increasing spindle speed from 16,000 to 32,000 rpm also effectively decreases burr width. Among the methods, NMQL + MoS₂ achieved the smallest burr width of approximately 110 μm. Furthermore, surface hardness increased under all test conditions, with NMQL + MoS₂ achieving the highest hardness. White layer formation is one of the challenges of micromachining. Regarding of the thickness of this layer, NMQL + MoS₂ showed the thinnest layer, and at 32,000 rpm, the white layer was completely removed. It also proves that white layer can be totally eliminated by optimizing cutting parameters under NMQL condition. Corrosion resistance evaluation revealed that NMQL + CuO had the highest resistance. Overall, the findings suggest that adding nanoparticles, particularly MoS₂, to the MQL system can significantly enhance surface properties during the micro-milling of Ti6Al4V alloy, offering a viable solution for a consistent and high-quality micro-milling process.