Impact of Cryogenic Cooling on Burnishing of Ti-6AI-4V: An Optimization Approach

The present study investigates the influence of cryogenic cooling on the burnishing process of Ti-6Al-4V, a widely utilized titanium alloy in aerospace and biomedical applications. While conventional burnishing enhances surface integrity by inducing compressive residual stresses and improving hardness, excessive heat generation limits its effectiveness. Cryogenic-assisted burnishing, incorporating liquid nitrogen as a cooling medium, presents a promising alternative to mitigate thermal softening and enhance mechanical properties. This study systematically optimizes the burnishing process using the Taguchi method, evaluating the effects of key parameters like speed, feed rate, depth of cut, and number of passes on surface roughness and microhardness. Results indicate that cryogenic process significantly enhances hardness, with improvements of up to 31.5% compared to normal counterpart. However, cryogenic conditions also led to elevated surface roughness, with the maximum Ra increasing from 0.347 μm (normal) to 1.17 μm under extreme cooling (-196 °C) due to embrittlement and lower plastic deformation at ultra-low temperatures. These results highlight theºritical need for process optimization to balance mechanical enhancement with surface finish degradation. The study provides actionable insights into the cryogenic burnishing of Ti-6Al- 4V and demonstrates its potential as a superior surface modification strategy for high-performance engineering applications. Major Findings: Cryogenic burnishing of Ti-6Al-4V enhanced microhardness by 31.5% through suppressed thermal softening and improved strain hardening but increased surface roughness due to embrittlement and limited plastic deformation at ultralow temperatures. Taguchi optimization helps balance these effects, enhancing applicability in aerospace and biomedical fields.