Evolution of surface integrity and tribological characteristics of Incoloy 925 under sequential multi-pass end...

Multi-pass machining processes are essential to get the specified shape and dimensions of the product. The thermal softening and work hardening histories from prior cutting passes can substantially influence the performance of subsequent cutting passes. This research has two investigative stages. The initial phase of the investigation examined the sequential cutting strategies and the impact of multi-pass end milling of Incoloy 925 on cutting force, chip morphology, and surface integrity, specifically regarding surface roughness, micro-morphology/surface topography, micro-hardness, microstructure, and crystallographic texture of the machined surface layer. The third cutting pass shows the highest cutting force, being 32.48% and 12.28% greater than the first and second passes, respectively. The surface roughness in the third pass is also increased, measuring 36.6% and 12.81% higher than that of the first and second passes, respectively. Similarly, the micro-hardness observed in the third pass, across all depths from the machined surface, exceeds that of the earlier passes. These results clearly demonstrate the influence of preceding passes on the performance and outcomes of subsequent machining operations. Further, EBSD analysis indicates that the extent of grain refinement and the evolution of crystallographic texture in the machined layer have intensified with an increasing number of cutting passes. XRD examination, however, reveals the absence of phase transition in all cutting passes. The second part of the study examined the impact of thermo-mechanical loading history on the tribological behavior of machined components subjected to multi-pass cutting. The samples subject to the initial cutting passes have been found superior to subsequent passes in terms of tribological performance.