Effect of Machining Parameters on Surface Integrity in High Speed Milling of Super Alloy GH4169/Inconel 718

TLDR

Control of surface integrity is a vital consideration in the machining of components subjected to fatigue loading, for example, critical components of aerospace engines. The study analyzes how surface roughness, micro‑hardness, and residual stresses vary with cutting parameters in high‑speed milling of GH4169/Inconel 718. The authors performed finish milling of GH4169/Inconel 718 with coated cemented carbide and whisker‑reinforced coated ceramic inserts. Cutting speed, feed rate, and depth of cut all significantly influence surface integrity; the optimal combination is low feed, medium speed, and moderate depth, and carbide inserts outperform ceramic inserts, which generate high tensile stresses and poor surface finish from chip back‑striking.

Abstract

Control of surface integrity is a vital consideration in the machining of components subjected to fatigue loading, for example, critical components of aerospace engines. In this research, three important aspects of surface integrity of a machined part—surface roughness, micro-hardness, and residual stresses—were analyzed for their variations with the cutting parameters. Finish milling of super alloy GH4169/Inconel 718 was carried out using coated cemented carbide and whisker-reinforced coated ceramic inserts. All of the three machining parameters—cutting speed, feed rate, and depth of cut—were found to have a substantial effect on the surface integrity of the finished part. Although different cutting parameters gave different effects for the two types of cutting inserts, overall better surface integrity was obtained at minimum cutting feed and medium cutting speed and depth of cut value. Moreover, carbide inserts produced better surface integrity of the finished part, whereas ceramic inserts generated very high surface tensile stresses and poor surface finish due to back striking of the adhered metal chips.