Surface Integrity Analysis in Orthogonal Milling of Inconel 718

Nickel-based superalloys exhibit excellent corrosion resistance and mechanical strength at elevated temperatures, making them highly sought after for safety-critical applications in the aerospace, nuclear and chemical industries. However, these advantageous properties also lead to machining challenges such as extensive tool wear and surface integrity issues. Surface integrity includes aspects such as residual stress and surface microstructure, both of which are affected by thermo-mechanical loads during the cutting process. These loads are related to variables such as cutting parameters, tool material and tool geometry, etc. Understanding the relationship between these factors and surface integrity is critical to improving the quality of the machined part. This study investigates the effects of feed rate and cutting depth on the microstructure during milling of Inconel 718 both experimentally and using simulation techniques. In the experimental phase, orthogonal milling tests were performed to measure the cutting forces and temperature distribution. The results showed that the surface deformation increased at higher feed rates but decreased at lower cutting depths. The simulations showed that thermo-mechanical loads in the workpiece rim zone are responsible for the surface deformation. The simulations indicate that the mechanical loads decrease with increasing cutting depth due to the simultaneous increase in temperature. These findings provide a theoretical basis for a better understanding of the changes in surface integrity during the machining of such superalloys.