Residual Stresses Analysis in Ball end Milling of Nickel-Based Superalloy Inconel 718

Abstract

Inconel 718 is widely used in the aviation, space, automotive and biomedical industries because of its outstanding properties. Near-surface residual stresses that are induced by ball end milling in Inconel 718 can be crucial for the performance and service time of the machined parts. In this paper, the influences of cutting conditions, including the use of cutting parameters, cutting fluid and spindle angles, on the residual stresses in the ball end milling process of Inconel 718 alloy were investigated experimentally. X-ray diffraction measurements reveal that residual stress distributions are highly influenced by cutting parameters, especially the depth of cut and cutting speed. The milling operation with cooling induces more compressive stresses trend and the magnitude of the residual stresses increases in the tensile direction with the increase of spindle angles. These cutting induced effects were further discussed with respect to thermal-mechanical coupling theory and some observations made by optical microscopy. From this investigation, it is suggested that the machining process parameters are not the smaller the better for the control of residual stresses in the ball end milling process of Inconel 718.

Surface finishing of hard-to-machine cladding alloys for highly stressed components

“…Wang et al analysed ball end milled specimens from IN718 and showed that the state of residual stresses is strongly affected by cutting conditions. The authors indicated that thermal effects due to milling process induce rather tensile stresses and mechanical effects rather compressive stresses into the component surface [28]. However, with the application of ball end milling tools, a specific optimization of the cutting process may be enabled for the most efficient utilization of the beneficial effects due to USAM process depending on the inclination or lead angle of the tool.…”

A Review on Measurement Methods for Machining Induced Residual Stress

“…He et al (He et al, 2016) evaluated the effect of cryogenic in turning Inconel 718 by measuring the distribution of residual stress across the depth of machined workpiece by using X-ray Diffraction and electro-polishing methods to remove the workpiece layer by layer. Wang et al (Wang et al, 2017) also used X-Ray Diffraction method combined with electropolishing removal process to study the near-surface and sub-surface residual stresses profile of machined Inconel 718 produced by ball end milling. Kuczmaszewski et al (Kuczmaszewski et al, 2018) have studied the state of stresses in half-finished product and in samples after machine cutting for rolled AW-2024 and AW-7075 aluminium alloys using combination of X-Ray Diffraction and electrochemical polishing.…”

“…By comparing both formations, the thermal effect has a major influence under the selected cutting conditions.The addition of coolant during milling decreases cutting temperature, improves surface quality and generates compressive stress. Wang et al (Wang et al, 2017) argued the residual stresses layer is about 80 µm below the machined surface. The tensile residual stresses magnitude increases with the increased of lead / spindle angles in the ball end milling of Inconel 718.…”

Part Functionality Alterations Induced by Changes of Surface Integrity in Metal Milling Process: A Review

“…When AISI H13 steel is hard milled by coated cutting tools, the investigated result of in-depth residual stress distribution showed that microstructural changes deeply affect the residual stress and that they have to be accurately taken into account during the process design [94]. Wang et al [95] studied the effects of cutting parameters, cutting fluid, and spindle angle on residual stress during milling of Inconel 718 alloy. The results show that the cutting depth and cutting speed have great influence on the distribution of residual stress, and the residual stress in the tensile direction increases gradually with the increase of the spindle angle.…”