Characterisation of Deformation Microstructure Beneath Machined Surface and Its Role in the Dimensional Stability of Alloy 718

Identification of Subsurface Deformation in Machining of Inconel 718

“…In addition, higher machining speed results in a deeper deformation layer under dry machining conditions and at the same cutting speed, dry machining produced deeper deformation layer than lubricated machining. To further understand the microstructure of Inconel 718 at near surface, recently, transmission electron microscopy was used in the several investigations [2].…”

“…Depending upon their nature, the characteristics of subsurface can have significant effects on component life by influencing fatigue, creep, and stress corrosion cracking resistance. Sometimes, improper selection of machining parameters would induce unexpected subsurface properties which would lead to the large initial wear of machined surface [1,2]. Thus there is considerable industrial significance to understand the nature of plastic deformation under the machined surface for correctly prediction of formation of subsurface properties based upon the machined conditions and material behaviours that give rise to them.…”

Influence of surface modifications on pitting corrosion behavior of nickel-base alloy 718. Part 1: Effect of machine hammer peening

“…It is known that the SFE of nickel-base alloy 718 is of an intermediate value, and it has been shown in some publications that twinning dominated the deformation process in alloy 718 under different mechanical treatments [51,53]. Sundararaman et al [51] have investigated the deformation microstructure beneath the machined surface of alloy 718 and they have noticed that two distinct subsurface layers were formed, one in which grains were heavily fragmented and the other below this layer where grains still maintained their identity through heavy deformation had occurred within them. They proposed that the predominant mode of deformation in the heavily fragmented zones on the machined surface of alloy 718 appeared to be multiple twins with very fine size, and it changed to elongated twins to slip because the plastic strain sharply decreased with increase in depth from the machine surface.…”

“…In general, slipping is the predominant mode of deformation for materials those have medium to high stacking fault energy (SFE), while twinning is very popular in lower SFE materials, especially at high strain rates or very large strains [50][51][52]. It is known that the SFE of nickel-base alloy 718 is of an intermediate value, and it has been shown in some publications that twinning dominated the deformation process in alloy 718 under different mechanical treatments [51,53]. Sundararaman et al [51] have investigated the deformation microstructure beneath the machined surface of alloy 718 and they have noticed that two distinct subsurface layers were formed, one in which grains were heavily fragmented and the other below this layer where grains still maintained their identity through heavy deformation had occurred within them.…”

“…In general, slipping is the predominant mode of deformation for materials those have medium to high stacking fault energy (SFE), while twinning is very popular in lower SFE materials, especially at high strain rates or very large strains [50][51][52]. It is known that the SFE of nickel-base alloy 718 is of an intermediate value, and it has been shown in some publications that twinning dominated the deformation process in alloy 718 under different mechanical treatments [51,53].…”