Wear mechanism in high-speed superabrasive grinding of titanium alloy and its effect on surface integrity

Abstract

Single-layer electroplated cBN wheels offer several advantages over conventional wheels when grinding difficult-to-cut materials, in terms of improved workpiece surface integrity issues, such as lower grinding burn, fewer surface defects, and generation of compressive residual stresses. However, grinding behaviour e.g., grinding forces, temperature, and surface integrity, changes with wheel use while employing single-layer wheels due to progressive wheel wear as dressing is not conducted for them. Therefore, wheel wear and associated grindability studies like grinding forces and surface integrity are essential for the implementation of these wheels in the industry. The present study evaluates the wear mechanism of the electroplated cBN wheel and its effect on the grindability of Ti–6Al–4V. High grinding speeds (40 & 60 m/s) were employed under different cutting fluids environments (water-based soluble oil emulsion in minimum quantity cooling lubrication (MQCL) as well as in flood cooling modes and neat oil in MQCL regime). A lower cutting speed of 20 m/s is also chosen for benchmarking purpose. Grit fracture is found to be the primary mode of wheel wear. An elaborate discussion on the mechanism of cBN grit fracture is presented. It is observed that thermal shock-induced fracture has a dominant effect on wheel wear, and consequently, water-based fluid provided 2–4 times higher radial wear than neat oil up to 40 m/s. Because of lower radial wear, neat oil provided only 0–10% increase in grinding forces, 0–10% decrease in compressive residual stress, and almost the same level of surface redeposition with the progression of cumulative material removal. On the other hand, water-based fluid yielded 30–100% rise in grinding forces, 10–75% decrease in compressive residual stress, and a higher level of surface redeposition.