Investigation into Grindability of Gh4169 Superalloy and Effects of Grinding Parameters on the Surface Integrity

GH4169, a nickel-base heat-resistant alloy, usually has outstanding high-temperature strength, excellent thermal stability and good wear resistance. However, it is hard to cut and its machined surface quality and integrity are particularly sensitive to a manufacturing process employed. The study reported in this paper was conducted to initially, review existing research on machining-induced surface integrity characteristics and machinability of some hard-to-cut materials, which was followed by a series of experiments focused on the effects of processing parameters on surface integrity of the GH4169 workpiece. Plain and external grinding tests were performed with various cutting parameters by using an Al2O3 wheel. For external grinding, an orthogonal test was designed to study the effect of the main grinding parameters on the surface integrity characteristics, which directly reflect the machinability of the material and its sensitivity to the specific grinding parameters. Machined surfaces were observed, and surface residual stress and microhardness were attained. Within a specified plain-grinding parameters range, additional measurements and observations beneath the ground surface were performed. The residual stress profile, the microhardness profile and the microstructure alteration below the machined surface were analyzed. It was shown that plain grinding with a low depth of cut (that is to say, low material removal rate) leads to potentially more acceptable surface quality with a lesser variation of residual stresses and microhardness values in the machining-affected zone than those obtained with high depth of cut. In addition, no severe microstructural alteration or adverse surface cracking will be discerned when the grinding parameter, depth of cut ap, is reasonably set. Keyword: grindability; surface integrity; surface roughness; residual stress; microhardness; microstructure