Surface integrity-oriented grinding strategies for K444 superalloy: A comparative evaluation of conventional and superabrasive wheels

This study compares the surface grinding performance of four types of wheels (white fused alumina, microcrystalline alumina, vitrified CBN, and electroplated CBN) to meet the strict corrosion resistance and surface integrity requirements for K444 superalloy marine turbine blades. By analyzing grinding forces, temperatures, surface topography, and wheel wear, we aim to optimize wheel selection and parameters to suppress thermal damage and micro-defects. Results show K444 has poorer grindability than Inconel 718. Severe material adhesion and wheel wear are the primary machining challenges, frequently causing burns and surface defects. Grinding performance varies significantly with wheel type: alumina wheels achieve a maximum stable material removal rate (MRR) of only 0.33 mm³/(mm·s), though microcrystalline alumina offers better mechanical stability. Electroplated CBN provides the highest efficiency (MRR up to 5 mm³/(mm·s)) with low forces and temperatures, but leaves deep grooves susceptible to pitting corrosion. Vitrified CBN machines stably up to 2.5 mm³/(mm·s), yielding a uniform surface beneficial for anti-corrosion fatigue, but causes higher forces, temperatures, and severe abrasive wear flattening. Consequently, we propose a combined process strategy for highly corrosion-resistant blades: electroplated CBN for rough grinding, followed by vitrified CBN or microcrystalline alumina for finish grinding. This provides a proven basis for the high-efficiency, low-damage manufacturing of this alloy.