A compressor blade of martensitic stainless steel with complex surface and structure is difficult to machine, due to its wear and corrosion resistance. Mechanical polishing is widely employed to polish the blade, causing the surface roughness Ra >0.3 μm and profile tolerance >0.04 mm. To solve this challenge, a novel approach of immersed ultrasonic-assisted green chemical mechanical polishing (CMP) was developed, which was performed by a new custom-made polisher, regardless of complex surfaces and structures. Novel CMP slurry is proposed, containing silicon carbide, malic acid, serine and hydrogen peroxide. After CMP, surface roughness Ra of a compressor blade reduced from 0.668 to 0.085 μm, decreasing 87.2 %, and material removal rate is 87.6 mm3/h. Prior to and after CMP, profile tolerance is 0.028 mm. Transmission electron microscopy demonstrates that the thickness of damaged layer decreased from 280.16 to 15.24 nm, lowering 94.5 %. A mechanical model of a compressor blade is suggested to investigate the stress exerted by slurry, according to the calculations of computational fluid dynamics. X-ray photoelectron spectroscopy and Fourier transform infrared confirm that hydrogen peroxide oxidized the surface of compressor blade, forming oxides. The oxides were dissolved by the ionized H+ ions from malic acid and serine. Dissolved Fe2+, Fe3+ and Cr3+ ions were chelated by -COOH, -OH and -NH2 affiliated from malic acid and serine. Subsequently, soft oxide layer was removed by slurry. Our proposed novel ultrasonic-assisted green CMP offers new findings to achieve smooth surface with high profile tolerance on the surface of compressor blade, despite of its complex surface and structure.
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