Effect of process parameters on surface roughness of NiCu alloy in fluid jet polishing

Fluid jet polishing is a non-contact and flexible type of polishing process for generating high-quality surface finish in optical dies manufactured from ductile materials like Monel-400 (NiCu alloy). This article presents an investigation of fluid jet polishing of Monel-400 die material with a 3D printed Ti64 tool and silicon carbide abrasive slurry with an effect of pressure, stand-off distance and polishing time on the surface finish. The response surface methodology method was used to develop the experimental plan and Analysis of Variance analysis was carried out to identify the optimized values of the control parameters to maximize the percentage change in surface roughness. The validation of the developed regression model was done by polishing the plate of Monel-400 using the optimized parameters: the pressure of 9.6 bar, stand-off distance of 32.2 mm and polishing time of 170 s. The optimized fluid jet polishing parameters successfully generated a surface roughness of 90 nm in one of the experimental tests. The predicted results were in close agreement with the experimental results. Further improving the polishing efficiency, the optimal feed rate of 20 mm/min was used to polish the 40 mm × 50 mm Monel-400 plate, the surface roughness was reduced from 300 to 80 nm in 10 multiple passes showing the reduction in peaks and valleys with the surface improvement of 73.33%. The result shows that the fluid jet polishing process tends to improve the life span of Monel-400 die steel workpieces which is beneficial for the application of various industrial components such as optical lenses, marine applications, automotive components and defence applications.