Fine Surface Finish of a Hardened Stainless Steel Using a New Burnishing Tool

The objective of this research is to develop a new ball-burnishing tool embedded with a load cell integrated with a CNC lathe, to improve the surface roughness and hardness of the fine turned SUS420J2 (equivalent to AISI420) stainless steel. The adequate ball burnish process parameters of the cylindrical part have been determined by conducting the Taguchi's L18 matrix experiments, the ANOVA analysis, and the verification tests. Based on the experimental results, the adequate combination of the process parameters is as follows: the ball material of WC, the burnishing force of 650 N, the feed rate of 0.05 mm/rev, the velocity of 25 m/min, the lubricant of the cutting fluid (oil/water concentration of 1/20) and the number of pass of 3. The fine turned surface roughness of the test specimen could be improved from Ra 1.1 μm to Ra 0.025 μm (Rmax0.202 μm) and the surface hardness could be increased from HRc 51 to HRc 52.5 on average using the adequate process parameters. Applying the adequate process parameters to a workpiece with different tapers, then the surface roughness could be improved from Ra 1.0 μm to Ra 0.04-0.06 μm on average.