Experimental analysis and performance evaluation of ball rolling process with developed new type rolling apparatus

The ball burnishing process is one of the most preferred surface methods. With the ball rolling method, improvements occur in the mechanical properties, surface roughness and surface hardness of the materials. The aim of this study is to experimentally analyze the ball burnishing process with a newly designed burnishing tool and evaluate its efficiency and to obtain improvements in the mechanical properties (such as wear resistance, fatigue and hardening) on the material surface. In this experimental study, the surface improvement process was applied by rolling AISI1050 steel material with a specially manufactured ball burnishing tool. The workpiece was first turned on a CNC lathe using a WNMG cutting insert for rough machining and then finished with a WNMG cutting insert to make it ready for rolling. Finally, the finishing operation was applied to the test samples and the ball rolling process was applied with the newly designed rolling apparatus. The experimental setup was determined according to the Taguchi L9 orthogonal experimental design and the experiments were carried out in this order. The rolling process was carried out with a constant rolling force, 3 different feeds and 3 different passes at a constant speed. These parameters were determined as 143N rolling force, 0.04-0.08-0.12 mm/rev feed rate and 3 passes at a constant speed of 600 (rev/min). With the determined parameters, the surface roughness and surface hardness values on the rolled AISI 1050 steel material were examined. Surface roughness values were taken from three different points of the burnished workpiece surface according to different pass numbers and feed rates, and the surface roughness value of that surface was determined by taking the arithmetic average of the values taken. The surface hardness values of the burnished workpieces were calculated by taking measurements at three different points on the microhardness device and the hardness values were found by taking the arithmetic average of these. The obtained surface roughness and hardness values were analyzed with Taguchi design. The effects of feed rate and number of pass on the surface roughness and hardness values were analyzed according to the Taguchi signal/noise (S/N) ratios. It was seen that the most effective parameter on surface roughness and hardness was feed rate. While the best surface roughness conditions were obtained at low feed rate and low number of passes, the best hardness values were obtained at low feed rate and increasing number of passes. As a result of the experiments and analyzes, it was proven that the ball burnishing tool specially designed according to the current standard turning criteria can be used in surface rolling processes.