Study On Incident Dose Uniformity Of Ball Bearing Components Treated By PⅢ Batch Treating Process

Plasma immersion ion implantation (PIII) is an efficient treatment for ball bearing components because it overcomes the limits of conventional beam line ion implantation and can be used to modify surface with complex shape. However, only obtaining good uniformity on single component surface is not enough to apply the technique in bearing industry. How to get a good dose uniformity in batch treating process has been a key problem for the industry application. Since the dose distribution is affected by the sheath around the sample to be treated, controlling the sheath expanding process to avoid the sheaths overlap is very important for obtaining a good dose uniformity in PIII batch treating process.In this dissertation, a three-dimentional, rectangular-coordinated particle-in-cell (PIC) model was established to study the sheath expanding process around balls of the bearing in a PIII batch treating process. The influences of the bias voltage, plasma density and pulse duration on sheath expansion and incident dose distribution were studied. The theoretical simulation exhibits several results as follows. First, when the plasma density is identical, the sheath thickness and incident dose increases with the applied voltage increasing. However, the uniformity of the incident dose decreases because the sheath conformability is worse when the higher bias voltage was applied. Secondly, when the applied voltage is identical, with the plasma density increasing, the sheath thickness decreasing consequently, then higher incident dose and good dose uniformity are achieved. Lastly, sheath thickness increases with the pulse duration increasing from 5.0μs to 10.0μs when the bias voltage and plasma density are -10kV and 1.0×10⁹cm^-3 respectively, and the incident dose uniformity decreases from 80.67% to 78.20%.Pulsed high-voltage glow discharge was introduced into PIII batch treating process of ball bearing outer rings for the first time, and the plasma were generated successfully in the interior space of batch outer rings by glow discharge. A two-dimensional, cylindrical-coordinated PIC model for PIII batch treating process of ball bearing outer rings was set up for the first time, and the influences of with and without high density plasma supplementary on the sheath expansion and incident dose distribution were calculated. The simulation results suggest that we can obtain the high incident dose and good uniformity along the groove surfaces of ball bearing outer rings with high density plasma supplementary by pulsed high-voltage glow discharge. Secondly, the incident dose on the groove surfaces of outer rings locating at the end position is higher than the intermediate rings and the uniformity of all the outer rings is 86.87%. The intermediate position outer ring has the highest dose uniformity of 82.13% along the groove surfaces. In order to verify the reliability of the simulation, the implantation and deposition experiment were performed on batch treating outer rings and the implantation results have shown the same tendency as the simulation results. The deposition results show that the film thickness uniformity is better than implantation when a lower voltage was applied because the outer rings locating at end position do not have the advantages on ion quantities. It verifies the simulation results indirectly.A two-dimensional PIC model was set up to simulate the PIII batch treating process of ball bearing inner rings and the influence of laying styles of inner rings on the incident dose was investigated. The results show that the incident dose distribution on the groove surfaces is bad when there is a cavity structure in the interior space of inner rings because ions can be attracted into the cavity space by the electric field and consumed gradually in it. Consequently, the quantity of ions around the inner rings is reduced and the uniformity along the groove surfaces is bad also. Employing a cylinder to eliminate the influence of cavity structure, the incident dose has been improved and the dose uniformity can reach 98.88% except for the two locating at the end position. The simulation result was tested by the implantation experiment on the batch ball bearing inner rings with identical parameters. Based on the results of the simulation and experiment, two additional rings or others with the same dimension should be introduced into PIII batch treating process to guarantee the pretreated inner rings of ball bearing locate at the intermediate position and achieve a good uniformity of the incident dose.