C-N코팅 스퍼기어의 摩察·磨耗 特性에 關한 硏究
(A) Study on the friction and wear characteristics of C-N coated spur gear
C-N코팅스포기어 플라즈마이온주입 C-N coated spur gear 기계설계;
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Gear is the most important part in force transformation and the development of high strength, wear resistance, light weight, low noise gear has been an important subject until now. The main kind of failure generally occurred in gear is breakage and wear in the gear surface and many methods have been developed to improve the surface strength of the gear, including carburize, nitriding, carbonitriding, metallic cementation, laser surface hardening. However none of these methods is effective in improving all of the properties such as fatigue strength, high temperature hardness, wear resistance at one time. PVD(physical vapor decomposition) and CVD(chemical vapor de composition) can be used to modifying surface properties of different materials by enhancing, for example, corrosion resistance, hardness, friction coefficient and wear behavior. However, technological applications of these methods are limited by high cost, a sophisticated system for target movement and relatively high coating temperature when implanting three dimensional workpiece. PSII(Plasma source ion implantation) is developed as an alternative technology to circumvent these restrictions. This process has several advantages over conventional ion implantation, such as low cost, large area multiple targets and none-line-of-sight process. Furthermore, the components to be treated are immersed in a plasma and biased to a PSII allows an efficient carbonitriding of targets at temperatures sufficiently below than that of PVD and CVD, leading to improved tribological properties and retained mechanical strength and corrosion resistance. In recent years, the number of reports regarding PSII has increased rapidly. However, there seems little reports that apply this method in coating gear surface. In this study, a PSII apparatus has been built and the spur gear with steel substrate was treated with carbon nitrogen by it. The composition and structure of the surface layer were analyzed and compared with that of PVD coated layers for the sake of comparison. The following conclusions were drawn from present study: 1. Both of friction coefficient of C-N coating and TiNi coating decreased with increasing load, however, C-N coating showed relatively lower friction coefficient than that of TiN coating. 2. The vickers hardness of C-N film is 3200Hv, which was 32∼43% higher than that of TiN film. The critical load of C-N film was 52N, which was 25% higher than that of TiN film. 3. The hardness of C-N film fabricated by Plasma ion implantation was 61∼70% higher than that of base material, and friction coefficient was 14∼50% lower than that of base material, and the friction was changed from adhesive wear mode to light oxidizing wear mode. 4. The TiN coated gear showed a more serious friction phenomena than that of C-N coated gear. It was considered that coating of TiN, which was conducted at a vacuum chamber at about 500℃, results in a tempering of base material that causes microstructural change, which in turn resulted in decreasing of hardness. 5. The C-N coated gear and pinion had higher wear resistance that of TiN coated gear and pinion. C-N coating significantly improved the friction and wear resistance of the gear.