The Research On The Fatigue Wear Of DLC PCVD Coating

DLC film is a new coating with properties similar to the diamond thin film; it has high hardness, good thermal conductivity, low coefficient of friction, excellent electrical insulation properties, high chemical stability and IR transparency optical performance. DLC coating as a representative of high-quality hard coatings shows a wide range of applications in different areas, the research about it has been a hot issue. But there are many factors affect the processes of coating and friction and wear, the research on coating fatigue wear mechanism and failure mechanism are not enough at present. In this paper, used Plasma Chemical Vapor Deposition method spray DLC films on the surface of 45 steel, with 45 hardened steel composed the roll-slip friction pair. We made the fatigue wear test in different conditions including full contact, horizontal reciprocating motion and vertical motion on M-2000 wear tester. With test data and phenomena, the investigation is on friction and wear properties and fatigue wear mechanisms under different conditions of DLC coating.The results of the experiments show that:(1) At full contact conditions: the increase in the load leads to the initial decrease in the frictional coefficient and then increase, and a lowest frictional coefficient of 0.205 appears at 250N; at horizontal reciprocating conditions: the slow decrease in the frictional coefficient was caused by the increase in load, and frictional coefficients of 0.213 and 0.178 appears at 100N and 300N, respectively; at vertical reciprocating conditions: the frictional coefficient was initially enhanced and then followed by a decrease trend; the highest frictional coefficients of 0.640 appears at load of 200N. (2) The wear rate was slightly enhanced as the load is lower than 200N, and was sharply increased with the further increase in the load. The lowest wear rate was 1.55 mg/10000r, and the highest wear rate was 15.6mg/10000r. (3)Comparing the average friction coefficient and the wear rate with load curve under different conditions, it can be found DLC coating under reciprocating motion in the horizontal has a good anti-wear effect, vertical motion under the worst.Based on the experimental study of DLC coating in the fatigue wear mechanism under different conditions: (1) at full contact conditions with low loads, the wear mechanism is pit corrosion and peeling removal; at high load, the wear mechanism shows peeling removal. (2) At horizontal reciprocating movements, the wear process is complicated. The adhesive wear and fatigue wear dominates the wear process. The formation of the transition chemical layer in the wear process reduces the frictional coefficient and wear rate. (3)at vertical reciprocating movements, the wear mechanism is shown impact removal. At low load, the adhesive wear dominates the wear process; On the contrary, the abrasive wear plays the essential role to remove the material. (4) According to coating damage cycling times of fatigue wear under different loads, drawing DLC coating in case of dry friction fatigue wear F-N curve, initially established the physical model of stripping film of the substrate under the impact.