Friction And Wear Properties Of Mo And Mo Based Composition Coating For Piston Rings

The piston ring and cylinder composed a pair of friction components, are important mechanisms in internal combustion engine.And faced the internal combustion engine operation condition of the most demanding parts. Thermal spraying Mo and Mo composite coatings because of its excellent mechanical properties and tribological properties are widely used in manufacturing application and a wide range of piston ring coatings.In this paper, Mo coating and30 Wt.%Al2O3-Mo coating were prepared on 45 steel by atmospheric plasma spraying.Take the GCr15 ball as the grinding part.The HRS-2M type high speed reciprocating friction and wear testing machine was used to measure the friction coefficient of Mo coating Al2O3-Mo coating at different temperatures, under the condition of dry friction.and the load is 10 N to 40 N.Using Nano Map-500 LS 3D contact surface profiler to measure the cross-sectional area of the coating and calculate the wear rate.The microstructure and morphology of the coating were analyzed by JSM-5610 L scanning electron microscope.The wear mechanism of Mo coating at different temperatures was discussed.The results show:1.The porosity of the pure Mo coating produced by APS was 8.13% lower than that of the Al2O3-Mo coating,The hardness of Al2O3-Mo coating was 406.5±8HV higher than that of pure Mo coating,This is because the dispersion of the Al2O3 particles played a role in enhancing the hardness of the coating.The binding strength of the pure Mo coating was 42.2±3.2 MPa higher than that of the Al2O3-Mo coating,The addition of Al2O3 particles reduces the bonding strength of the coating,The inner bonding strength of the two coatings is higher than that of the coating and the interface of the substrate.2.The friction coefficient and wear rate of Mo coating increased with the increase of temperature and load,while wear with the GCr15 ball.At room temperature,the friction coefficient of Mo coating under 10 N to 40 N loading is 0.43~0.7,the wear rate is 0.59×10-5mm3/N?m to 2.989×10-5mm3/N?m.At room temperature to 300 degrees,keep the 30 N load unchanged,the friction coefficient and wear rate increase with the increase of temperature.When temperature rise to 300 degrees, the frictioncoefficient and wear rate increased to 1.14 and 11.2×10-5mm3/N?m.Compared with that of room temperature, it increased by 120% and 418% respectively.Under room temperature, the wear mechanism of Mo coating is plastic deformation and abrasive wear, the wear type might be single mechanical. When the temperature rise to 100 degrees to 300 degrees, the wear mechanism of Mo coating in friction and wear test is gradually changed into adhesive wear and more severe with increasing temperature.3.The wear properties of Al2O3-Mo coating are quite different from that of pure Mo coating while wear with the GCr15 ball,the coefficient of friction and wear rate change with the increase of the load, and the change of the temperature showed a trend of first increasing and then decreasing. The maximum wear rate is 8.01×10-5mm3/N?m under 300 degrees and the load of 30 N. Under room temperature, the wear properties of the pure Mo coating is better than that of the Al2O3-Mo coating. The high temperature tribological performance of Al2O3-Mo coating is better than that of pure Mo coating.The addition of Al2O3 increase the hardness of the coating and effectively inhibit the adhesion of the coating to the grinding material, especially in the temperature range of 100 degrees to 300 degrees. Which means the Al2O3-Mo coating has better friction properties than pure Mo coating under high temperature.