The Study of the Friction Properties of AA6082 and AA7075 Material Journal Bearings Coated with Micro Arc Oxidation

In this study, AA7075 and AA6082 alloy bearing materials were coated with Micro Arc Oxidation (MAO) method by keeping the electrolyte composition, electric current, coating period, and coating thickness fixed. Tests were conducted on AA7075 and AA6082 material bearings coated and non-coated with Statically Loaded Journal Bearing Test Apparatus (SLJBTA) with 5, 10, 50, 100, 250, 500, 750, and 1000 rpm shaft speeds and under the static bearing loads of 150, 250 and 500 N with the lubricant temperature of 40 degrees C. Mineral-based oil was used in the lubrication of the test bearings. The friction coefficients (mu) occurring in the bearing were measured. Scanning Electron Microscopy (SEM) was used in the surface analyses of the bearing samples, and the material analyses were conducted with x-ray diffraction (XRD). It was determined from the experiments that while mu values were higher in both MAO-coated samples than the non-coated samples under the boundary lubrication conditions in low revolutions, the mu values of the coated samples decreased in high revolutions. Also, mu values increased in non-coated samples. In the aluminum alloys (AA6082 and AA7075), while MAO coating caused the mu values to increase under boundary lubrication conditions, it caused the mu values to decrease under liquid film lubrication conditions