Effect of groove textures on tribological properties of 40CrNiMoA steel under starved grease lubrication

Abstract 40CrNiMoA steel is widely used in important mechanical parts under starved lubrication, such as shafts, gears and flexsplines for harmonic reducers. To improve the tribological properties of 40CrNiMoA steel and prolong the service life of the material in practical application, micro-grooves were fabricated on steel discs by laser texturing. The texture areal density is controlled by the number and width of the micro-grooves. The friction tests were carried on a ball-on-disk friction tester. The worn surfaces were observed by a scanning electron microscope and a three-dimensional microscope to discuss the friction and wear properties of textured discs under starved grease lubrication. The results show that the groove texture can effectively improve the tribological performance of the 40CrNiMoA steel. After optimizing, the tribological properties were greatly improved. The average friction coefficient reduced from 0.259 to 0.116 and wear rate was reduced by about 46 times. The contact stress of ball and textured discs was analyzed, the results shown that larger width of groove lead to higher contact stress, which may increase friction and wear. Therefore, storing lubricants and increasing contact stress should be balanced to obtain better tribological performances. In this study, the preferred range of texture areal density is 10% ∼ 22%.