Study On Tribological Performance Of Molding Machine Guide Rail Based On Surface Texture

During sand molding machine producing a sand core,the sand of casting material is inevitably embedded between the static and the moving guide rails of the molding machine.When the guide rails movement,the sand particles plow the rail surface and causing severe abrasive wear of the rail.The worn rail reduces the machining accuracy of the molding machine and shortens the service life of the machine tool.In order to improve the tribological performance of the guide rails of the molding machine,a textured surface and a composite surface with surface textured and surface-enchanced were performed on the specimen surface respectively.Analyze the effect of above measures on tribological performance of friction pair.The main conclusions obtained are as follows:Study the effect of groove texture parameters on bearing capacity by establishing a CFD model.The results show that the groove texture can improve the oil film bearing capacity,and is conducive to the formation of a lubricating film.Under oil lubrication conditions,the average friction coefficient of single-layer grooved texture of S2(h=0.05 mm,w=1.0 mm,Sp=34%)was 12.7%lower than that of the untextured sample of S1.When the volume of the single-layer groove texture is the same as that of the double-layer groove texture,the vortex area of the fluid in the texture can be reduced by changing the depth of the first layer groove of the double-layer groove texture,thereby significantly increasing the bearing capacity of oil film,which is beneficial to improve the lubrication performance.The tribological properties of grooved surface under sand-containing lubrication were studied.When the sand concentration is 5%,the volume wear rates of the textured samples of S4(h=0.40 mm,w=1.0 mm,Sp=34%),S5(h=0.50 mm,w=1.0 mm,Sp=34%),S7(h=0.40 mm,w=1.5 mm,Sp=34%)and S9(h=0.40 mm,w=1.0 mm,Sp=45%)are respectively 1/4.0,1/4.3,1/5.3 and 1/4.8 of the un-textured sample of S1.The surface texture significantly increases the wear resistance of the friction pair.When the sand concentration is 10%,the average friction coefficient and the wear rate of textured samples are higher than that of the untextured sample.When the sand concentration is high,an impact occurs between the sand particles and the edges of the grooves on the disk sample,which is detrimental to the improvement of tribological performance.The SEM shows that the wear mechanism of the textured samples and the un-textured sample are abrasive wear.The wear resistance can be significantly improved by laser cladding of the wear-resistant coating and surface nitriding to increase the hardness of the surface of the friction pair.The initial friction coefficient of the enchanced surface was significantly lower than that of the substrate surface under the condition of sand-containing lubrication.And the wear resistance of the laser cladding coating surface and nitriding surface is 2.6 times and 3.7 times higher than that of the substrate surface,respectively.Based on the tribological system theory,the influence of different friction pairs on the wear resistance was studied.The P1 friction pair(un-nitrided pin sample+un-nitrided and un-textured disk sample)was used as a reference in all friction pairs.Compared with P1,the P2 friction pair(nitrided pin sample+un-nitrided and un-textured disk sample)exacerbated the wear of disk sample,but other friction pairs are beneficial to improve the wear resistance of the disk sample.The P8 friction pair(nitrided pin sample+nitrided and textured disk sample)has the best improvement in wear resistance,and the wear resistance is 17.1 times higher than that of the P1 friction pair.In the P8 friction pair,the main wear mechanism of the disk sample was surface scratches,and the main wear mechanism of the pin sample was slight abrasive wear.