Oxidation Mechanism And Deoxidation Technology Of Cu-Pb-Sn Bearing Alloys

Cu-Pb-Sn alloys have high strength,high plasticity and good anti-friction performance.Therefore,it is used as a bearing alloy layer for sliding bearings.However,with the development of military and industry,the engine rotating speed and bearing capacity of tanks,armored vehicles and automobiles are increasing.Bearing alloys need to withstand higher loads and have better antifriction properties.Therefore,Anti-friction coatings need to be applied to the steel back/bearing alloy double-layer alloy surface.However,due to the limitation of conditions,if the coating process cannot be fast,the copper-based bearing alloys are easily oxidized.And the oxidation products will hinder the combination between the coating and the bearing alloy,reducing the bonding force and affecting the quality of the coating and its application.First,the oxidation kinetics of Cu-Pb-Sn alloys at 25?,180?,300?,500?,and 700?were studied.After that,the surface of the oxidized Cu-Pb-Sn alloy was chemically cleaned and plasma cleaned,and the effects of different cleaning processes on the surface morphology and the degree of deoxidation were studied.Finally,AlSn20 coating was prepared on the surface of the material after cleaning by magnetron sputtering technology,and the influence of different cleaning processes on the structure and properties of AISn20 coating was investigated.Scanning electron microscope,transmission electron microscope,and white light interferometer were used to observe the surface morphology,cross-section morphology,and three-dimensional morphology of oxides and coatings.X-ray diffraction was used to analyze the phase of the oxidation products;The hardness tester was used to test the hardness of the anti-friction coating,and the scratch adhesion tester and pin-disk friction and abrasion tester were used to test the film-based bonding force and tribological properties of the coating.The width and depth of the friction trace were measured after the friction and abrasion test.Research shows:(1)During the oxidation of Cu-Pb-Sn bearing alloy,Cu and Sn are oxidized to CuO,CuO2 and SnO2.At 500?,Pb are oxidized to Pb3O4,and at other oxidation temperatures the oxidation products are PbO.During oxidation,Pb could easily form diffusion channels in the alloy and form PbO on the surface.While the oxidation temperatures are different,the surface morphology of PbO also could different.At 25?,there is no significant change;at 180? and 300?,the surface morphology of PbO is spherical;at 500?,in addition to the spherical shape,many fine whiskers of Pb are distributed on CuO;at 700?,the alloy surface is covered with small granular PbO and large spherical PbO.When the oxidation temperature is 25?,the oxidation weight increase curve of Cu-Pb-Sn alloy conforms to the linear equation;when the oxidation temperature is 180?-700?,the oxidation weight increase curve of Cu-Pb-Sn alloy conforms to the parabolic equation.(2)After the chemical cleaning,the oxide on the surface of the sample can be effectively removed,at the same time the surface morphology is improved,the bonding strength between the coating and the substrate is improved,and the performance of the coating is increased.As the reaction temperature rises,the surface oxygen content of the sample first increases and then decreases;as the H2SO4 concentration increases,the sample surface oxygen content gradually decreases.When the reaction temperature is 50? and the H2SO4 concentration is 15%,the surface oxygen content reaches to 2.3%as minimum value.After chemical cleaning,the surface was magnetron sputtered.The study found that after the chemical cleaning,when the surface roughness is 147.90 nm,that is the cleaning temperature is 50? and the H2SO4 concentration is 12%,the AlSn20 coating has the best density and integrity,and the surface roughness is the smallest,at 1.616 ?m.At this time,the hardness value reaches maximum value as 94.4 HV0.3,the film bonding force reaches a maximum value of 68 N,the minimum friction coefficient is 0.39,the depth of friction trace width is 562.48 ?m,and the wear scar depth is 28.4?m.The wear mechanism is mainly abrasive wear.(3)When vacuum plasma glow cleaning is used,the research found that:when the substrate is negatively biased at-600 V,the surface is the most flat and the surface roughness is the lowest at 89.52 nm;when the cleaning bias is-800 V,the surface oxygen content is the smallest.The average oxygen content is 0.7%.Therefore,with the increasing of the cleaning bias,the degree of deoxidation shows better.However,if the bias is too large,the surface atoms are sputtered to generate etching holes,and the surface performance are reduced.After plasma cleaning and coating by magnetron sputtering technology,it is found that as the cleaning bias increases,the surface roughness of the AlSn20 coating sample decreases first and then increases.When the bias is-600 V,the roughness of surface value of is the smallest,1.762 ?m;the surface hardness of AlSn20 coating and the bonding strength of the film base increase first and then decrease.When the cleaning bias is-650 V,the coating hardness reaches a maximum of 96.4 HV0.3,and the film base bonding force reaches the highest value,57 N;the surface friction coefficient of the AlSn20 coating decreases first and then increases.When the cleaning bias is-650 V,the average friction coefficient reaches a minimum value of 0.37,and the surface of the wear scar is the most flat,with a minimum wear scar width of 561.96 ?m and a wear scar depth of 28.5 ?m.The main wear mechanism is abrasive wear.