Research On Multiphase Composite Anodic Oxidation Film Of Aluminum Alloys Preparation And Mechanism

China is a high-speed sewing machinery manufacturing power. Friction parts is one of the core parts of equipment and it is a large proportion of the industry. In recent years, speed sewing machinery equipment is developing towards to no-oil operation. With high wear-resistant and self-lubricating properties of the friction parts material preparation technology research and development, is an important way to deal with the industry equipment lubrication without oil demand.7A04 aluminum alloy is commonly used in the preparation of friction parts of sewing machine. The traditional technique of improving the properties of aluminum alloy is preparation anodic oxide film. But the hardness is low, self-lubricating performance is poor, and it is difficult to meet the needs of high speed friction parts under the condition of lubrication without oil. Though the study of nanoparticles and polymer solid lubricant particles in multiphase composite anodizing technology, the preparation of high wear resistance and self-lubricating properties of composite oxide film has become one of the key research direction.In this paper, using sulfuric acid as the electrolyte and oxalic acid as additive. Multiphase compound hard anodic oxide film was prepared on the surface of 7A04 aluminum alloy. C-BN? ?-Al2O3?PTFE and Ce(SO4)2·4H2O) are composited in the wear-resisting coating. Using OM, SEM, EDS,micro-hardness tester and the wear test machine and other equipment to observe the structure, morphology and properties of the film. The results show that:1) Hard anodic oxidation with hardness of 389HV0.025 and thickness of 24?m is prepared. The best processes of oxidation are:150g/L sulfate, anodizing time is 30 min, pulse current density is 3A/dm2, wave type is DC overlapped pulse.2) The composite hard anodic oxidation film with hardness of 431HV0.025 and thickness of 28?m was prepared when the second phase content is 5g/L C-BN+3g/L ?-Al2O3+20ml/L PTFE+0.4g/L Ce(SO4)2·4H2O in the electrolyte. The four phase composite oxide film is more compact, inner diameter of nanotube is about 23nm. The friction coefficient is 0.097 and wear volume is 0.4mg. The multiphase composite coating has good wear resistance and self-lubricating properties.3) The composite hard anodic oxidation film which composited with 5g/L BN+3g/L Al2O3+20ml/L PTFE+0.4g/L Ce(SO4)2·4H2O were heat treated between 100? to 300?. The hardness of the film is 521HV0.025, the friction coefficient is 0.079, the wear value is 0.1mg. The composite film has excellent friction properties.4) Multiple phase particles were wrapped in film porosity, crack and shrinkage. The structure of multiphase composite anodic film is formed. it possesses hard particles reinforcing and soft particles anti-attrition properties. The hardness of the film is increased by adding hard particles, while PTFE mainly plays the self-lubricating function. Ce(SO4)2·4H2O promoted the growth of oxidation film.