Study On Technology And Properties Of High-silicon Aluminium Alloy Coating Prepared By Supersonic Plasma Spraying

High-silicon aluminium alloy is used in automobile engine,electronic packaging,aerospace and other fields because of its high strength,low thermal expansion coefficient,excellent wear resistance and thermal conductivity.At present,high-silicon aluminium alloy is mainly prepared by spray forming technology,but its process is very complex and the production efficiency is low,which makes the preparation cost of high-silicon aluminium alloy very high and restricts the application scope of the alloy.As high-silicon aluminium alloy mainly plays the role of wear resistance,and wear generally occurs on the surface of materials,therefore,a method of preparing a coating of high-silicon aluminium alloy by supersonic plasma spraying on the surface of ordinary materials was proposed in this paper.It can make the surface of materials have the same wear resistance as that of high-silicon aluminium alloy,and make the parts do not need to adopt high-silicon aluminium alloy as a whole,thus saving materials.It reduces the cost and improves the production efficiency.In this paper,Al-Si binary high-silicon aluminium alloy coating and multi-element high-silicon aluminium alloy coating were prepared by supersonic plasma spraying.By comparing their properties,it was determined that the multi-element high-silicon aluminium alloy coating had better properties.Then the spraying parameters were optimized.The morphology,microstructure,phase,microhardness,modulus of elasticity and bonding strength of the coating were analyzed and tested.Finally,the wear resistance of the coating under dry friction and oil lubrication with different loads were tested,and the wear mechanism under the two conditions were analyzed.The final conclusions are as follows:(1)It is feasible to prepare high-silicon aluminium alloy coatings by supersonic plasma spraying,and the coating have finer and denser microstructure,higher hardness than that of alloy prepared by spray forming,and coating have excellent wear resistance.(2)For Al-20 Si,Al-25 Si and Al-30 Si coatings,the higher the content of Si,the higher the hardness.But,the wear resistance of coating increased first and then decreased with the increase of Si content.Experiments showed that Al-25 Si coating have the best wear resistance,followed by Al-20 Si coating,and Al-30 Si coating have the worst wear resistance.However,the microhardness and wear resistance of Al-25Si-4Cu-1Mg coating were higher than that of three Al-Si binary high-silicon aluminium coating.(3)The structure of Al-25Si-4Cu-1Mg alloy coating was mainly composed of soft?-Al matrix and some hard particles of ?-Si,Al-Cu and Al-Si strengthening phases distributed on the matrix.The strengthening mechanism of high-silicon aluminium alloy coating was that the ?-Si,Al-Cu and Al-Si strengthening phases play the role of dispersion strengthening,and in the cooling process,the Si in ?-Al could hardly separate out,therefore,the Si play a role of solid solution strengthening.(4)The wear mechanism of Al-25Si-4Cu-1Mg coating under dry friction is abrasive wear and adhesive wear,accompanied by severe oxidation wear.With the increased of load,the tendency of adhesion wear and oxidation wear increased.The wear mechanism of coating under oil lubrication is abrasive wear and fatigue wear,accompanied by slight oxidation wear.With the increased of load,abrasive wear and fatigue wear increased.The wear resistance of the coating under oil lubrication is better than that of coating under dry friction.