Microstructure And Properties Of Plasma Sprayed Al₂O₃ And Its Composite Coatings

Alumina ceramic coatings have been widely used in various fields of material protection due to their excellent properties such as high temperature resistance,wear resistance,and corrosion resistance,and have become one of the research hotspots.In this dissertation,?-Al₂O₃ and?-Al₂O₃ powders were used as coating powders respectively,and the alumina coating was prepared by plasma spraying.The morphology and properties of the coatings were analyzed by XRD,SEM and SRV,focusing on different processes of plasma spraying under the conditions,the phase transformation mechanism of?-Al₂O₃ as a powder preparation and its effect on the performance,and based on this,through the addition of aluminum powder in?-Al₂O₃plasma spray preparation of Al/Al₂O₃ composite coating of organization and performance.The specific research content and conclusions are as follows:Using?-Al₂O₃ as a spray powder,an alumina coating was prepared under different plasma spraying conditions.The roughness,hardness,porosity,and wear resistance were measured.The results show that the Al₂O₃ coating has excellent mechanical properties that the coating phase is?-Al₂O₃.The coating with?-Al₂O₃ phase as the main phase has a smooth surface with a roughness of about 4.46?m and a hardness of602.4 HV.Under the 10 N and 20 N loads,friction tests were performed with GCr15steel balls.The average friction coefficient of the coatings was 0.547 and 0.443.By measuring the depth of the wear scar,the wear volume of the coating is the smallest,about 2.5?m and 3.5?m,very slight,lower than the surface roughness,and the raised area of the coating surface is not flattened,and he wear resistance of the coating is more excellent.Using plasma spraying technology,alumina coatings were prepared with?-Al₂O₃and?-Al₂O₃ as spray powders respectively.The basic properties and friction and wear of two different powders were investigated.The results show that:?-Al₂O₃ The?-Al₂O₃ phase was the main phase for the preparation of the original powder.The hardness,porosity and wear resistance of the coating were better than those of the coating prepared with?-Al₂O₃ powder.The hardness was 614.7 HV and the porosity was 7.26%.and under the friction conditions of 10 N,15 N,20 N and 25 N,the wear of the Al₂O₃ ceramic ball respectively was 10.5?m,11.6?m,13.1?m and 14.5?m.The microstructure and properties of plasma sprayed Al/Al₂O₃ composite coating under different preparation process parameters were studied by adding 15 wt%aluminum powder in?-Al₂O₃.The results show that the current is 410 A and the voltage is 165 V,Al/Al₂O₃ composite has high wear resistance.Through friction tests with GCr15 steel balls,it has been found that the wear loss of Al/Al₂O₃ composite coatings at different normal loads is 40-80%less than that of a single Al₂O₃ coating,and the paired parts are that the amount of wear has also been reduced by 20%.