Study on the Arc Spraying Process and Properties of Aluminum Coating on AZ91D Magnesium Alloy
Huang Xiaomei
Because of a number of desirable features,such as high ratio of strength toweight and hardness to weight,good damping characteristic,electromagnetism screen characteristic,Magnesium alloys have a great potential for use in automotive,electronic,traffic,aeronautical industries and national defense industries,etc.However,heir applications are limited severly for the reason of their low corrosion resistance.
For the purpose of improving the corrosion resistance of Magnesium alloys,the aluminum coating on magnesium alloy was obtained by arc spraying technology in this paper.The samples with aluminum coating were prepared Different arc spraying technology parameters,and micro-hardness tests,pore proportion tests as well as bonding stregth of the aluminum coating were tested respectively.The corrosion resistance test of the coating was carried out in 5%NaCl neutral salt sulution.The effects of variation in the spraying parameters on the properties such as bonding strength,pore proportion,micro-hardness and mivrostructure of the aluminum coating have been investigated.
In order to improve the bonding strength and corrosion resistance of the aluminum coating,diffusion treatment was carried out.for the magnesium alloys with aluminum coating.According to the results in spraying process,it is indicated that spraying parameters,e.g.spraying electric voltage,electric current,the air pressure,and the spraying distance have a great important effect on the quality of the aluminum coating on magvesium alloy.Based on this,the optinmum process parameters was:obtained.They are the electric arc voltage 32V,the electric current 100~110A,the aire pressure is 0.6~0.75MPa,the spraying distance is 150mm.The corrosion resistance experiment in 5%NaCl neutral salt solution indicated that the corrosion resistance of magnesium alloy can be improved significantly by the aluminum coating by arc spraying.
The diffusion treatment for the magnesium alloy was conducted at 300℃、350℃、400℃ and 420℃ respectively for 2h.The mivro-hardness,bonding strength,thermal shock resistance and corrosion resistance of the aluminum coating were tested after thermal diffusion treatment.The test results indicated that a metallurgical bonding between the aluminum coating and the magnesium is created,and high micro-hardness,bonding strength and thermal shock resistance can be obtained for the aluminum coating on magnesium.
Keywords:magnesium alloy,aluminum coating,electric arc spray,mivrostructure
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