The Study On Microstructure And Properties Of Thermal-sprayed Coatings On Magnesium Alloy

Magnesium is very rich in reserves on the earth, but it isn’t widely used. With thedepleting reserves of many metal elements on the earth today, the sufficient development andutilization of magnesium resources can ease the pressure on the metal element consumption.Magnesium alloy, aluminum alloy and steel are known as the three structural metal materials,and magnesium alloy is the lightest one. Magnesium and magnesium alloy have manyadvantages, such as high specific strength, high specific stiffness, good electricalconductivity, and good thermal conductivity and so on. What’ more, magnesium alloy isgood properties in cutting and they can be reused by some simple treatment, as a result, theycause the concern by the experts. Because of the advantages above all, magnesium alloy hasbeen partially used in automobile manufacturing, electrical and electronic industry and so on,and it possibly has wide application prospects in transportation, aviation, aerospace anddefense industry in the future. However, magnesium alloy has its own shortage in the usingprocess. The main problem is that the chemical property of magnesium is active and the badwear-resistant performance. The shortages mainly reflect in the following two aspects, it canbe oxidized in the moist air and be worn seriously when it isn’t loaded. The two shortages ofmagnesium alloy have severely restricted the application of magnesium alloy. To solve theproblems, many scholars have taken a lot of researches at home and abroad. There are twomain solutions, one is adding alloying elements, and the other is surface modification. Manydeveloped countries improve the overall performance using the surface protection method,such as a variety of surface coatings, micro-arc oxidation treatment and chemical conversionfilm. However, the methods above all have their own inherent limitation. For example, thechemical conversion film cost is high, electroplated coating has the problem ofenvironmental pollution.This study uses the method of thermal spray to prepare the coatings on the surface ofmagnesium alloy. The microstructure and properties of arc-sprayed Al coating and plasmaspraying Al/Al₂O₃composite power coating are investigated. At the same time, the propertyof plasma spraying Al/Al₂O₃composite power coating is compared with the arc-sprayed Alcoating.Plasma spraying uses the rigid non-transfer plasma arc as the heat source, and uses the inert gas （Ar） as the shielding gas. The mixed powder is accelerated and it impacts thesurface of the base metal in a high speed resulting that the coating is formed. Plasmaspraying has many advantages, such as high flame stream temperature, concentrated energy,high density and so on. The purpose of the study is to improve the performance ofmagnesium alloy using the plasma spaying technology. Coating on AZ31B magnesium alloysurface is obtained by electro-arc spraying in order to improve the bonding strength. Basedon the wear test, whether the wear volume or the weight, the base material of Magnesiumalloy has maximum value, Al coating has a lower value, and Al/Al₂O₃composite powercoating has the minimum value. It is found from the microstructures of the coating made ofspecific parameters that coating have metallurgical bond region.It can be found according to the analysis of the coating that the coating which the basematerial of Al and reinforced phase of Al₂O₃particles is the optimal choice for improving theperformance of magnesium alloy. The research can supply the theoretical basis forimproving the comprehensive properties of magnesium alloy in future.