The Research On The Cold Spray Technique For Rapid Solidified Zn-Al Alloy Powder On The Magnesium Alloy And The Property Of The Coat

In this paper, a new method to protect the magnesium alloy from being corroded has been brought forth, i.e. coating the rapid solidified Zn-Al alloy powers on the surface of the magnesium with cold spray technique. The experiments have been carried on to study the producing of the Zn-Al alloy powers by using supersonic gas atomization equipments and optimizing the process of cold spray technology. The influence of the shape and grain size of powder and process parameter on the spray quality has been studied; Observation to the morphology of coat, analyze the bonding between the coat and the matrix and measure the hardness of the coat, bonding strength between coat and matrix, the hard wearing and corrosion resistance have been tested.The results show that the grain size of produced ZA20, ZA27 alloy powder for cold spray is homogeneous, and the phase of the coat is equal axis crystal. The segregation of Al elements is depressed obviously.The parameters of cold spray Zn-Al alloy powder on magnesium alloy surface are that: The pressure of spray gas to ZA20 alloy powder is 2.15MPa. The temperature spray gas to ZA20 alloy powder is 300℃ and the spray distance is 40mm. The pressure of spray gas to ZA27 alloy powder is 2.1MPa. The temperature spray gas to ZA27 alloy powder is 330℃ and the spray distance is 20mm.The compactness of the coat by cold spray has relation with spray pressure. When the spray pressure is low, there are many cavities, which are not connected between. With the increasing of the spray pressure, the compactness of the coat will increase as well. The temperature of cold spray can produce some effect on the quality of the coat. The spray temperature much lower than the melting point, the matrix and the powder have no melting phenomenon and there is no sintering or melting defects.The hardness of the coat is apparently higher than the matrix and the casting Zn-Al alloy. The coat has perfect bonding strength, and the wearing and corrosion resistance are both better than the matrix, which can protect the matrix from being corroded.