Exclusive: Corrosion and protection technology of aviation materials
FANG Bing, CHEN Haohui, WANG Shouze, TIAN Haoliang, ZHANG Shu'ai
The effect of alloying elements on the basic properties of associated metal coatings is investigated. A seamless steel pipe with diameter of Ф78 mm*8 mm*550 mm is selected, and a long groove of 150 mm*10 mm*4 mm is set in advance at 200~350 mm from the inner wall of the pipe to the end of the pipe, and the associated metal coatings with different contents of alloying elements are prepared by self propagating high temperature synthesis technology. The effects of different alloy elements on pores, cracks, hardness and corrosion resistance of associated metal coatings are then investigated by Vickers hardness measurement, electron microscopic scanning and acid immersion corrosion test. After adding Nb and Cr elements, the hardness of the associated metal layer increases, pores and cracks are obviously reduced, and microstructure tends to be homogenized. The corrosion resistance of the associated metal layer is directly proportional to the amounts of Cr and Nb, but the amount of ZrO2 has minor effect. The weight loss of associated metal coating with the best corrosion resistance is only 0.271 g, the weight loss rate is 2.71%, and the weight loss rate is only 21.22% of the pure iron layer. Addition of Nb and Cr can effectively improve the basic properties of the associated metal coating, while Zr has minor effect on the properties of the coating.