Preparation Of Gradient Al-Glass Coating On The Surface Of 6063 Al Alloy With Atmospheric Plasma Spray Process

There are great differences of physical properties between metal and glass so that there are great interface stress and poor cohesions between them. In this work, Al-Glass composite coating with gradient structure through atmospheric plasma spray was proposed to improve the cohesion between 6063 aluminium alloy and glass. On the basis of the research of deposition behavior of Al/SiO2 composite powders with different SiO2 volume through atmospheric plasma spray, the deposition layer turn was drawn out. The Al/SiO2 composite coating with gradient structure was prepared.Microstructure and properties of the composite coating with gradient structure were investigated.The deposition results of the Al/SiO2 composite through atmospheric plasma spray showed that the coatings with Al-to-SiO2 volume of 0:100,20:80,40:60,60:40,80:20 had the thickness of 100μm,50μm,40μm,50μm and 80μm, respectively. There were cracks between substrate and coating, which was especially obvious in the coatings with Al-to-SiO2 volume of 0:100, 20:80. During the deposition of Al/SiO2 composite, there were interface reactions between aluminium and silica powders. Two new phases of Si and Al2SiO5, which would enhanced the cohesions between aluminium and silica powders, were generated in the reactions. The interface reactions became more obvious with the decrease of the SiO2 volume. Therefore, Al/SiO2 powders with Al-to-SiO2 volume of 60:40,80:20 were more suitable to coating deposition through atmospheric plasma spray. With the increase of the SiO2 volume in AI/SiO2 composite, the composite coating hardness became greater and the adhesion between substrate and coating became poorer. Therefore, the coating deposition turn from substrate. NiCrAl bonding coat, Al/SiO2(80:20), Al/SiO2(60:40). Al/SiO2(40:80). Al/SiO2(20:80) to 100%SiO2 was drawn out for Al/SiO2 composite coating with good properties.The microstructure of the Al/SiO2 with gradient structure transit continuously. There were no obvious stratified interfaces between substrate and coating, each gradient layers. The change of the hardness of different layers in the gradient Al/SiO2 composite coatings were similar to the ones in the coatings with different SiO2 volume. The adhesion strength of the gradient Al/SiO2 composite coating was higher than the ones of the coatings with Al-to-SiO2 volume of 0:100, 20:80,40:60, while lower than the ones of the coatings with Al-to-SiO2 volume of 60:40,80:20.The Al/SiO2 composite coatings with gradient structure prepared through atmospheric plasma spray had good cohesions between Al and SiO2, excellent properties. The research realized good cohesion between metal and SiO2. The application of SiO2 was broadened.