High Temperature Resistant Wear Resistant Ceramic Coating On Metal Substrates

In the thermal engineering field,it is often faced problem that the inner wall of boiler needs periodic shutdown maintenance due to long-term flushing of the coal ash particles and high-temperature corrosion,which brings huge economic losses to enterprises and users.Many studies have shown that high temperature-resistant,wear-resistant,corrosion-resistant ceramic coatings on metal substrates can protect furnace walls and pipes to extend the service life of boilers.The ceramic coating has excellent properties such as high temperature resistance,high hardness,and corrosion resistance.If it is combined with toughness processability,electrical conductivity and thermal conductivity of metal materials,it will be widely used in industrial,aerospace,shipbuilding,energy materials and many other high technologies.This article focuses on the high temperature wear resistant ceramic coatings on metal substrates.The ceramic coating is mainly composed of three parts:ceramic aggregate?Al₂O₃,SiO₂ and SiC?,auxiliary materials?Cr₂O₃,MgO,kaolin,Al powder?,and inorganic binder?sodium silicate?.This article first studied the optimum addition amount of each powder of ceramic coating.The addition amount of aggregates and auxiliary materials are studied by changing feed ratio and orthogonal experiment method,and the results of thermal shock resistance and wear resistance are combined to determine the optimum amount of powder added.When the amount of Al₂O₃,SiO₂ and SiC added to aggregate is 1:3:1,the addition of auxiliary materials Cr₂O₃ and MgO is about 20%of aggregate,and the addition of kaolin is about 10%of aggregate,the addition of Al powder is about 2%to 10%of aggregate,and the coating performance is the best.Secondly,the effect of amount of binder added on wear resistance of the coating is explored.The results show that the best ratio of binder to powder is 2:1.The effect of addition amount of coarse SiC on wear resistance of the coating is also studied,and it is found that the optimal addition amount of coarse SiC is 30%.Finally,the best proportion coating is tested and characterized.The coating bears the thermal shock at900?and the phase analysis of coatings at different temperatures is carried out by XRD,and the higher temperature,the more complex coating phase.With the analyzing from SEM,there are no apparent cracks and obvious holes,indicating that the coating is compact.Considering the erosion resistance is one of most important points for coating,the acid-resistance is researched to demonstrate that the boiler with coating lose less mass than does boiler without coating.In order to improve wear resistance of the coating,gradient brush coating is used to improve the performance of coating on basis of the optimal coating.The results of wear resistance and hardness test show that the performance of the gradient brush coating is better than single coating.