Failure Analysis Of Spray Coating In Coal Chemical Lock Valve

The coal chemical industry still occupies a very important position in the development of the national economy.The lock slag valve is a key component of coal chemical equipment.It works under the harsh conditions of high temperature,high pressure and flowing powder wear.Its service life directly affects the normal operation of the equipment and even leads to fatal accidents.In this paper,the failure causes of the failure parts of the lock slag valve under the friction and wear conditions are analyzed and summarized.It is proposed to prepare the wear-resistant protective coating of Ni60-WC by plasma spraying to improve the wear resistance and different at different temperatures.The tribological properties of WC coatings were investigated.The main results obtained are as follows:(1)Scanning electron microscopy and laser confocal focusing were used to characterize the micro-morphology of the coating on the slag lock valve.Through the analysis of the failure samples,it was found that there were cracks,wear and spalling phenomena in the failure coating.The failure of the coating was caused by excessive stress and wear.(2)The tribological properties of Ni60 and Ni60+WC coatings at different temperatures were compared and analyzed.The results show that the Ni60+WC alloy coating has high hardness and good wear resistance,and with the increase of WC,the coating can withstand and resist hard.The micro-cutting of the grinding head and the shaping deformation under repeated extrusion improve the wear resistance,and under the same load,the optimized coating wear amount is reduced.(3)Ni60+WC alloy coating was prepared on the preheated ball and seat by plasma spraying technology.The thickness of the hard coating is not less than 600?m,the hardness is 59 HRC,the hardness of the seat(forming the surface with the spherical surface)is 56 HRC,the coating has a low porosity(3%-5%),and its wear resistance is excellent.Wear resistance of thermal spray coatings.The improved technology is used on the valve surface.The valve has not been in operation for two years and the service life is significantly enhanced.