Abstract:The spalling reason of the sprayed WC coating on the roller in the continuous hot-dip galvanizing line (CGL) was studied. The base material of the process roller is 45 steel, and the surface is sprayed with tungsten carbide coatings by High Velocity Oxy-Fuel (HVOF) spraying. After less than one year service, it is found that the spraying layer in the middle of the roller surface peels off. Aiming at the spalling of spray coating on roller surface layer on the roller surface, the composition analysis of the spraying material and the micro analysis of the coating are carried out. The analysis shows that the sandblasting process before spraying is very important. The residual sand particles can be found at the spalling places of the spraying layer. Through the analysis of coating cross section, it is further proved that in the process of sand blasting before spraying, the residual sand particles are not completely removed, which will lead to the peeling off of the spraying layer during the service.