Pretreatment Precautions Before Thermal Spraying

       Since the combination of the thermal spray coating and the substrate is mainly physical and mechanical mosaic, the bonding quality of the coating and the substrate is directly related to the cleanliness and roughness of the substrate surface. Therefore, the surface pretreatment becomes the entire thermal spraying operation. a very important part of it. Strict adherence to the procedures used in surface preparation is a prerequisite for the successful application of thermal spray coatings. In order to obtain good coating quality, the correct surface preparation method must be used. There are two important factors to consider when performing surface preparation: the first factor is the substrate material; the second factor is the spray material.



Machine parts subject to high stress must be carefully inspected using non-destructive testing methods before spraying to ensure that no defects exist in the base metal. If there are structural defects in the part, similar defects can also be produced in the prepared coating, which can seriously affect the coating quality. Especially when the gas, liquid, etc. in the working medium penetrate into the defect, if the defect is not eliminated before spraying, during the spraying process, due to the heating effect of the fuel flow and the sprayed particles on the substrate, the infiltrated liquid will cause the coating to spread to the coating. Surface diffusion, thereby contaminating the coating surface, affecting the bonding between the coating and the substrate and the deformed particles inside the coating, resulting in a decrease in the quality of the coating and even failure to form a coating. That is to say, it is not possible to use thermal spraying to repair the cracks in the substrate, and it is impossible to increase the strength of the substrate by thermal spraying.



In actual production, an appropriate surface pretreatment process should be selected according to the surface state of the actual parts. On the premise of ensuring the quality of the coating, a simplified surface pretreatment process should be adopted as much as possible to reduce the coating cost.