Surface roughening treatment of thermal spraying substrate and introduction of sandblasting

       Roughening treatment is to form a uniform uneven rough surface on the surface of the cleaned and pre-processed substrate to increase the contact area between the coating and the workpiece and to control the roughness of the coating. The roughened surface can produce a good mechanical bond with the coating. Correct roughening treatment can have the following effects.



    (1) The "anchor effect" is achieved, even if the deformed flat particles in the coating interlace with each other to form an interlocking stack.

    (2) Increase the area where the coating is combined with the substrate.

    (3) Improve the residual stress of the coating, make the coating produce compressive stress, and reduce the macroscopic residual stress of the coating. Creates a stronger bond between the coating and the substrate.

    (4) To further purify the surface, and play a role in activating the surface.

    The methods of roughening the surface of the substrate include sandblasting, machining (thread turning, slotting, plane cloth nails, etc.), electric brushing, etc.

     Sandblasting

     Sand blasting is a method of using compressed air flow or centrifugal force as power to spray hard abrasives onto the surface of the substrate at high speed, and roughening the surface by the abrasives scouring, chiseling and hammering the surface. Sandblasting and roughening also has the effect of surface purification, so as to remove rust, scale, burr, welding slag, old coating, etc. on the surface of the substrate, which has the effect of purification, roughening and activation. However, the surface of the workpiece substrate is directly sandblasted and roughened without thorough purification treatment, and the workpieces that only use surface purification treatment cannot be directly sprayed. Sandblasting can also generate a certain residual compressive stress on the surface, which is beneficial to improve the fatigue strength of the sprayed coating. In addition, sandblasting has high production efficiency and is especially suitable for surface pretreatment and on-site construction of large-area and mass production. It is the most commonly used surface pretreatment method in the industry.