Advantages and Disadvantages of the Explosive Spraying Process

       The biggest feature of explosive spraying is to heat and melt the sprayed material with a sudden burst of thermal energy, and use the high pressure generated by the explosive shock wave to spray the molten particles to the surface of the metal substrate at high speed to form a coating. Its main advantages are as follows:



     (1) The bonding strength of explosive spraying is high. Because the sprayed powder is heated at a high temperature, and the molten particles fly at supersonic speed, the energy of collision with the surface of the workpiece is large, so the formed coating has a high bonding strength. When spraying ceramic powder, the bonding strength of the coating can reach 70MPa, while the metal The bonding strength of the ceramic coating can reach 175 MPa. According to relevant data reports, the bonding strength of the coating and the workpiece was as high as 240MPa.

     (2) The coating is dense and the porosity is low, generally less than 1%.

     (3) The wear resistance of the coating is high. When spraying, the powder particles are quenched after hitting the surface of the workpiece, and an ultra-fine structure can be formed in the coating, so the wear resistance of the coating is high. For example, in the friction test of Co-WC (w(Co) = 13%, w(WC) = 87%) coating and 50Mn friction pair, the friction surface temperature increased from 198 °C to 610 °C within 3 minutes, the coating wear The amount is 1/4 of the dual material 50Mn.

     (4) The hardness of the coating is high. The hardness of cemented carbide coatings is greater than HV1100, while the hardness of general flame and arc sprayed coatings can only reach HV800.

     (5) The roughness of the explosive spray coating is low, which can be lower than Ra=1.60um, and the roughness after grinding can reach Ra=0.025um.

     (6) During the spraying process, carbon decomposition and decarburization of carbide and carbide-based powder materials will not occur, so as to ensure the consistency of the composition of the coating and the powder.

     (7) The thermal damage of the workpiece is small. Explosive spraying is a pulse type, the workpiece is impacted by hot air for a short time, and N2 or compressed air cools the workpiece. Therefore, during explosive spraying, the temperature rise of the workpiece can be controlled below 100 °C, so no tissue phase will occur. deformation and workpiece deformation.

     (8) The thickness of the coating is easy to control, the machining allowance is small, and the maintenance operation is convenient.

     Explosive spraying also has disadvantages, mainly as follows:

     Explosive spraying is less efficient. The explosion frequency does not exceed 10 times/s, and the thickness of each sprayed coating is only 4-6um; during the explosion spraying, not only a strong noise (over 150dB) is generated, but also very fine dust particles are scattered everywhere, so it is necessary to It is carried out in a special soundproof and dustproof room, and the operation is controlled by a computer located outside the soundproof and dustproof room, which limits the application of explosive spraying; It is difficult to handle workpieces with complex shapes and small inner walls.