When designing the coating, we should first understand the service situation of the workpiece and the performance of the workpiece surface, and accurately determine the reason for the failure of the workpiece, such as the medium, temperature, the nature and size of the force, the material, organization and size of the workpiece, so as to determine the requirements of the coating. Including bonding strength, hardness, thickness, quantity and size of pores, surface accuracy, wear, corrosion, heat or other properties.
Abrasive wear coating refers to the coating that can withstand the cutting and grooving action of foreign particles between sliding surfaces, and the hardness of the coating should be greater than the hardness of foreign abrasive particles. The coating used at high temperature, its working temperature is 540~845℃; For coatings used at low temperatures, the operating temperature is limited to 540℃. When the working temperature is limited to below 540℃, the coating materials can be selected as self-melting alloy plus Mo or Ni/Al mixed powder, Ni/Al wire and self-melting alloy plus Co-WC mixed powder; When the working temperature is 540~845℃, iron, nickel, cobalt based materials, Ni/Al wire and Cr3C2 cermet powder are sprayed; When subjected to shock or vibration load, if the temperature is lower than 760℃, self-melting alloy is good; When the erosion is serious, Cr3C2 is used; Mainly used for oxidation resistance can be used iron, nickel, cobalt based coating.
The coating should have a high hardness, especially the surface hardness should exceed the hardness of the existing abrasive particles; The coating must have good oxidation resistance at operating temperature. Commonly used in mud pump piston rod (petroleum industry); Bushings for polished rods (petroleum); Suction pipe connecting rod; Screw conveyors for concrete mixers; Crushing hammer (tobacco products); Mandrel, dry cell electrolyzer; Grinding and polishing fixtures, etc.
Hardsurface wear resistant coating refers to a coating that is resistant to sliding wear of hard surfaces or soft surfaces containing hard abrasives. The coating shall be smooth to reduce wear and shall have an appropriate coefficient of friction. The working temperature of 540~845℃ is considered to be used at high temperature coating; The working temperature below 540℃ is considered to be used in low temperature coating. Coatings resistant to wear on hard surfaces used at low temperatures also include coatings resistant to wear on fibres and textile threads. When the working temperature is below 540℃, the coating can be used iron, nickel, cobalt based materials, self-melting alloys, non-ferrous metals, oxide ceramics, tungsten carbide and some refractory metal materials. When the operating temperature is 540~845℃, cobalt-based self-melting alloy, Ni/Al and chromium carbide coating materials can be used. When the temperature is lower than 760℃ and there is an impact load, the self-melting alloy should be selected. High temperature should be used Cr3C2 coating; For anti-oxidation, Ni/Al and so on were selected.
This type of coating should be higher than the paired surface hardness; When the matching surface is smooth, the severity of wear is reduced, and sometimes the wear is proportional to the roughness of the matching surface. The two surfaces in contact will produce debris, which can act as an abrasive; The hard particle will correspond to the hard part of the surface. Often used for drawing winch; Fork; Insert plug gauge; Rolling pipe sizing perforator; Extrusion die; Guide rod, etc.
