1. Advantages of metal spraying process
(1) It is suitable for a wide range of materials, and is not limited by the weldability of materials. The surfaces of various metals and nonmetals can be sprayed to obtain a better coating.
(2) There are a wide range of spraying materials, including metals and their alloys, ceramics, organic resins, etc.
(3) The spraying operation time is short, the temperature is low, and the deformation of the matrix material is small.
(4) The coating is of porous structure, which can store oil, and has good lubrication and wear resistance.
(5) The spraying equipment is simple, small in weight and easy to move, which is suitable for on-site construction.
2. Disadvantages of metal spraying process
(1) The bonding between the spraying layer and the substrate is mainly mechanical, and its bonding strength is far lower than that of the welded structure. The tensile strength of the coating itself is low, and it can not bear high line and point pressure.
(2) The sprayed layer has porous structure, which is conducive to lubrication, but not conducive to the corrosion of harmful media.
(3) When spraying, the fog points are dispersed, the splash loss is serious, and the metal adhesion rate is also low.
(4) Explosion proof, fire prevention and ventilation must be considered at the spraying site to prevent the evaporation gas or powder of harmful metals from harming human body.
3. Application of metal spraying process
(1) Wear parts: large or complex machine parts, such as crankshaft, roll journal, main shaft, transmission shaft, etc
(2) Defects of castings: repair of sand holes, pores and other defects in large castings
(3) Bearing bush material: a layer of aluminum bronze or phosphor bronze is sprayed on the bearing bush to repair or replace the integrally manufactured bearing bush
(4) Prevention of thermal corrosion: aluminum spray is used to strengthen the high-temperature oxidation and corrosion resistance of metal components, such as furnace door, furnace plate and gas turbine parts
(5) Prevention and mitigation of chemical corrosion: steel parts in contact with moist air, water, acid solution or gas shall be sprayed with a layer of corrosion-resistant materials (such as pure zinc aluminum alloy, tin, lead, copper, aluminum, zinc, stainless steel or corrosion-resistant non-metallic materials, etc.).
(6) Others: preparation of metal powder; Make electrical and electronic components, such as selenium rectifiers, resistors, etc.
4. Characteristics of plasma spraying process
(1) Spraying layer: the spraying is carried out by non transfer arc plasma jet. After the alloy powder enters the high-temperature jet, it immediately melts and shoots out with the jet at a high speed, spraying it onto the surface of the workpiece. The hot molten beads immediately produce intense plastic deformation and quickly cool into a solid plasmonic layer. Plasma jet has the characteristics of high temperature, fast flow rate and concentrated energy, which is conducive to obtaining dense and high bonding strength coatings
(2) Application: due to the high temperature root of contour sub arc and jet, it can melt high melting point materials. During spraying, the heat is concentrated, the base metal is heated less, the coating dilution rate is low, and the deformation of the sprayed workpiece is very small, so it is often used to spray important parts. In practical application, wear-resistant, heat-resistant, heat-insulating, corrosion-resistant, sealing and other coatings can be selected according to needs.