What Is Metal Spraying?

Metal spraying is a material protection technology that uses high-speed particle flow of molten metal to spray on the surface of the substrate to produce a coating.

Metal spraying is the spraying of high-speed particles of molten metal on the surface of a substrate to produce a coating.

The most widely used metal materials are zinc, aluminum and aluminum-zinc alloys, which are mainly used to protect large structural parts of steel. In 1952, China successfully sprayed zinc on the upper part of 264 35 kV transmission and transformation towers in Huainan Power Plant, saving a lot of maintenance costs. Spraying aluminum is more suitable for components working in harsh industrial atmospheres and marine atmospheres than spraying zinc. At the same time, it also has wear resistance, high temperature oxidation resistance and resistance to sulfur compound gas corrosion.

The characteristics of metal spraying are: there is no upper limit on the size of the workpiece, the heating of the substrate generally does not exceed 200 ° C, and the adhesion between the coating and the substrate can reach 7 MPa. After spraying

For mechanical repair. Carbon spray wire or spring wire can be used to repair worn crankshafts and drive shafts of machine tools. Spraying Cr13 steel can repair large extrusion hammer heads. After arc spraying, it is necessary to use phenolic resin to seal and hammer to close the pores, and then perform machining and polishing. The arc method is used to spray weld the heat-resistant and wear-resistant nickel-chromium alloy layer, which can repair large steam heating rollers.

For mechanical parts resistant to strong chemical media. For example, the plunger of the acidified fracturing truck used for oil production often works in 15-28% hydrochloric acid, and can be sprayed with nickel-chromium-boron-silicon self-fluxing alloy by plasma torch. Spraying titanium or titanium tantalum layer in a protective atmosphere by arc or plasma method can prevent the inner surface of the pump casing and the stirrer from being corroded by oxidizing acids containing chloride ions.

Used to improve the wear resistance of mechanical parts. Plasma spray welding of high-chromium cast iron on ordinary steel plates can extend the service life of the central slot plate of a coal conveyor. Thousands of parts in large aircraft engines are sprayed with metal, cermet and refractory materials, and the overhaul period can be extended from 4000 hours to 16,000 hours.

It is used to improve other friction properties of mechanical parts. in

The arc spray gun commonly used in the machinery industry is suitable for metal wire spraying. Flame spray guns are suitable for spraying metal wires as well as cermets and refractory oxides. Plasma arc spray gun and plasma spray welding are suitable for spraying various powders. Arc and flame spray guns are used for general anti-corrosion and repair. Among them, spraying zinc and aluminum can spray more than 200 kilograms per hour; for other functional, such as dense coatings, high adhesion requirements, etc. Adopt high-energy plasma spraying and vacuum high-energy plasma spraying. The spraying speed of explosive coating equipment can reach 2 to 3 times the speed of sound. It is suitable for spraying metals, especially cermets and refractory oxides.

In order to ensure the economical and high-quality metal spray coating, in addition to the proper choice of spray method and spray material, pre-spray and post-spray treatment are also necessary steps. In order to improve the adhesion, the functional metal often needs to be blasted before spraying, and then the bonding layer (nickel, molybdenum, etc.) is sprayed, or the surface to be sprayed is threaded or slotted. Cohesive coating. After spraying, the quality of the sprayed layer is inspected, and the necessary sealing treatment and corresponding finishing are performed ^[1] .