Characteristics and application of thermal sprayed composite core wire

       The composite wire for thermal spraying is another major development in the field of thermal spraying materials after composite powder materials. According to different structures and manufacturing methods, composite spraying wires can be roughly divided into the following categories:



1) Coated composite wire. It is to use the wire/tube composite method to put one metal or alloy wire into another metal or alloy tube, and draw it into a spray composite wire with a certain diameter.



2) Stranded composite wire. It is to use the wire/wire composite method to twist two or more different metal or alloy wires together, and then draw them into a spray composite wire with a certain nominal diameter.



3) Filled composite wire. It is to bond different metal or alloy powders, cermet powders, and ceramic powders with adhesives and fill them into metal or alloy tubes, that is, powder/tube composite method. The sprayed composite wire is made by extrusion, drawing and curing.



4) Dispersion metallurgical composite wire. It is to add a certain amount of ceramic particles or refractory material particles in the molten pool of metal or alloy by means of dispersion metallurgy, then ingot, extrude, draw, anneal, and finally make a composite wire with a certain diameter.



5) Flexible composite wire. It is a composite wire made by uniformly mixing powders of different materials and adhesives, extruding and curing.



Flexible composite wires can only be used for wire flame spraying because they are non-conductive. Other types of composite wires are suitable for both wire flame spraying and arc spraying. Composite spraying wire combines the advantages of composite powder and metal wire spraying, showing many features:



①It can be combined with a wide variety of materials, and can spray composite material coatings containing high alloy components, ceramics, cermets, intermetallic compounds, etc., overcoming the limitation that only metal wires can be used in the original wire spraying, and greatly expanding the sprayability The range of materials, and therefore the functions that can be prepared for coatings, is also wide and has a wide range of uses.



②The uniformity of wire feeding speed is easier to control than powder conveying. And the end of the wire is melted by the arc and then atomized into droplets and sprayed to form a coating, so there is no problem of unmelted "green particles" that may occur in the coating during powder spraying.



③ Compared with powder materials, the specific surface area of wire is much smaller. Therefore, when spraying metals or alloys and easily oxidized non-metallic ceramic materials (such as carbides) in atmospheric or oxidizing environments, the degree of oxidation or oxide content of composite wire spray coatings is much lower than that of powder spray coatings.



④The spraying rate of the composite wire is high. Compared with the powder plasma spraying, the energy consumption per unit mass of the spraying material, that is, the energy consumption ratio is much lower. The running cost of composite wire spraying is only about 1/9 of that of plasma spraying.



⑤The equipment cost is low and the investment is low. The cost of arc spraying equipment is only 1/8~1/5 of that of plasma spraying equipment.



⑥ The operation is simple and convenient, especially suitable for large-area spraying and on-site spraying.



With the improvement of arc spraying equipment and the stabilization and improvement of the quality of composite wire, the quality of arc sprayed coating of some composite wire can be comparable to that of plasma sprayed coating. However, in the arc spraying of the composite wire, the particle size of the sprayed particles is not uniform due to the effect of anode melting, and the surface of the sprayed coating is rough. Air atomization leads to serious burnout and oxidation of coating materials.