Spray Welding Process

Spray Welding involves reheating preheated self-fluxing alloy powder coatings to 1000-1300°C to melt the particles. The slag floats to the surface of the coating, and the resulting borides and silicides are dispersed within the coating, allowing for good bonding between the particles and the substrate surface. The deposited material forms a dense metallic crystalline structure, with a metallurgical bonding layer of about 0.05-0.1mm that has a bonding strength of approximately 400MPa. The coating exhibits good impact resistance, wear resistance, corrosion resistance, and a mirror-like appearance.

Compared to sprayed coatings, spray welded coatings offer significant advantages. However, during the remelting process, the substrate is locally heated to temperatures up to 900°C, which can cause considerable thermal deformation. As a result, the use of spray welding has certain limitations.

Components and materials suitable for spray welding are generally:
1. Parts subject to impact loads, requiring high surface hardness and good wear resistance, such as sandblasting machine blades, crusher teeth plates, and excavator bucket teeth.
2. Large, simple-shaped, easily worn parts, such as shafts, plungers, sliders, hydraulic cylinders, and chute plates.
3. Materials like low-carbon steel, medium-carbon steel (with carbon content below 0.4%), structural steel containing less than 3% of manganese, molybdenum, vanadium, nickel-chromium stainless steel, cast iron, etc.
Self-fluxing alloy powders are made from base materials like nickel, cobalt, or iron, with an appropriate amount of boron and silicon added. These elements act as deoxidizing slag-forming welding flux, while also lowering the alloy’s melting point, making them suitable for acetylene-oxygen flame remelting of the coating.

Domestic self-fluxing alloy powders come in various types. Nickel-based alloy powders exhibit strong corrosion resistance, oxidation resistance up to 650°C, and excellent wear resistance. Cobalt-based alloy powders have good red hardness, maintaining excellent wear resistance and corrosion resistance at 700°C. Iron-based alloy powders have better abrasive wear resistance than the other two types.