Metal thermal spraying materials
Metal thermal spray materials are a core component of metal thermal spraying technology. Their performance directly determines the quality and effectiveness of the coating, making them irreplaceable in the field of industrial surface treatment. These materials typically exist in the form of powders, wires, and rods. Depending on their chemical composition and function, they can be classified into various types, including pure metals, alloys, and metal-ceramic composites. They can meet diverse performance requirements, such as wear resistance, corrosion resistance, high-temperature resistance, conductivity, and insulation. Selecting the appropriate thermal spray material requires comprehensive consideration of factors such as the substrate material, operating environment, coating performance requirements, and the spraying process to ensure a good bond between the coating and the substrate, achieving optimal performance.
Pure metal thermal spray materials primarily include aluminum, zinc, copper, nickel, and iron. These materials exhibit excellent electrical and thermal conductivity, as well as corrosion resistance, and are widely used in anti-corrosion and conductive coatings. For example, zinc, aluminum, and their alloys are commonly used in anti-corrosion spraying of steel structures, protecting them from corrosion by forming a sacrificial anodic protective layer. Zinc coatings offer excellent cathodic protection and are suitable for humid, salt-fog environments; aluminum coatings, on the other hand, offer improved weather and high-temperature resistance, making them suitable for corrosion protection in high-temperature environments. Copper and copper alloys exhibit excellent electrical and thermal conductivity and are commonly used in the preparation of conductive and heat-dissipating coatings, such as those used on motor commutators and heat-dissipating coatings for electronic components.
Alloy thermal spray materials are composed of two or more metal elements. By adjusting the alloy composition, better properties than pure metals can be obtained, such as higher wear resistance, corrosion resistance, and high-temperature strength. Common alloy thermal spray materials include nickel-based alloys, cobalt-based alloys, and iron-based alloys. Nickel-based alloys have good corrosion resistance and high-temperature oxidation resistance, and are suitable for surface protection of components such as chemical equipment and turbine blades; cobalt-based alloys have excellent wear resistance and high-temperature resistance, and are widely used in the coating preparation of high-speed wear parts such as aircraft engine valves and bearings; iron-based alloys are relatively low in cost, and through appropriate alloying treatment, they can obtain better wear resistance and toughness, and are suitable for the repair and strengthening of general mechanical parts.
Metal-ceramic composites, composed of metal or alloy and ceramic phases, combine the toughness of metals with the high hardness, high-temperature resistance, and corrosion resistance of ceramics, making them a high-performance thermal spray material. The ceramic phase primarily includes aluminum oxide, zirconium oxide, tungsten carbide, and chromium carbide, while the metal phase, typically nickel, cobalt, iron, and their alloys, acts as a bonding agent for the ceramic phase. For example, tungsten carbide-cobalt (WC-Co) composites, with their extremely high hardness and wear resistance, are a preferred material for the preparation of wear-resistant coatings and are widely used in components subject to severe wear, such as mining machinery and oil drilling equipment. Aluminum oxide-titanium alloy composites, with their excellent high-temperature resistance and electrical insulation properties, are suitable for the preparation of high-temperature insulating coatings.
The morphology and particle size of metal thermal spray materials have a significant impact on the spraying process and coating performance. The particle size distribution of powdered materials should be uniform, generally controlled between 10-150 microns. Too fine a particle size can easily be carried away by the airflow during spraying, while too coarse a particle size can be difficult to melt, affecting the density of the coating. The wire diameter should be selected based on the spraying equipment and process parameters, typically between 1-3 mm. The wire surface should be smooth, free of oil and scale, to ensure a stable spraying process. With the advancement of materials science, new metal thermal spray materials are constantly emerging, such as nanostructured thermal spray materials. Their coatings have a finer grain structure and superior performance, meeting the higher performance requirements of high-end equipment. At the same time, the research and development of environmentally friendly thermal spray materials is also receiving attention. Low-toxic and harmless materials will gradually replace traditional toxic and hazardous materials, driving the development of metal thermal spray technology towards green and environmentally friendly methods.
