Functions and applications of thermal spray coatings
One of the core functions of thermal spray coatings is to provide excellent wear resistance, significantly extending the service life of machinery under abrasive conditions. They are widely used on vulnerable parts in industries such as mining, metallurgy, and building materials. Wear is one of the main causes of component failure in industrial production, and can include various types of wear, including abrasive wear, adhesive wear, and fatigue wear. Thermal spray coatings can be specifically designed to combat different types of wear by selecting appropriate materials and processes. For example, on the surface of the crusher jaw plate of mining machinery, a tungsten carbide-cobalt coating with a hardness of up to HRC65 is applied using a high-velocity flame spray. This coating reduces the volume loss from abrasive wear by only one-tenth that of ordinary high-manganese steel, extending the jaw plate’s service life from one month to over six months. In the metallurgical industry, plasma-spraying a high-chromium cast iron coating on the surface of rolling mill rolls effectively resists adhesive wear and thermal fatigue wear, increasing rolling capacity by more than three times and reducing downtime for roll replacement. Furthermore, flame-spraying nickel-based alloy coatings on agricultural machinery components such as plowshares and harvester blades can significantly improve wear resistance and reduce maintenance costs.
Corrosion protection is another important application area for thermal spray coatings. By forming a dense barrier layer or sacrificial anodic coating on the metal surface, it protects the substrate from corrosive media. This coating plays a key role in fields such as petrochemicals, marine engineering, and municipal construction. Zinc, aluminum, and their alloys are the most commonly used anti-corrosion materials for ferrous metals such as steel structures. Zinc-aluminum coatings formed using arc spraying provide long-term corrosion protection for the substrate through both sacrificial anodic protection and physical isolation. On the steel legs of offshore platforms, arc spraying an 80μm-thick zinc-aluminum pseudo-alloy coating, combined with a sealer coating, offers salt spray resistance of over 5,000 hours, extending the corrosion life of the steel structure from five years to over 20 years. Plasma spraying a nickel-based alloy coating on the inner walls of oil pipelines protects against corrosive media such as hydrogen sulfide and carbon dioxide in crude oil, extending the pipeline’s service life by more than fivefold and reducing the risk of leaks. Flame-spraying aluminum wire coatings on steel structures such as bridges and sluice gates in municipal engineering projects also effectively resists atmospheric and rainwater corrosion, reducing maintenance frequency and costs.
Thermal spray coatings offer excellent high-temperature resistance and insulation, protecting the stability and safety of metal components in high-temperature environments. They are widely used in high-temperature applications such as aerospace, energy, and power generation. Plasma-sprayed zirconium oxide coatings on surfaces such as aircraft engine combustion chambers and turbine blades leverage their low thermal conductivity ( 0.1-0.3 W/(m · K) ) and high melting point ( 2700 °C) to form an effective thermal barrier, reducing substrate temperatures by 100-300 °C and ensuring proper engine operation at temperatures exceeding 1000 °C. Nickel-chromium-aluminum-yttrium alloy coatings applied to boiler superheater pipes in thermal power plants resist high-temperature oxidation and thermal corrosion, extending the pipe’s service life from 10,000 hours to over 20,000 hours. Furthermore, flame-sprayed alumina-zirconia composite coatings on the inner linings of industrial kilns improve thermal insulation efficiency, reduce energy consumption by 15%-20%, and extend maintenance intervals.
Thermal spray coatings also offer diverse functions, enabling specialized applications such as conductivity, insulation, sealing, and repair, meeting the personalized needs of diverse industries. In the electronics industry, arc-sprayed pure copper coatings are used on motor commutators. Their excellent conductivity, low contact resistance, and wear resistance ensure efficient and stable motor operation. In electrical equipment, plasma-sprayed alumina coatings serve as insulating layers for transformer cores and high-voltage switches, boasting breakdown voltages exceeding 10,000V and reliable insulation. In mechanical manufacturing, thermal spray coatings are often used to repair worn components, such as journals and bearing seats. Arc-spraying a nickel-based alloy coating restores the original dimensions and fit, costing only one-fifth to one-third of replacing a new part. An automotive engine manufacturer uses this technology to repair crankshafts, saving over 10 million yuan annually. In the sealing sector, flame-sprayed nickel-coated graphite coatings are used on valve sealing surfaces. Leveraging the self-lubricity of graphite and the wear resistance of nickel, they achieve leak-free sealing, with significant success in chemical pipeline valves.
The application of thermal spray coatings continues to expand in emerging sectors, providing innovative solutions for high-end manufacturing and green industries. In the new energy sector, wind turbine gearboxes are coated with tungsten carbide using supersonic flame spraying to improve fatigue and wear resistance, extending the gearbox service life from 20,000 hours to over 30,000 hours and reducing maintenance costs. Cold-spraying titanium alloy coatings on fuel cell bipolar plates ensures excellent conductivity and corrosion resistance while reducing material costs, promoting the commercialization of fuel cells. In the environmental protection sector, thermal spray coatings are used to protect waste gas treatment equipment from corrosion and wear. For example, nickel-based alloy coatings are sprayed on the heating surfaces of waste incinerators to resist corrosion and wear from high-temperature flue gases, extending equipment life. Ceramic coatings are sprayed on wastewater treatment equipment to prevent acid and alkali corrosion and improve operational stability. These emerging applications not only expand the functional capabilities of thermal spray coatings but also provide strong support for technological upgrades and sustainable development across various industries.
