VALVE MAGAZINE Winter 2025

PROTECTIVE COATINGS FOR VALVES

HVOF material options Several types of materials can be HVOF coated, and the specific material chosen depends on the desired properties for the application. Here are some of the materials commonly used with HVOF coating: Metallic Materials • Stainless steels: These offer excellent corrosion resistance, high strength and wear resistance. Examples: 316L, 904L, 410 • Nickel alloys: Often used for applications requiring high resistance to heat and oxidation. Examples: Inconel 625, Inconel 718, Monel • Cobalt alloys: Known for high wear resistance, good corrosion resistance and high-temperature stability. Examples: Stellite 6, Stellite 21 • Iron alloys: These can be used to improve wear resistance in some cases. Examples: Hardened steel, cast iron • Titanium alloys: Useful for applications needing a combination of strength, low weight and corrosion resistance. Examples: Ti-6Al-4V, pure titanium (Grade 2 & 5) Carbide Materials • Tungsten carbide (WC) coatings: These are widely used in applications where wear resistance is a priority, such as in mining, drilling and other harsh conditions. • Chromium Carbide (CrC): Provides excellent wear resistance and is used in various applications, including oil and gas, petrochemical, mining and cement industries. Composite Coatings • WC-Co (Tungsten Carbide-Cobalt): Composite coatings often combine hard ceramics like tungsten carbide with a metal matrix, such as cobalt, to improve wear resistance and toughness. • WC-Ni (Tungsten Carbide-Nickel): Another composite coating, this provides improved wear resistance while offering better toughness than pure tungsten carbide. Other Alloy Materials • Copper alloys: Coatings made from copper and its alloys can improve electrical conductivity and corro sion resistance. Examples: Bronze, brass.

Common applications of HVOF coatings • Aerospace: Protection of turbine blades, compressor blades and other engine components. • Oil and gas: Coatings for drill bits, pumps and valves exposed to extreme abrasion and corrosion. • Automotive: Coatings on engine components to improve wear resistance and protect against corrosion. • Mining and cement: Coatings for tools and equipment exposed to high abrasion. Considerations for HVOF Coating Materials • Adhesion strength: The material must bond well with the substrate. • Wear resistance: The material chosen should be able to withstand abrasive and erosive environments. • Thermal properties: Some applications require mate rials with high resistance to heat and oxidation, such as in turbines. • Corrosion resistance: In environments where exposure to chemicals or saltwater is a concern, corrosion-resis tant materials like nickel alloys or stainless steels are often preferred. Choosing the right material for an HVOF coating is crucial for ensuring the coating meets the performance and dura bility requirements of the specific application.

• Molybdenum: Molybdenum coatings are used for high-temperature applications requiring strength and wear resistance.

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WINTER 2025

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