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Weld overlay is a surface modification process used to apply a corrosion-resistant or wear-resistant alloy onto a base metal through welding deposition techniques. This significantly improves the durability and performance of valves used in extreme wear, corrosion, and high-temperature applications.

Properties

Properties

  • Enhanced Corrosion Resistance – Protects against acidic, alkaline, and chloride-rich environments.
  • Superior Wear & Erosion Resistance – Prevents galling, abrasion, and erosion in high-friction applications.
  • Improved High-Temperature Performance – Withstands extreme temperatures in steam, refinery, and power plant systems.
  • Extends Service Life – Strengthens valve components while maintaining the mechanical properties of the base metal.
  • Cost-Effective Alternative to Solid Alloy Valves – Uses a thin layer of high-performance material, reducing overall material costs.

Weld Overlay vs. Other Surface Treatments
• More durable and corrosion-resistant than hard chrome plating or nitriding
• Stronger and thicker than thermal spray coatings (HVOF, plasma spray)
• More cost-effective than using full solid alloy valve components

Common Weld Overlay Materials Used in Valves
• Inconel (625, 825, 718) – High corrosion resistance for chemical and marine applications
• Stellite (Co-based alloy) – Excellent for wear, galling, and high-temperature resistance
• Hastelloy (C-22, C-276) – Used in severe chemical and acidic environments
• Chromium Carbide Overlay – Ideal for abrasion-resistant slurry and mining valves
• 316L Stainless Steel Overlay – Protects carbon steel valves from moderate corrosion

Limitations

Limitations

  • Higher Initial Cost – More expensive than basic coatings or plating, but cost-effective in the long run.
  • Heat-Affected Zone (HAZ) Risk – Can alter base metal properties if not properly controlled.
  • Requires Skilled Welding Procedures – Needs precise welding techniques (e.g., GTAW, PTAW, or laser cladding) to ensure quality.

Common Applications

Common Applications

Oil & Gas Valves – Protects against sour gas, CO₂, and H₂S-induced corrosion.
Chemical Processing Valves – Handles exposure to acidic and caustic chemicals.
Power Plant & Steam Valves – Withstands high-pressure, high-temperature steam and thermal cycling.
Mining & Slurry Valves – Provides superior abrasion and impact resistance.
Marine & Offshore Valves – Resists saltwater corrosion in subsea applications.