stellite

Stellite is a family of cobalt-based alloy systems renowned for hardness, wear resistance, and strength at high temperatures. Developed for hardfacing and industrial wear parts, Stellite grades are used in tools and components that operate under abrasive, corrosive, or thermal stress. The alloys are typically applied as protective weld overlays or surface coatings and, in some cases, fabricated as wrought materials.

Composition and variation: The base is cobalt, alloyed with chromium and carbide-forming elements such as tungsten, molybdenum, or vanadium. Carbon content is kept to form hard carbides that enhance wear resistance. The exact composition varies by grade, with common designations such as Stellite 6 and Stellite 21 representing different carbide contents and balance of ductility versus hardness. Some grades include nickel to improve toughness or corrosion resistance.

Properties: Stellite alloys exhibit high hardness, typically through carbide precipitation, and retain strength at elevated temperatures. They offer excellent wear and abrasion resistance and good corrosion resistance in many environments. They are typically not highly ductile and can be challenging to machine; application as hardfacing is performed by welding, brazing, or thermal spraying to produce a hard surface while maintaining a tougher substrate.

Applications: They are widely used for valve seats, valve stems, pump impellers, bearing surfaces, cutters and mining tools, and turbine blades where wear resistance is critical. They are also used in other components subject to abrasion and high-temperature service, such as aerospace hardware and industrial machinery.

History: Stellite originated as a brand-name cobalt-based alloy developed in the early 20th century for industrial wear applications. It became associated with hardfacing and is now used generically to describe cobalt-chromium carbide alloys produced by several manufacturers.