Stellite 1

Stellite 1 achieves extensive M₇C₃ and M₆C type hard carbides (with hardness up to 1500-1800 HV) through its 'high carbon, high chromium, high tungsten' composition design, which are uniformly distributed within a cobalt-based solid solution matrix. This 'hard particle + tough matrix' composite structure enables it to effectively resist cutting and adhesive wear by abrasive particles. Typical hardness ranges for cast or weld-deposited conditions are between HRC 50-60 (approximately HV 550-720). Under dry friction conditions, its wear rate against quenched steel is only 1/20 that of 304 stainless steel and 1/5 that of weld overlay wear-resistant steels (e.g., D517). Even at temperatures above 400°C, its wear resistance degradation remains below 15%, far outperforming iron-based wear-resistant alloys (degradation >50%).

Stellite 1 is distinguished by its superior high-temperature hot hardness, maintaining considerable hardness even above 760°C (1400°F)-retaining approximately 37 HRC at 600°C and about 28 HRC at 870°C (1600°F). This outstanding property stems from the allotropic transformation of cobalt from hexagonal close-packed (ε-Co) to face-centered cubic (γ-Co) above room temperature, along with solid-solution strengthening provided by tungsten. In oxidizing atmospheres, the high chromium content promotes the formation of a dense Cr₂O₃ oxide film on the surface; after exposure to air at 800°C for 1000 hours, the oxidation weight gain is less than 1 mg/cm², offering better oxidation resistance than most iron-based heat-resistant steels. The alloy exhibits excellent microstructural stability during long-term service above 600°C, with no significant phase transformations or softening.

With approximately 30% chromium content and inherent properties of the cobalt matrix, Stellite 1 demonstrates good corrosion resistance in various corrosive media. At room temperature, it resists sulfuric acid concentrations up to 50%, hydrochloric acid up to 30%, and all concentrations of sodium hydroxide solutions, typically with corrosion rates below 0.1 mm/a. In oxidizing media such as nitric acid, its corrosion resistance even surpasses some nickel-based alloys. In seawater and chloride solutions, Stellite 1 primarily undergoes pitting rather than uniform mass loss, with a typical electrode potential of approximately -0.4 V (SCE). However, performance is limited in strongly reducing acids (e.g., hydrochloric acid) and fluorine-containing media. Additionally, the oxide film can be easily damaged under high-stress friction conditions, requiring the use of lubricants to maintain corrosion resistance.

Stellite 1 exhibits mechanical properties characterized by 'high hardness and low ductility': tensile strength at room temperature is approximately 550-1000 MPa, but elongation after fracture is only 1-3%, and impact energy (Charpy V-notch) is <10 J, classifying it as a typical wear-resistant brittle material. Therefore, it is unsuitable for applications subject to severe impact loads but performs exceptionally well in sliding wear and fretting wear conditions. The alloy is typically formed via precision casting or powder metallurgy. Weld overlay (PTA, TIG, oxy-acetylene) is the most common application method for Stellite 1. Due to its high susceptibility to hot cracking, preheating to 300-600°C and control of interpass temperature are required during welding, followed by slow cooling post-weld to reduce crack tendency. Because of its extremely high hardness, grinding or electrical discharge machining (EDM) are recommended for finishing operations.