Stellite 4

1. Exceptional hardness and wear resistance: Typical hardness in cast or weld-deposited condition reaches up to HRC 48-56, with high content of hard carbides, providing far superior resistance to abrasive and adhesive wear compared to ordinary stainless steels and tool steels.
2. Excellent high-temperature hot hardness and oxidation resistance: It maintains considerable hardness at temperatures up to and above 760°C (1400°F), with hardness remaining around 35 HRC at 600°C. Its high chromium content imparts outstanding oxidation and thermal corrosion resistance.
3. Good corrosion resistance: It exhibits good corrosion resistance to various oxidizing acids (e.g., nitric acid), moderately concentrated non-oxidizing acids (e.g., ≤50% sulfuric acid), and alkaline solutions. In chloride media such as seawater, it primarily undergoes pitting corrosion rather than uniform mass loss.
4. Good impact resistance and self-lubrication (to a certain extent): Compared to hard materials like tungsten carbide of equivalent hardness, Stellite 4 offers better impact and thermal shock resistance. During friction, an oxide layer with lubricating properties forms on its surface, effectively reducing the coefficient of friction and adhesive wear.
5. Suitable for various hardfacing processes: It can be hardfaced using methods such as PTA (Plasma Transferred Arc), TIG, and oxy-acetylene welding. Typical standards include AWS A5.21 ECoCr-C, AWS A5.13 ECoCr-C, and UNS R30004.

Stellite 4 is a cobalt-based wear-resistant alloy and typically does not undergo traditional precipitation hardening or aging treatments to alter hardness (its hardness primarily derives from the carbide structure in the as-cast condition). Its typical heat treatment specifications include annealing:
1. Annealing (for reducing hardness to facilitate machining): Heat to approximately 1100°C, hold for sufficient time (depending on section thickness), then furnace cool slowly to reduce hardness and facilitate limited machining.
2. Hardening (to restore hardness after hardfacing): If pre-annealed, subsequent hardening is required to restore wear resistance: Heat to approximately 1050°C, hold, then quench rapidly in air or oil.
Note: Stellite 4 is a brittle wear-resistant material, making it extremely difficult to machine. Final finishing must be done by grinding or Electrical Discharge Machining (EDM). Preheating to 300-600°C and controlling interpass temperature during hardfacing, followed by slow cooling after welding, are necessary to avoid hot cracking.

Continuous operating temperature (primarily for wear and oxidation resistance): Recommended ≤ 760°C (1400°F), where it maintains hot hardness and microstructural stability. Even if softened in the 600-800°C range, its hardness remains far higher than most iron-based alloys (e.g., tool steels), fully meeting performance requirements for medium-to-high temperature wear parts.
Short-term exposure temperature: Can reach up to 870°C (approximately 1600°F), but attention should be paid to the degree of hardness reduction.
Pressure-bearing conditions: Due to its brittleness and relatively low tensile strength (approximately 550-900 MPa), Stellite 4 is generally not recommended as a structural material for components subjected to high tensile loads. When used for cladding or hardfacing, the base structure should be designed in accordance with relevant standards.

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