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Ni-Hard is a type of white cast iron alloyed with nickel and chromium, known for its exceptional hardness, wear resistance, and moderate corrosion resistance. It is a proven, cost-effective material for valve components operating in abrasive environments where long wear life is essential and corrosion resistance is a secondary concern such as slurry handling, mining, and power generation.
Properties
- Exceptional Abrasion Resistance – Ideal for handling slurries, tailings, and particulate-laden fluids.
- High Hardness – Typically 450–600 HB, depending on grade and heat treatment.
- Moderate Impact Resistance – Better than some white irons, suitable for non-fragile erosion environments.
- Good Service Life – Used where long wear life is prioritized over ductility or corrosion resistance.
Ni-Hard vs. Other Hard Alloys
• Less corrosion-resistant and lower impact toughness than Stellite, but more economical
• Tungsten carbide provides superior hardness and wear resistance, but is more brittle and significantly more expensive than Ni-Hard
• Strikes a cost-effective balance for abrasion-focused applications where corrosion and impact resistance are less critical
There are several grades (e.g., Ni-Hard 1, 2, 4) with varying nickel (3–5%) and chromium (1.5–4.5%) content, optimized for different wear mechanisms (abrasion, impact, corrosion).
Limitations
- Low Ductility – Can be brittle, making it susceptible to cracking under high mechanical shock or thermal cycling.
- Limited Corrosion Resistance – Not suitable for acidic or corrosive fluid service; best used in wear-dominant applications.
- Challenging to Machine – Typically requires grinding rather than conventional machining.
Common Applications
Knife Gate & Slurry Valves – Seats, gate plates, and liners in mining and mineral processing.
Ash Handling & Power Plant Valves – Components in bottom ash, fly ash, and coal slurry systems.
Cement & Aggregate Valves – Applied in abrasive dry bulk handling.