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Chemical Engineering Basics - Engineering

Q1:

Alloying elements present in Hayness stel-lite, which has superior performance than high speed steel, are

A nickel, cobalt & chromium.

B tungsten, chromium & cobalt.

C manganese, chromium & cobalt.

D tungsten, molybdenum & nickel.

ANS:B - tungsten, chromium & cobalt.

Tungsten (W):

    • Tungsten is a hard and dense metal known for its high melting point and exceptional hardness.
    • In Stellite alloys, tungsten is added primarily to enhance hardness and wear resistance. It forms hard carbides when combined with carbon during the alloying process.
    • Tungsten carbides dispersed throughout the alloy matrix provide abrasion resistance, making Stellite alloys highly resistant to wear and erosion, particularly in high-stress applications such as cutting tools and wear-resistant components.
  2. Chromium (Cr):
    • Chromium is a corrosion-resistant metal that forms stable oxide layers on its surface, providing protection against oxidation and corrosion.
    • In Stellite alloys, chromium contributes to both corrosion resistance and hardness. It forms chromium carbides when combined with carbon, which further enhances hardness and wear resistance.
    • Chromium also helps stabilize the microstructure of the alloy, improving its mechanical properties and thermal stability.
  3. Cobalt (Co):
    • Cobalt is the primary component of Stellite alloys, serving as the matrix metal that holds the alloy together.
    • Cobalt provides excellent strength, toughness, and ductility to Stellite alloys, making them highly durable and resistant to deformation under mechanical stress.
    • Cobalt also enhances the machinability of Stellite alloys, allowing them to be easily shaped and formed into complex components.
    • Additionally, cobalt improves the high-temperature properties of Stellite alloys, enabling them to maintain their mechanical strength and hardness at elevated temperatures.
In summary, tungsten, chromium, and cobalt are essential alloying elements in Stellite alloys, working together to provide superior hardness, wear resistance, corrosion resistance, and mechanical properties. These alloys are widely used in applications where durability, longevity, and performance under extreme conditions are critical, such as cutting tools, valve components, bearings, and aerospace components.