The process where the carbon from outside is introduced in the surface of steel by keeping charcoal at higher temperatures is called ________. 

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NHPC JE Mechanical 6 April 2022 (Shift 1) Official Paper
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  1. nitriding
  2. tempering
  3. case hardening
  4. quenching

Answer (Detailed Solution Below)

Option 3 : case hardening
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Explanation:

Case Hardening:

Case hardening is a method used to harden the outer surface of low-carbon steel while leaving the center or core soft and ductile.

Case hardening involves heating the metal to its critical temperature in some carbonaceous material.

The following methods are commonly used:

  1. Carburizing
  2. Cyaniding
  3. Nitriding
  4. Induction Hardening
  5. Flame hardening

 

Nitriding:

In the nitriding process, the surface is enriched not with carbon, but with nitrogen. There are two systems in common use, gas nitriding, and salt bath nitriding.

The gas nitriding process consists of heating the parts at 500°C in a constant circulation of ammonia gas for up to 100 hours and cooling them in the air.

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