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GATE 2025 ME – Question 20

Engineering Materials · Phase diagrams and heat treatment · 1 mark · Multiple choice

Among the following surface hardening processes, steel is heated to the lowest temperature in

  1. carburizing
  2. cyaniding
  3. nitriding
  4. carbonitriding

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Show answer and explanation

Correct answer: (C) nitriding

Explanation

Carburizing, cyaniding and carbonitriding all heat the steel to about 800 to 950 °C. Nitriding is done at a much lower temperature, about 500 to 550 °C, below the transformation range of the steel.