Engineering Materials

Question 1 of 12

Original Exam: GATE (2025)

Among the following surface-hardening processes, in which process is steel heated to the lowest temperature?

A. Carburizing B. Cyaniding C. Nitriding D. Carbonitriding

✓ Correct Answer: C

Explanation:
Correct answer: C, nitriding. Nitriding is carried out at about 500–550 °C, lower than the typical temperatures used for carburizing, cyaniding and carbonitriding. Traceable to GATE ME 2025 Set 1 Q20; verified against the GATE 2025 final answer key.

Difficulty: intermediate Type: conceptual

Question 2 of 12

Original Exam: GATE (2024)

The phases present in pearlite are:

A. Austenite and ferrite B. Cementite and austenite C. Ferrite and cementite D. Martensite and ferrite

✓ Correct Answer: C

Explanation:
Pearlite is the eutectoid microconstituent consisting of ferrite (α) and cementite (Fe3C). Traceable to GATE ME 2024 Set 1 Q28. The official GATE 2024 master answer key gives option C.

Difficulty: basic Type: conceptual

Question 3 of 12

Original Exam: GATE (2021)

The cast iron in which essentially all carbon is present in the combined form as cementite is called:

A. Grey cast iron B. Spheroidal graphite cast iron C. Malleable cast iron D. White cast iron

✓ Correct Answer: D

Explanation:
White cast iron contains carbon predominantly as cementite (Fe3C), giving it high hardness and brittleness. Traceable to GATE ME 2021 Set 2 Q14.

Difficulty: basic Type: conceptual

Question 4 of 12

Original Exam: GATE (2020)

Which crystal structure does γ-iron (austenite) possess?

A. BCC B. FCC C. HCP D. BCT

✓ Correct Answer: B

Explanation:
γ-iron (austenite) has a face-centered cubic (FCC) crystal structure. α-iron (ferrite) is BCC at lower temperatures. Traceable to GATE ME 2020 Set 1 Q20.

Difficulty: basic Type: conceptual

Question 5 of 12

Original Exam: GATE (2020)

Match the heat-treatment process with its principal effect: P-Tempering, Q-Quenching, R-Annealing, S-Normalizing; 1-Strengthening, 2-Toughening, 3-Hardening, 4-Softening.

A. P-2, Q-3, R-4, S-1 B. P-1, Q-1, R-3, S-2 C. P-3, Q-3, R-1, S-3 D. P-4, Q-3, R-2, S-1

✓ Correct Answer: A

Explanation:
Tempering mainly increases toughness; quenching produces hard martensite; annealing softens the steel; normalizing refines grains and improves strength. Hence A. Traceable to GATE ME 2020 Set 1 Q21.

Difficulty: intermediate Type: conceptual

Question 6 of 12

Original Exam: GATE (2020)

Which statement about an equilibrium phase diagram is INCORRECT?

A. It indicates temperatures at which phases start to melt. B. It can be used to determine relative phase amounts at equilibrium. C. It provides information about transformation rates. D. It depicts solid-solubility limits.

✓ Correct Answer: C

Explanation:
An equilibrium phase diagram describes stable phases and phase amounts, but not transformation kinetics or rates. TTT/CCT diagrams provide kinetic information. Traceable to GATE ME 2020 Set 2 Q21.

Difficulty: basic Type: conceptual

Question 7 of 12

Original Exam: GATE (2019)

Hardenability of steel is a measure of:

A. Ability to harden during cold working B. Maximum hardness after austenitizing and quenching C. Depth to which the required hardness is obtained after austenitizing and quenching D. Ability to retain hardness at elevated temperature

✓ Correct Answer: C

Explanation:
Hardenability describes how deeply a steel can be hardened to a specified hardness after austenitizing and quenching; it is not the same as maximum surface hardness. Traceable to GATE ME 2019 Set 3 Q14.

Difficulty: basic Type: conceptual

Question 8 of 12

Original Exam: GATE (2017)

For mild steel, the ultimate tensile strength (UTS) on the engineering stress-strain curve corresponds to the:

A. Yield stress B. Proportional limit C. Maximum stress D. Fracture stress

✓ Correct Answer: C

Explanation:
UTS is the maximum engineering stress reached on the tensile stress-strain curve before necking causes the engineering stress to decrease. Traceable to GATE ME 2017 Set 1 Q25.

Difficulty: basic Type: conceptual

Question 9 of 12

Original Exam: GATE (2016)

The Jominy end-quench test is used to determine:

A. Young's modulus B. Hardenability C. Yield strength D. Thermal conductivity

✓ Correct Answer: B

Explanation:
The Jominy end-quench test measures the variation of hardness along a quenched specimen and is therefore a standard test for steel hardenability. Traceable to GATE ME 2016 Set 1 Q30.

Difficulty: basic Type: conceptual

Question 10 of 12

Original Exam: GATE (2015)

The strain-hardening exponent n of stainless steel SS 304 undergoing plastic deformation with distinct yield and UTS values lies in which range?

A. n < 0 B. n = 0 C. 0 < n < 1 D. n = 1

✓ Correct Answer: C

Explanation:
For strain-hardening metals described by the Hollomon relation σ = Kε^n, the strain-hardening exponent is positive and less than 1. Hence 0 < n < 1. Traceable to GATE ME 2015 Set 3 Q15.

Difficulty: basic Type: conceptual

Question 11 of 12

Original Exam: GATE (2014)

For medium-carbon steel, match the heat-treatment processes with their effects: P-Tempering, Q-Quenching, R-Annealing, S-Normalizing; I-Strengthening and grain refinement, II-Inducing toughness, III-Hardening, IV-Softening.

A. P-III, Q-IV, R-II, S-I B. P-II, Q-III, R-IV, S-I C. P-III, Q-II, R-IV, S-I D. P-II, Q-III, R-I, S-IV

✓ Correct Answer: B

Explanation:
Tempering induces toughness (II), quenching hardens (III), annealing softens (IV), and normalizing provides strengthening and grain refinement (I). Hence B. Traceable to GATE ME 2014 Set 4 Q34.

Difficulty: intermediate Type: conceptual

Question 12 of 12

Original Exam: GATE (2022)

A plain-carbon steel contains 0.5 wt.% carbon. Using the Fe-Fe3C data CE = 0.8 wt.% C and Cα = 0.025 wt.% C, the fraction of pro-eutectoid ferrite after slow cooling to room temperature is approximately:

A. 0.387 B. 0.864 C. 0.475 D. 0.775

✓ Correct Answer: A

Explanation:
This is a faithful, self-contained paraphrase of GATE ME 2022 Set 1 Q41. For pro-eutectoid ferrite, Wα = (CE−C0)/(CE−Cα) = (0.8−0.5)/(0.8−0.025) = 0.3/0.775 ≈ 0.387. The published PYQ source gives option A. The original paper included the Fe-Fe3C diagram; the numerical values needed for the calculation are explicitly retained here, so no image is required for SSRAO import.

Difficulty: intermediate Type: numerical

Ferrous Materials