NPTEL Online Certification Courses
Indian Institute of Technology Kharagpur
Jan 2025
Course Name: Surface Engineering for Corrosion and Wear Resistance Application
Assignment 6 - Week 6 (Jan 2025)
TYPE OF QUESTION: MCQ/MSQ
Number of questions: 15 Total mark: 15 X 1 = 15
QUESTION 1:
The principal reason for improving hardness and wear resistance of steel by nitriding is:
a. Solid solution strengthening
b. Martensite strengthening
c. Precipitation of incoherent nitrides
d. Precipitation of coherent nitrides
Correct Answer: c
Reference: Page 1 of L27
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QUESTION 2:
Nitriding is applicable to:
a. Low carbon alloy steel containing strong nitride former
b. Copper alloys
c. Only mild steel
d. Aluminum alloys
Correct Answer: a
Reference: Page 6 of L17
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NPTEL Online Certification Courses
Indian Institute of Technology Kharagpur
Jan 2025
QUESTION 3:
White layer formed on nitrided surface is called ‘white’ because:
a. Nitrides are too hard
b. Nitrides do not easily etch
c. Nitrides easily etch and appear bright
d. Iron nitrides are white in color
Correct Answer: b
Reference: Page 4 of L27
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QUESTION 4:
Typical hardness of nitride layer in Rockwell C scale can be:
a. Rc 40-50
b. Rc 55-70
c. Rc 10-20
d. Rc 20-30
Correct Answer: b
Reference: Page 7 of Lecture 27
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QUESTION 5:
Main advantage of plasma nitriding over gas nitriding is:
a. White payer consists of only one nitride compound
b. No vacuum pump is required
c. No need of using ammonia gas
d. Cooling rate after nitriding is faster
NPTEL Online Certification Courses
Indian Institute of Technology Kharagpur
Jan 2025
Correct Answer: c
Reference: Page 5 of Lecture 29
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QUESTION 6:
The temperature range of nitriding for steel-based component typically is:
a. 800-900 0C
b. 300-400 0C
c. 500-560 0C
d. 1000-1100 0C
Correct Answer: c
Reference: Page 3 of Lecture 27
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QUESTION 7:
Identify the correct statement while comparing gas nitriding with plasma nitriding:
a. The phase aggregate is the same
b. The reaction kinetics are the same
c. The precursor gas mixture is the same
d. The nitriding time (for identical depth) is the same
Correct Answer: a
Reference: Page 5 of Lecture 29
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NPTEL Online Certification Courses
Indian Institute of Technology Kharagpur
Jan 2025
QUESTION 8:
Usually, the first nitride to form during nitriding at the surface of a steel component is:
a. Fe4N
b. Fe2N
c. Fe2-3N
d. FeN
Correct Answer: a
Reference: Page 3 of Lecture 27
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QUESTION 9:
In salt bath nitriding, the nitrogen donating medium is a nitrogen-containing soluble compound such as
a. Cyanide
b. Carbide
c. Sodium Chloride
d. None of the above
Correct Answer: a
Reference: Page 3 of Lecture 28
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QUESTION 10:
The primary advantage of salt bath nitriding over gas nitriding is:
a. It results in a deeper hardening layer
b. It can be performed at higher temperatures
c. It does not require quenching after the process
d. It provides a more uniform nitrogen distribution
NPTEL Online Certification Courses
Indian Institute of Technology Kharagpur
Jan 2025
Correct Answer: d
Reference: Page 3 of Lecture 28
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QUESTION 11:
The ion implantation depth in Plasma Immersion Ion Implantation (PIII) is controlled by:
a. The material's grain size
b. The voltage applied to the material and the ion species used
c. The temperature of the material
d. The time the material is exposed to the plasma
Correct Answer: b
Reference: Page 3 of Lecture 18
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QUESTION 12:
Which of the following is typically used as a precursor gas for the plasma nitriding process?
a. Ammonia (NH₃)
b. Oxygen (O₂)
c. Methane (CH₄)
d. Nitrogen (N₂) and hydrogen (H₂) mixtures
Correct Answer: d
Reference: Page 4 of Lecture 29
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NPTEL Online Certification Courses
Indian Institute of Technology Kharagpur
Jan 2025
QUESTION 13:
In plasma nitriding, the rate of nitrogen diffusion into the surface is primarily controlled by:
a. The pressure of the gas mixture
b. The temperature of the plasma
c. The applied voltage to generate the plasma
d. The duration of the treatment
Correct Answer: b
Reference: Page 4 of Lecture 29
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QUESTION 14:
Why is it essential to heat-treat hardened steel?
a. To restore toughness
b. To increase hardness
c. To increase wear resistance
d. To increase corrosion resistance
Correct Answer: a
Reference: Page 4 of Lecture 30
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QUESTION 15
Which of the following is NOT a typical application for liquid bath nitriding?
a. Improving the wear resistance of high-performance gears
b. Increasing the surface hardness of valve components
c. Enhancing the corrosion resistance of stainless steel
d. Increasing the hardness of tool steels
NPTEL Online Certification Courses
Indian Institute of Technology Kharagpur
Jan 2025
Correct Answer: c
Reference: Page 1 of Lecture 28
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