Engineering Materials

Choose the correct option:

Which of the following is the hardest?

(i) Austenite
(ii) Bainite
(iii) Pearlite
(iv) Martensite

Choose the correct option:

Carbon and Nitrogen are introduced into the surface of steel during

(i) Normalizing
(ii) Cyaniding
(iii) Hardening
(iv) Tempering

Choose the correct option:

The main purpose of normalising a hypoeutectoid steel is to:

(i) Produce very soft coarse pearlite for maximum ductility only
(ii) Refine grain size and produce uniform fine pearlite for improved strength and toughness
(iii) Form martensite for maximum hardness
(iv) Produce spheroidised cementite for easy machining

Choose the correct option:

Identify the correct statement regarding case hardening/surface hardening processes:

(i) Harden only high-carbon steels by through hardening
(ii) Modify the surface composition by diffusion of carbon and/or nitrogen while keeping a tougher core
(iii) Rely only in rapid quenching with no change in composition
(iv) Use only flame or induction as heat sources

Name the important heat treatment processes of steel. Explain any two of them with neat sketches.

Describe the factors promoting grain size of steel. What are the effects of grain size on mechanical properties?

Define annealing, normalising, tempering and spheroidising of steel, stating the typical heating temperature range relative to critical temperatures, holding, and cooling conditions.

Sketch and label a typical isothermal transformation (TTT) diagram for eutectoid steel.

Discuss the method of getting a mixture of Pearlite, Bainite & Martensite steel with a neat TTT diagram.

Explain the difference between a Time-Temperature-Transformation (TTT) diagram and a Continuous Cooling Transformation (CCT) diagram for steels.

Describe how to use TTT and CCT diagrams to predict the final microstructure and hardness for different cooling paths.

Explain the following: Case Hardening

Write a short note on: Surface hardening