Question

Surface Hardening
a. Define and explain difference between through hardening and surface hardening.
b. Outline major steps involved in the carburizing process.
c. List TWO phases that can be observed in plain carbon steel that has been cooled very slowly to room
temperature from red hot state. Assume that steel contains 0.2Wt% Carbon (Hint: Iron-Iron Carbide
equilibrium Phase diagram).
d. What is difference amongst face centred cubic (FCC), Body Centred cubic (BCC) and Body centred tetragonal
(BCT) in terms of their crystal structure. Draw sketches.
e. Define austenitization.
f. In relation to plain carbon steel; identify TWO major factors that promote formation of martensite.
g. List THREE major strengthening processes that can be applied to strengthen metallic materials.
h. Study the Fe-Fe3C equilibrium phase diagram, and identify the phase(s) that occurs plain carbon steel
having a carbon content of 0.8% by weight at (1) Room Temperature, (2) 1000 degree Celsius
i. List three variants of carburizing process, and describe them briefly.
j. Define induction hardening, and identify comparative advantage of using induction hardening over
traditional hardening process.
k. Alpha ferrite, austenite, bainite and martensite are phases that occur in ferrous alloys; which phase is the
hardest? And which phase is the softest?
l. What is effect of increasing carbon content in steel on its hardness?
m. What is difference between nitriding and carbonitriding?

6. Cladding:
a. Define cladding, and outline major steps involved in the cladding process.
b. List at least TWO industrial applications of cladding.
c. Explain how cladding is different from thermal spray coating process.
d. What is a difference between fusion welding and solid state welding, and identify at least one process in
each case.

Answer 1