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MEO Class II: MEKG MEKM MEP MET SC&S SSEP 📊 Trends
Q7 (16 Marks) Materials & Testing
MEKG • Written Exam

Explain EACH of the following metallurgical processes:

(a) Induction hardening (5)

(b) Nitriding (6)

(c) Case hardening (5)

Appeared In: Feb 2026

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Part (a)

Induction hardening is a process used for the surface hardening of steel and other alloy components. The parts to be heat treated are placed inside a copper coil and then heated above their transformation temperature by applying an alternating current to the coil. The alternating current in the coil induces an alternating magnetic field within the work piece which causes the outer surface of the part to heat to a temperature above the transformation range. By quenching this heated layer in water, oil, or a polymer based quench, the surface layer is altered to form a martensitic structure which is harder than the base metal.

Part (b)

Nitriding is a case-hardening process in which nitrogen is introduced into the surface of a ferrous alloy such as steel by holding the metal at a temperature below that at which the crystal structure begins to transform to austenite on heating. Nitriding is a diffusion-related surface treatment with the objective to increase surface hardness (among other properties) by the creation of a case on the surface of the part

Part (c)

Case hardening is a material processing technique by which the hardness of the outer surface of a metal is increased while keeping a soft ductile core. This process involves altering the crystal structure of the metal or chemical composition by adding new elements to the metal surface at elevated temperatures. This surface hardening method creates a thin layer of a wear-resistant, hard case which in turn increases the impact strength of the component as a whole. As with an increase in hardness the machinability usually reduces, the case hardening is performed at the final step after all other fabrication processes.

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