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Surface hardening techniques, such as case hardening and induction hardening, are often used as heat treatment processes for drive and transmission systems - Leaving Cert Engineering - Question c - 2017
Question c
Surface hardening techniques, such as case hardening and induction hardening, are often used as heat treatment processes for drive and transmission systems. (i) Out... show full transcript
Worked Solution & Example Answer:Surface hardening techniques, such as case hardening and induction hardening, are often used as heat treatment processes for drive and transmission systems - Leaving Cert Engineering - Question c - 2017
Step 1
Outline two reasons for surface hardening the teeth of the gear wheels.
Answer
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Prolongs lifespan: Surface hardening increases the wear resistance of the gear teeth, thereby prolonging their lifespan as they will not wear down as easily during operation.
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Maintains shape: The process allows for the outer layer of the gears to be harder, while the inner layers remain softer and more ductile, ensuring that the gear teeth maintain their shape and structural integrity over time.
Step 2
Describe a case hardening process.
Answer
Case hardening is a heat treatment process that involves packing the component in a material rich in carbon, such as charcoal. The following steps detail the pack method of case hardening:
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Preparation: The piece to be carburised is sealed in a container with activated charcoal and placed in a furnace.
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Heating: The furnace is heated to approximately 920°C (above UCT), which allows the carbon to diffuse into the surface of the piece.
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Diffusion: The duration in the furnace influences the depth of carbon penetration. The longer the duration, the deeper the carbon penetration becomes, resulting in a hard outer shell.
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Quenching: To avoid cracking, after heating, the component is quenched in a bath of molten salt at about 780°C for half an hour, which solidifies the carburised layer.