Hardenability Flashcards
Define hardenability
A measure of how easily a material can be hardened, tested using jominy end quench test
How is the jominy end quench test preformed
- specimen is heated then quenching at one end, at a steady rate using a water jet
- the side is faced a little bit to garner an even surface
- hardness test are preformed along the side on the specimen
When is quenching in oil necessary over using water
Quenching high carbon steels water cools the material down too fast leading to warping and cracking
Name different hardening methods
- carburising
- nitriding
- flame
- shot peening
- burnishing
- hard coating
Define carburising
The chemical process of diffusing carbon into the surface of the material, done through liquid gas or solid environments. Quench in oil
- solid heated in charcoal powder, cheap but inefficient
- liquid heated in cyanide, efficient and less labour intensive but poisonous
- gas expensive set up but good for mass production
Applications of carburising
- low carbon steels
- improved resistance to wear
- shafts, gear, armoured plates, etc
Explain nitriding/boronizing
The chemical process of diffusing nitrogen/boron into the surface of the part, which forms nitrides. These cause block dislocations increasing hardness.
Explain flame hardening
Thermal process, that hardens the surface of high carbon steels by localised heat and quenching at high cooling rates
Explain induction hardening
A thermal process that uses local heating by inducing eddy currents, varying frequencies alters case depths
- parts have good impact resistance
Explain shot peening
The mechanical process of shooting steel balling towards the surfaces, creating local compressive stresses.
- useful for springs, shafts, turbine part, etc
Explain burnishing
The mechanical process of work hardening a piece by rolling the surface to smooth it, creating compressive residual stresses.
- used for seals, valves, spindles, tubes, etc
Explain explosive hardening
The mechanical process of detonating explosives on the surface, plastically deforming it
- used for railways
Explain hard coating
The process of coating the surface by welding, electroplating, ceramic plating, etc
