Case hardening basics: Nitrocarburizing vs. carbonitriding
It’s easy to get lost in the chemistry—and the nomenclature—behind heat-treating processes. There’s peace of mind in knowing what processes your parts will undergo, but only if you understand them.…
Carbonitriding
Carbonitriding is an austenitic (above A3) case hardening process similar to carburising, with the addition of nitrogen (via NH3 gas), used to increase wear resistance and surface hardness through the creation…
Nitriding
Large gear for an industrial application nitrided to a 0.040" case depth. Gear measures 12' in diameter by 12' tall and weighs approximately 24,000 pounds. Gear hub, bore and web…
Carburizing
Carburizing Heat Treatment for Machined Gears, Machined Parts and StampingsCarburizing steel produces a hard, carbon-rich case on the outer surface of the heat-treated components, while the core of the part…
What Is Case Hardening
Case hardening is a technique in which the metal surface is reinforced by the adding of a fine layer at the top of another metal alloy that is generally more…
Martempering/Marquenching
Marquenching/Martempering is a form of heat treatment applied as an interrupted quench of steels typically in a molten salt bath at a temperature right above the martensite start temperature. The…
Austempering
Austempering is a heat treating process for medium-to-high carbon ferrous metals which produces a metallurgical structure called bainite. It is used to increase strength, toughness, and reduce distortion. Parts are…
Continuous Cooling Transformation Diagrams
In the last column, we discussed the construction and application of Time Temperature Transformation or Isothermal Transformation diagrams. It was shown how these diagrams could be used to start planning…
I-T Diagram and Cooling Curves
Phase Diagrams are limited in their usefulness because they can only predict the microstructure that will result for equilibrium conditions, i.e. very very slow cooling. Non-equilibrium cooling will result in…
MARTEMPERING AND AUSTEMPERING
It will be readily appreciated that the quenching operation used in hardening introduces internal stresses into the steel. These can be sufficiently large to distort or even crack the steel.…
