Gas Carburizing
Gas carburizing is a case-hardening heat treatment in which low-carbon steel is heated into the austenitic range within a carbon-rich gas atmosphere, causing carbon to diffuse into the surface. The part is then quenched and tempered to form a hard martensitic case over a tough, ductile core.
On a CNC manufacturing floor, gas carburizing is applied to gears, shafts, and other high-production components that need a wear-resistant surface but a shock-tolerant core. The typical workflow starts with machining the part oversize to accommodate heat-treat movement, followed by thorough cleaning and careful loading with controlled spacing. Carburizing then occurs in a regulated furnace atmosphere at roughly 850–950°C, where carbon potential, time, and temperature are adjusted for a targeted case depth. After quenching and tempering, only critical features are finish-machined. This process is valued for producing repeatable hardness and case depth, but it is not a cosmetic step. Thermal cycling introduces distortion, growth or shrinkage variability, and oxidation risks, so any critical bores, bearing journals, or tooth geometry are planned around post-heat-treat grinding or finish machining.
Why use gas carburizing instead of through-hardening?
Gas carburizing is chosen when the design needs a hard, wear-resistant skin combined with a ductile, shock-resistant core, rather than hardness throughout the full section.
What materials are most suitable?
Low-carbon steels and case-hardening steels are primarily used because they can absorb carbon effectively at elevated temperature and then transform to martensite on quenching.
Why is atmosphere control so important?
The carbon potential of the furnace atmosphere directly governs how much carbon enters the steel surface. Poor control changes case depth, hardness, and repeatability, causing inconsistent performance.