Black nitride combines nitriding with a post-oxidation step to produce a hardened diffusion layer together with a black surface oxide. The nitrided case improves wear resistance and fatigue behavior, while the post-oxidation layer contributes some additional corrosion resistance and dark appearance.
The hardening mechanism is nitrogen diffusion into the steel surface and formation of alloy nitrides in the diffusion zone.
Because the process occurs below the steel’s transformation temperature, it generally causes less distortion than carburizing or conventional hardening.
At Braddock, black nitride would be used when a component needs both a hard, low-friction surface and a dark oxide finish, particularly on finished or semi-finished alloy steel parts.
The process is commonly used on components where wear, sliding contact, and appearance all matter.
Parts are first nitrided, commonly in the approximate 925°F to 1050°F range, depending on alloy and process method. Nitrogen diffuses into the surface and forms a compound layer, along with a deeper diffusion zone. A post-oxidation step then produces the black finish.
Surface hardness and effective case depth depend on alloy composition, nitriding potential, process time, and prior core condition.
The process is most effective on steels containing nitride-forming elements such as chromium, molybdenum, vanadium, or aluminum.
Braddock would control nitriding temperature, time, atmosphere or salt chemistry, and post-oxidation practice because these variables determine compound layer thickness, case depth, hardness, and final appearance.
