We case-harden stainless steels and nickel alloys by diffusing carbon into the surface at low temperature — forming a carbon-supersaturated case that exceeds 1000 HV without the chromium depletion of conventional nitriding, and without the distortion of high-temperature treatments.
304 SS · hex-flange bolt · treated
Low-temperature gaseous carburizing diffuses carbon interstitially into the alloy surface — no coating, no interface to spall, no line-of-sight limitation. On austenitic grades the result is expanded austenite: the γ lattice, swollen with carbon far beyond its equilibrium solubility.
Colossal carbon supersaturation strains the lattice and drives surface hardness from ~200–400 HV to well above 1000 HV — a several-fold increase in wear, galling, and erosion resistance. Because the case is diffused, not deposited, hardness grades smoothly into the substrate with no interface to delaminate.
The treatment runs below the temperature where chromium carbides precipitate. Chromium remains dissolved in the matrix — so the passive layer, and the corrosion resistance you specified the alloy for, is preserved. Many nitriding treatments can't make that claim: CrN formation strips chromium from solution and degrades corrosion performance.
No quench, no bulk phase transformation, and process temperatures a fraction of conventional carburizing mean negligible dimensional change. Threads, sealing surfaces, and precision bores come out to the same print they went in on — critical for finished components treated as a final step.
Nitriding can deliver hardness on stainless — but often at the cost of the stainless. Where chromium nitrides form, chromium leaves solution and pitting resistance drops. Low-temperature carburizing hardens the surface while leaving the alloy chemistry — and its passive film — alone. It also adds a layer of compressive residual stress, which benefits fatigue performance.
Every claim below is a measurement from a treated production part — not a lab coupon. Microhardness traverses, metallographic sections, and case-depth verification come standard with trial work.
Microhardness profile — 304 stainless self-tapping screw. Peak hardness ≈ 1180 HV0.01 near the surface, grading continuously to the substrate over ~35 µm. No step, no interface — a diffused case, not a coating.
316 stainless, etched cross-section. The carburized case (35.25 µm, measured) resists the etch and appears as a bright, uniform band above the austenite grain structure — visual confirmation that chromium hasn't been pulled into carbides.
Thread of the 304 hex-flange bolt from Fig. 00. The case (bright rim) follows the full thread profile — crest, flank, and root — with uniform depth. Gas-phase diffusion reaches every surface, including internal geometry.
The list above is what we've validated so far, not the limit of the process. If your grade isn't on it, we'd genuinely like to run it. Send us your material — or a few sacrificial parts — and we'll return a treated sample with a hardness traverse and metallographic section, at no obligation.
Stainless fasteners gall; carbon-steel ones rust. A hardened 304 or 316 fastener resists thread galling and seizure while keeping full corrosion resistance in salt spray and splash zones.
Ferrules and fitting bodies need a hardness differential to bite and seal reliably. A hardened case delivers it without switching alloys or plating — and without changing the fit-up dimensions.
Rotating and sliding stainless components in chemical, food, and water service — where wear debris, galling, and erosion end service life long before corrosion would.
Implant failures are frequently surface failures: fretting, wear debris, and the biological response they trigger. A hard, diffused, carbide-free case addresses wear without a coating that can shed particles.
A hardened stainless surface as an alternative to hard-chrome plating — no plating bath chemistry, no coating to chip at cutting edges, and full compatibility with repeated sterilization.
Nickel superalloys like IN718 are specified for strength at temperature — but they wear and fret. Case-hardening the surface extends life in fasteners, bushings, and mating hardware.
Where 410/416/420/440C components face abrasive wear and corrosive exposure — small arms, actuation, and marine defense hardware — a hardened case adds durability without a coating or dimensional change.
Tell us about your material and application — listed or not. Trial treatments return with a microhardness traverse and metallographic section so your engineers can judge the results directly.