Home / Materials
Materials and specifications
The process works on alloys that hold chromium in solid solution — which covers most of the corrosion-resistant materials you are likely to be machining. Here is the envelope, and the design rules that come with it.
Alloy families
Treatable materials.
Austenitic and duplex stainless steels are the core of the process. Nickel-based alloys, A286 and cobalt-chromium alloys respond as well. Martensitic and precipitation-hardened grades can be treated, but the process temperature must stay below the alloy’s tempering or ageing temperature so the bulk properties are not lost — which constrains the achievable case depth.
| Family | Representative grades | Response | Notes |
|---|---|---|---|
| Austenitic stainless | 304, 304L, 316, 316L, 321, 904L | Excellent | The reference case. Highest hardness gain and the deepest, most uniform diffusion zones. |
| Duplex and super-duplex | S31803, S32205, S32750, S32760 | Excellent | Both phases harden, though at different rates. Widely used for chloride and subsea service. |
| Nickel-based alloys | Inconel 600 / 625 / 718, Hastelloy C-276 | Very good | Effective on galling-prone nickel alloy sealing and threaded components. |
| Cobalt-chromium alloys | CoCrMo, Stellite grades | Very good | Common in medical and severe-wear service where an already hard alloy needs more. |
| Iron-based superalloys | A286 (UNS S66286) | Very good | Austenitic and precipitation strengthened. Treatment runs below its ageing temperature, so bulk strength is retained. A common choice for high-strength, galling-prone fasteners. |
| Precipitation hardened | 17-4 PH, 15-5 PH, 13-8 Mo | Good, constrained | Process temperature must remain below the ageing temperature for the supplied condition. Tell us the condition — H900, H1025, H1150 and so on. |
| Martensitic stainless | 410, 420, 440C, 430 | Good, constrained | Must stay below the tempering temperature, which limits case depth. Best where corrosion resistance must be preserved alongside existing bulk hardness. |
| Carbon and low-alloy steel | — | Not applicable | No chromium to protect and no expanded austenite to form. Conventional nitriding or carburizing is the correct answer here. |
Design and part preparation
What we need from your part before it goes in.
Diffusion happens at the actual metal surface. Nearly every disappointing result traces back to something on that surface or something done to the part afterwards.
- Finish machine first. The case is microns deep. Any machining, grinding or lapping after treatment removes it locally.
- Weld first. Welding after treatment destroys the case and the corrosion benefit in the heat-affected zone.
- Arrive unplated and unpassivated by third parties. Plating, anodic films, black oxide and heavy shot-peening layers all interfere with uniform diffusion.
- Send us the surface you want back. Roughness is preserved rather than improved, so treat surface finish as an input specification.
- Declare the supplied condition. Solution annealed, cold worked, aged — for PH and martensitic grades, the temper or ageing condition sets our temperature ceiling.
- Expect the whole part to be treated. Masking is not possible, so every surface is hardened. Finish all machining, threading and weld preps before treatment.
- Flag thin sections and springs. Very thin walls, foils and fine wire can be fully converted through-section, which changes bulk behaviour.
- Tell us the service temperature. Expanded austenite is metastable; sustained high service temperature is the one condition that can undo it.
Lead time
5–7days
Typical turnaround from receipt of parts to shipment, including verification.
- Day 0Parts received, inspected, cleaned and fixtured
- Days 1–5Low-and-slow NEXT-Phase™ cycle, with coupons in the load
- Days 5–7Coupon hardness and metallography checked, parts released and shipped
Part size and volume
From single prototypes to repeat production batches.
Parts are processed in batches on fixtures or in mesh baskets, with loading arranged so that gas reaches every surface that has to harden. Because the treatment is gaseous and diffusion driven rather than line of sight, bores, blind holes, internal passages, threads and undercuts harden along with the outside of the part.
We handle single-piece prototypes and trial coupons alongside repeat production. If you are evaluating the process, the practical starting point is a small trial lot of real parts — not test blanks — because geometry and surface condition are part of the result.
Typical lead time is 5–7 days. For envelope, load weight and a confirmed date on your specific part, send the drawing and quantity.