Gaseous Nitriding / Annealing

  • Gas Nitriding at Keighley Laboratories Limited is a low temperature, low distortion thermo-chemical heat treatment carried out in vertical pit furnaces employing state of the art process controls.
  • The process is carried out in a sealed retort furnace in a flowing cracked ammonia atmosphere promoting diffusion of nitrogen into the surface. Cycles range between 12 and 120 hours allowing flexibility for customer demands.  A typical process temperature is 490°C to 525°C for standard processes.
  • Gas Nitriding is usually carried out on hardened and tempered components (fully stabilised) to produce a hard wear resistant case, enhanced corrosion resistance and improved fatigue strength.
  • Low temperature processing results in minimal dimensional changes.
  • Improved fatigue strength.
  • Usually performed on finished components, improving lead time.
  • Increased surface hardness promotes high resistance to wear, scuffing, galling and seizure.
  • Can improve corrosion resistance in some materials.
  • Versatility of the cycle ensures predictable metallurgical results through a range of total case depths ranging from 0.1mm up to the more traditional 0.7mm depth, however this is material dependent.
  • There are a number of true nitriding steels containing specific nitride forming elements, such as Aluminium, Chromium, Molybdenum and Vanadium. These materials include 722M24 (EN40B), 905M39 (EN41B) and 897M39 (EN40C).
  • Can include unalloyed or lean alloyed steels and other tool steels (hot/cold work and mould steels) such as 709M40 (EN19) and 817M40 (EN24).
  • Some stainless steels can produce very high surface hardness values exceeding 1000 HV though this is usually accompanied by a reduction in corrosion resistance.
  • It is important to note that whilst the process itself is inherently of a low distortion type, residual stresses remnant from component manufacture may cause distortion due to partial relief of these stresses in gas nitriding. It is recommended that components be interstage stabilised before machining to final size.
  • Components up to 940mm diameter and 1500mm long can be treated vertically using special jigging.  Weight up to 1000Kg.

James Menzies


Leonard Powell

Technical Planner

David Wright

Production Director

Keighley Laboratories Ltd
Registered Office:
Croft House
South Street
West Yorkshire
BD21 1EG
Registered in England 164811
UK Tel: +44 (0)1535 664211

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