Tufftride®  (Salt Bath Ferritic Nitrocarburising)

  • Tufftride® (called TENNIFER in the USA and some other countries) imparts a thin iron carbo-nitride compound or white layer with some sub-surface nitrogen penetration.
  • In most nitrocarburising processes, and certainly ferritic processes, nitrogen penetration into the substrate is  limited, typically about 0.5mm, so whilst thin materials (1mm and less) will result in a substrate that is substantially nitrogen bearing, and thus with increased yield strength, thicker materials will not – in these thicker materials it is only the immediate sub-surface that benefits.
  • Ferritic Nitrocarburising is usually carried out between 550°C and 610°C with process times varying from less than one hour to three hours or more. 
  • The process is generally followed by a further intermediate cooling oxidation treatment (AB1®), typically held in the salt bath at around 400°C to give components an aesthetic black finish and improved corrosion resistance.
  • Quench, Polish, Quench (QPQ) consists of Ferritic Nitrocarburising followed by AB1, quench, air cool and wash then mechanical polishing, lapping or vibratory finishing and re-immersion into the oxidising AB1 salt bath. The end result gives a superb lustrous black finish with enhanced corrosion resistance.
  • Improved corrosion resistance.
  • Improved fatigue properties.
  • Minimal distortion caused by the process itself. In most cases no final machining is needed.
  • Improved wear and galling resistance, reduced coefficient of friction (good Tribolgical Properties)
  • Relatively short process cycle times, aids production planning and limits costs.
  • Increased surface hardness.
  • Improved aesthetic appearance.
  • Applicable to a very wide range of materials.
  • The Ferritic Nitrocarburising process produces a thin outer iron nitride compound layer, with a deeper nitrogen diffusion layer underneath.  The compound layer of composition is formed to a depth of 10µm – 20µm during average nitrocarburising times.  Due to its composition, the layer does not possess adverse properties, thus making it particularly resistant to wear, seizure, corrosion, hot cracks and in some base materials is durable almost to the temperature at which it was formed.
  • Identified as a surface treatment, it is used to improve the corrosion protection and service life of steel, sintered iron (metal) and cast iron components.
  • This treatment is mainly applied to carbon, low alloy steels, certain SG and cast irons, and copper alloys, 080M40 (EN8), 070M55 (EN9), 150M19 (EN14), 150M36 (EN15), 070M20 (EN3).
  • The two layers compound and diffusion contribute to improved wear, corrosion resistance and fatigue properties and because processing temperatures are below critical transformation temperatures for steel, distortion attributable to the process itself is extremely low.  Very often treatments whose aims are to increase one or two of these properties fail to achieve the third.  This improvement of all three properties is achievable from a single heat treatment.
  • Maximum size is 640mm diameter x 900 mm length (1200mm maximum length on double end immersion).  Weight up to 250Kg.

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
Email: info@keighleylabs.co.uk

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Service Type
Tufftride - Salt Bath Ferritic Nitrocarburising
Provider Name
Keighley Laboratories,
Croft House South Street,Keighley,West Yorkshire-BD21 1EG,
Telephone No.+44 (0)1535 664211
Keighley, United Kingdom
Tufftride® (called TENNIFER in the USA and some other countries) imparts a thin iron carbo-nitride compound or white layer with some sub-surface nitrogen penetration.