Ferritic nitrocarburizing

Teniferierung is a chemical / physical process to increase hardness of steel materials.

Method

The measures provided for treating objects are immersed depending on the steel composition and form from a few minutes to a few hours in a nitration with controlled cyanide - cyanate. The standard duration of treatment of 90 minutes at a temperature of 580 ° C. The Tenifer treatment is done on heat treated and made ​​machined workpiece. The final annealing temperature ( annealing = heat treatment to reduce the stress in the workpiece ) should be above the Tenifer treatment temperature of 580 ° C to ensure that no undesirable structural changes occur. Before treatment, the workpieces should be preheated slowly and thoroughly ( so that no stresses occur ) to about 350 ° C. After immersing follows in the Tenifer bath of 580 ° C. After reaching the maximum duration of treatment, the workpieces to be quenched in water, oil or in a polymer.

Furthermore, a subsequent re-oxidation has been proven ( Tenifer -Q method). Here the workpiece is immersed directly from the Tenifer bath in an AB1- bath at about 380 ° C and held for 10-15 minutes, making the surface is oxidized (black color) and at the same time adhering cyanide neutralized ( detoxification reaction). The adhering cyanide is converted into non-toxic sodium carbonate. Then follows a quenching in water.

An extension provides the Tenifer - QPQ process dar. QPQ stands for quenching - polishing - quenching. After the Tenifer treatment, the parts are oxidized in an oxidation bath (AB - bath) and then washed. As a substitute for a glass bead blasting, polishing is carried out in practice. The parts are then further oxidized in the AB1- bath for about 30 minutes, washed and dried. By cooling after the oxidizing treatment TUFFTRIDE the pores are filled with magnetite. Uniform oxidation layer 2-4 microns are typical and to be expected. Tenifer is a registered trademark of HEF Durferrit.

Properties

Dimensional change

Since during the Tenifer treatment occurs no structural transformation of the base material and the thermal stresses due to slow heating and cooling are very low, can be expected no significant dimensional changes. Only the compressive stresses occurring as a result of the nitride or carbo - nitride formation in the thin rim cause minor dimensional changes, however, are only of the order of 2-4 microns and limited to the marginal zone. Larger parts may, however, due to stresses in the surface of a certain delay.

Link layer

The connecting layer is formed in the storage of the nitrogen. When nitrogen retention in the edge region, the solubility is exceeded. By excreting iron nitrides a homogeneous, well- liable link layer forms. In the compound up to about 1000 HV hardening can occur.

Surface hardness

The surface hardness increases dramatically at the Tenifer treatment. The hardness in the nitrided zone and in the base material was measured with a Kleinlastprüfgerät Vickers ( diamond pyramid ) with a test load of 50 g. The maximum measurable hardness was 1150 HV 0.05 kg / mm ². (Limits Vickers 3 for lead and 1500 for ceramics ). For unalloyed steels ( S235JR2, C15, C45), the surface hardness is about 450 HV in quenched and tempered steels at 600-800 HV. In nitriding steels or high-alloy tool steels, the surface hardness may be more than 1000 HV. Nitride-forming alloying elements such as Cr, Al, Ni, etc. increases the surface hardness after the Tenifer ® treatment.

Wear resistance

By the degree of setting of the iron and alloying elements on the surface of the connection zone assumes non-metallic character. Characterized a matching non-metal / metal is produced at Gleitprozessen preventing welding and bonding, thereby increasing the wear resistance. A side effect is occurring in these pairings low coefficient of friction.

Stiffness

Due to the considerable increase in the surface hardness at the Tenifer treatment, a greater stiffness is achieved. This results in a higher level of security against bending or warping.

Corrosion resistance

Due to the nitrogen-rich bonding or diffusion zone of the material surface is given a certain protection against corrosive attacks. By a post-oxidation ( TUFFTRIDE Q method), it is possible to obtain an excellent corrosion resistance. Therefore, this method has been proven in the automotive industry. Tenifer QPQ ® -treated workpieces can a service life of 500 hours to reach ( for comparison: Chrome, 20 microns, about 80 hours, plated, 20 microns, about 100 hours) in the salt spray test.

Load-bearing capacity

Tenifer - layers have great strengths. Even after loading ( compression tests ) beyond the yield point ( elastic limit range / plastic range) out into the plastic range ( permanent deformation ) was to detect any damage to the surface; This requires a small change in shape.

Other properties

The sliding properties and wear resistance remain up to temperatures of 500 ° C and will shortly receive it too. Since the connection zone is a poorer conductor of heat than the base material, this does not heat as fast as without Teniferierung.

Swell

  • Röchling: Technical Bulletin, No. 10/April 1970 by Karl Sartorius and Karl Ibinger
  • Bargel / Schulze: Materials Science, VDI Verlag Dusseldorf, 1988
  • Publication Durferrit GmbH: http://www.durferrit.com/media/pdf/Tenifer_QPQ_deutsch.pdf
  • Change material properties
Tempering (metallurgy)
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