Salt bath nitriding
Salt bath nitriding is a physicochemical process in which a diffusion zone is created on the finished workpiece following heat treatment.
To do this, the components arepreheated uniformly to approximately350 °Candthen immersed in anitriding bath heated to 580 °Cwitha controlled cyanide-cyanate content. The immersion in the molten salt bath lasts anywhere from a few minutes to a few hours, depending on the steel composition and shape.
Once the specified treatment time has elapsed, the workpieces are quenched in quenched in water, oil, or a polymer. In addition to the incorporation of nitrogen, carbon always diffuses into the component surface during salt-bath nitriding. This is a key reason for the positive, specific surface properties of salt-bath-treated components.
To do this, the workpiece is immersed in an oxidizing bath at approximately 380 °C immediately after the nitriding bath and held there for 10–15 minutes. The oxidation process neutralizes any adhering cyanide and converts it into non-toxic sodium carbonate.
Corrosion resistance can be improved through a post-treatment in an oxidizing bath, known as the AB1 bath.
The new surface, whose corrosion resistance is superior to that of galvanic coatings in many cases, takes on an attractive black color.
This is followed by quenching in water, followed by drying and polishing. Tenifern is suitable for a wide variety of materials, such as stainless, unalloyed, low-alloy, or high-alloy steels, cast iron, ductile iron, or sintered metals.
KEY FIGURES FOR SALZBADNITRIEREN
Temperature:
up to 580°C
System size:
500 x 500 x 500 mm
Processing time:
Starting at 1 week
Nitriding hardening depth:
up to 0.5 mm
Advantages of Salt Bath Nitriding
No delay
Nitriding is the only hardening process that does not cause any process-related distortion of the component.
Hardening of specific areas
Specific areas of the component can be hardened by covering the other surfaces with a protective paste.
Outstanding component properties
Nitriding produces components with improved corrosion resistance and high wear and fatigue strength, capable of withstanding the most severe loads.
No post-processing
Since no distortion occurs during the hardening process, components can generally be nitrided after they have been manufactured.
Wear resistance, fatigue resistance, and corrosion resistance
Salt bath nitriding is widely used, not least because of its outstanding corrosion resistance and attractive appearance. The process is characterized by a short treatment time and reproducible quality standards.
It is frequently used, particularly for automotive components and mechanical engineering tools.
Since no microstructural transformation occurs during salt-bath nitriding and the thermal stresses are very low, no significant dimensional changes are to be expected. Wear resistance, fatigue resistance, and corrosion resistance increase significantly after salt-bath nitriding. These nitrided layers are heat-resistant up to 500 °C and also exhibit high toughness —even after being subjected to loads exceeding the yield strength, no surface damage is visible.
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Silvio Stranek
Sales, Technical Consulting / Quotes (Upper Austria, Tyrol, Salzburg, Vorarlberg, Bavaria, South Tyrol)
Email. s.stranek@htr.at
Phone: +43 (0) 664 / 88 92 78 10
Thomas Stadlober
Sales, Technical Consulting / Quotes (Styria, Vienna, Lower Austria, Carinthia, Slovenia)
Email. t.stadlober@htr.at
Phone: +43 (0) 664 / 88 64 15 06
OTHER NITRIDING PROCESSES
gas nitriding
In gas nitriding, nitrogen is released from ammonia; at temperatures between 500°C and 600°C, this nitrogen penetrates the surface of the component, where it forms a wear-resistant nitride layer.
Plasma nitriding
In plasma nitriding, the surface layer of a workpiece is enriched with nitrogen in an ionized gas atmosphere. This results in clean component surfaces with significantly improved resistance to abrasion and wear.
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OUR INDUSTRIES
Automotive industry
Aerospace
Medical technology
Tool and Machine Manufacturing
Your Questions, Answered
We have compiled a list of frequently asked questions to help you better understand our services.
What is salt bath nitriding?
Salt bath nitriding is a chemical-physical hardening process in which components are immersed in a hot nitriding salt bath. This creates a wear-resistant, corrosion-resistant surface layer. The surface is then further refined through oxidation in what is known as an AB1 bath, giving it an attractive black color.
How does the process work?
The process consists of several precisely controlled steps:
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Preheattheworkpieces to approximately 350°C.
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Nitridingina salt bath heated to approximately 580°C with a specified cyanide-cyanate content.
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Quenchinwater, oil, or polymer.
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Oxidizeinan AB1 bath heated to approximately 380°C (10–15 minutes).
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Final drying and polishing.
During this process, nitrogen and carbon diffuse into the surface layer, resulting in excellent material properties.
What are the advantages of salt bath nitriding?
Salt-bath nitriding offers a wide range of outstanding advantages. A key benefit is the absence of warpage: There is no process-induced dimensional change, so the components retain their original geometry. The surface properties are also impressive. The process ensures high wear resistance, improves fatigue resistance, and provides excellent corrosion protection. The subsequent oxidation step also produces a uniform, aesthetically pleasing black surface. Another advantage is the high reproducibility of the process: The short treatment times result in consistently high quality. The nitriding layers are heat-resistant up to 500°C heat-resistant and are characterized by high toughness —even when subjected to excessive stress beyond the yield strength, the surfaces remain intact.
Which materials are suitable?
Salt bath nitriding (e.g., the Tenifer process) is suitable for a wide range of materials:
– Stainless steels
– Unalloyed, low-alloy, and high-alloy steels
– Cast iron and ductile iron
– Sintered metals
Suitability depends, in detail, on the composition and surface of the components.
Where is salt bath nitriding used?
Due to its reliability and consistent results, this method is particularly well-suited for:
– Automotive industry(e.g., powertrain components, piston pins)
– Mechanical Engineering(Tools, High-Stress Components)
– Components with high requirements for dimensional accuracy and corrosion resistance
What are the technical requirements?
– Process temperature:up to580 °C
– System dimensions: 500 × 500 × 500mm
– Turnaround time: 1 weekor more
– Nitriding hardening depth:up to0.5 mm