One of the key advantages of the Kolsterising® process is that it increases surface hardness significantly without introducing brittleness. Unlike traditional hardening processes, which can lead to the formation of brittle phases in the material, Kolsterising® diffuses carbon atoms into the surface layer of the metal without the formation of carbides. This results in a hard, wear-resistant surface while maintaining the ductility and toughness of the core material. As a result, the fasteners retain their overall strength and are less prone to cracking or failure under stress, even after the treatment.
Kolsterising® (-KOL/-N-KOL)
Kolsterising® is an industry-proven, thermo-chemical, low-temperature, diffusion-based, surface hardening technology used to enhance certain grades of stainless steel, cobalt, and nickel-based alloys. Kolsterising® is not a coating but a low-temperature surface carbon diffusion treatment that enhances the hardness of the base material. The process adds large concentrations of carbon atoms that form high compressive stresses on the surface. These stresses and the filling of the interstitial sites by the carbon atoms not only significantly improves the hardness of the material and maintains corrosion resistance, but also increases the surface resistance to wear and fatigue.
Kolsterising® is ideal for applications such as:
- Medical devices that require biocompatible materials
- Pharmaceuticals
- Fasteners
- Valve parts (balls, needles, seats, and housings)
- Food and beverage filling/dispensing machine pistons and seals
- Automotive components
- Marine parts
- Industrial fluid handling
- And so many more
Kolsterising® significantly reduces:
- Delamination
- Galling in stainless steel alloys
- Metal debris
Why choose Kolsterising®?
- Complex shapes can be effectively hardened by this process
- It offers consistent diffusion depth
- Improved abrasive wear
- Improved cavitation erosion resistance
- Increased fatigue strength
- Reduces galling
- Exceptional scratch resistance
- Does not affect the magnetic properties of the metal alloys
- Good dimensional stability
- The process does not change the part dimensions
Figure 1: Comparison of untreated and treated (Kolsterising®) stainless steel threads; Left: significant adhesive wear occurred after a torque of 54ft-lbs (73 Nm) was applied. Right: no galling, with 135ft-lbs (183 Nm) torque applied.
Figure 2: These plots compare the friction factors and measured loads using Hastelloy® C-276 fasteners in the untreated condition and those treated with Kolsterising®. It can be seen in the above charts that in the Kolsterised condition the friction factor remains constant and therefore the resulting load achieved is unaffected. Comparing this to the untreated fasteners, it can be seen that repeated loading causes the friction factor to increase and the resulting load to decrease indicating adhesive wear and galling of the thread has occurred.
Kolsterising® allows designers and engineers to use more common and inexpensive materials, while giving them the performance of more expensive alloys. The treatment can improve some austenitic and martensitic grades of metal, ferritic and duplex stainless steel, as well as certain cobalt-chromium and nickel-based alloys.
Kolsterising® FAQs
How does Kolsterising® change a fastener’s surface hardness?
Kolsterising® is a surface hardening process that combines increased durability while maintaining aesthetics. It is particularly beneficial for fasteners requiring reliability, longevity, high wear resistance, and dimensional stability in demanding environments.
Fasteners treated with the Kolsterising® process can achieve a surface hardness of up to 1,200 HV (Vickers Hardness). This significant increase in surface hardness is achieved without compromising the corrosion resistance of the underlying material. The exact hardness can vary depending on the specific material treated and the process parameters used. However, achieving around 1,000 to 1,200 HV is typical for austenitic stainless steels and similar alloys.
Does Kolsterising® affect the corrosion resistance of the treated fastener?
Kolsterising® often enhances the corrosion resistance of the treated fastener. The process involves diffusing carbon into the material’s surface without forming carbides, which allows the treated fastener to retain its original corrosion-resistant properties. Since Kolsterising® is particularly suited for stainless steels and other corrosion-resistant alloys, it preserves the material’s ability to resist corrosion.
The diffusion layer created by Kolsterising® is extremely hard and dense, which can act as an additional barrier against corrosive environments. Therefore, fasteners treated with Kolsterising® maintain their resistance to corrosion, making them ideal for use in harsh environments where both high wear resistance and corrosion resistance are critical.
How can fasteners from Pure Tech Components Ltd help you?
Pure Tech Components Ltd are the premier UK distributor for UC Components, Inc.
While the right coating or plating for your HV or UHV application is best defined by your process engineer, we are always here to assist you. Our supplier, UC Components, Inc. has been the world leader in high vacuum hardware since 1974.
UC Components, Inc.’s RediVac® fasteners, washers, nuts, and O-rings are designed for use in a wide range of high vacuum applications and other clean-critical environments. We offer a variety of specialized venting designs, numerous finishes, and complete Class 100/ISO Class 5 Cleanroom cleaning and packaging.