Vacuum Chromizing Technology

Vacuum chromizing, which involves treating steel in chromium vapour under low pressure conditions, is used for improving properties of steel surface such as hardness, wear, corrosion resistance and thermal oxidation. The chromizing processes is carried out in a cold-wall vacuum oven at the temperature range 1050÷1200°C, for various times. The pressure range of these processes was extended from 10 Pa down to10^-2 Pa.

The vacuum chromizing technology is environmental safe (no waste). In contrast to other chromizing methods (powder, gas, etc.), neither toxic reagents i.e. chlorides nor a hydrogen containing atmosphere have been used.

 

Carbon content plays an important role in the diffusion chromizing of steels, since its diffusion to the surface during the process leads to its combination with chromium to form carbides. At high carbon content in steels, the obtained diffusion layers are composed of chromium carbides. Such layers are hard and wear/erosion/abrasion resistant (hard chromizing). Corrosion resistance is characteristic of layers (of chromium in iron solid solution structure) obtained on the surface of pure iron, low carbon steels or all ferrous metals with < 0.1% C (soft chromizing). Chromizing offers both performance and economic advantages for wide range of applications. The technology make it possible to design the surface of inexpensive carbon steel, cast iron or low alloy steel for specific environments and conditions.

 

Hard chromizing

• Chromium carbide layer thickness 5 - 30 microns
• Hardness approx. 2000 Vickers
• Very low coefficient of friction
• Prevents cold shot
• Corrosion resistance and very high oxidation resistance
• Suitable for all ferrous metals
• Hardening after hard chromizing is possible

Application: tools for hot-working, tools for cold-working, components for textile machine, component parts for use in food processing industry, component parts for the chemical industry, stamping and drawing tools and dies, pistons, dies for glass forming.

 

Soft chromizing

• Layer thickness 30 - 500 microns
• Highly elastic, therefore deformable
• Heat resistance up to 850°C
• Corrosion and erosion resistant
• Suitable for all ferrous metals with < 0.1% C

Application: apparatus of water supply system, bolts, water pump elements, pipe bends, component parts for the chemical industry, gas turbine blades, furnace components, incandescent elements, furnace components and gas burners.
The invention "Vacuum chromizing technology" was awarded with GOLD MEDAL on 6th International Exhibition of Inventions, INNOVATION 2005, Gdansk, PL, 19-21 October 2005.

Patents:

• Kasprzycka E., Tacikowski J., Zyśk J., Jarzyński J.: Vacuum chromizing method of steel, Patent RP nr 159 324, Warszawa 1993
• Ewa Kasprzycka, Aleksander Nakonieczny, Tomasz Babul, Bogdan Bogdański: Patent notification EP-1989 z dnia 29.03.2005 pt. Vacuum chromizing method of products from iron alloys, IMP Warszawa 2005
• Ewa Kasprzycka, Aleksander Nakonieczny, Andrzej Przywóski: Patent notification EP-1992 z dnia 06.04.2005 pt.: Method of corrosion resistance improvement of diffusion chromized layers, IMP Warszawa 2005