|
Definitions
Ferritic Nitrocarburing Definitions & Descriptions
-
Thermochemical diffusion process where nitrogen, carbon, and to a very
small degree, oxygen atoms diffuse into the surface of the ferrous substrate forming a compound layer and subsurface
diffusion layer. Objectively the diffusion is accomplished in a relatively short period of time and at subcritical temperatures. The resulting "white cast" or epsilon layer and subjacent diffusion
layer enhances the performance characteristics of the base metal material.
-
The primary objectives
- Improve wear properties
- Corrosion resistance
- Improve fatigue characteristics of the metal.
- Reduce soldering of die cast dies and associated components.
-
Nitrocarburizing requires a source of carbon, and nitrogen
-
Simple nitriding can be done in a gas, liquid salt, or plasma (electrically
charged ions) environment.
Fluidized Bed Nitrocarburizing
-
Less controllable Advantages over Gas and Salt methods
-
Reduced Cycle Times
-
Faster Recovery
-
Rapid changes of atmosphere compositions
-
Disadvantage - media contamination of water lines and orifices
Historical Prominent Developers
Salt Bath Nitrocarburizing
-
About 50 years ago commercial methods of ferritic nitrocarburizing in molten salts came into existence on a commercial basis. The first process in France was called "Sulfiniz" and used cyanide and cyanates salts plus a small amount of sulfur bearing compounds.
-
In 1959 a modified version patent from Germany was filed for an aeration oxygen source which was called "Tufftride".
-
The 1970's EPA regs impacted the cyanide based materials and new salt compositions were developed that eliminated this deadly, caustic, and
carcinogenic material. The new non-cyanide salt is called Melonite along with a French process called "Sur-sulf". These two salt bath processes are still being used commercially today.
Gas
-
Originally patented in 1961 by Joseph Lucas Industries Ltd.
-
Gaseous type (in 1965 B. Presnosil published results of study of this method of nitriding.)
-
During the following quarter of a century a number of gaseous nitrocarburizing processes were developed of which some were patented. Some of these include, Triniding (ammonia and exothermic gas. This was succeeded by Nitemper, Lindure, and two stage process called Deganit out of Germany.
Click on the underlined names for descriptions of various nitrocarburizing methods..
|
