Nitrocarburizing
Nitrocarburizing treatment in a nitrogen-based atmosphere is substantial and comparable with that produced by conventional 60h gas nitriding of same material. In view of the fact that the effective case depth of the nitrocarburized component is approximately 50% of that of a nitrided component , the wear performance can only be attribute to the properties of the compound layer.
The fatigue resistance obtained by 3 h nitrocarburazing is within specification for the automotive crankshaft.
The adoption of a short-cycle nitrocarburizing treatment in this instance would yield a saving in heat treatment costs of some 85%
In addition it has been shown that the nitrocarburized surface facilitates the use of a cheaper bearing than that required for more friable surface of the nitrided component.
(Practical nitriding and ferritic nitrocarburizing ; David Pye , pg : 229 , First Edition)
Carbon Restoraiton
To increase the carbon content of molten cast iron or steel by adding carbonaceous matierial ,high carbon pig ireon , or a high –carbon alloy .
To carburize a metal part to return surface carbon lost in processing ; also known as recarburize.
(ASM materials engineering dictionary; Joseph R. Davis; 362 ;2006)
Hardenability
Hardenability is the ability of the Fe-C alloy to be hardened by forming martensite . Hardenability is not “hardness” . It is a qulitatice measure of the rate at which hardness decreases with distance form the surface because of decreased martensite content .High hardenability means the ability of the alloy to porduce a high martensite content throughout the volume of specimen.
The hardenability of a steel is broadly defined as the property which determines the depth adn distribution of hardness induced by quenching . Hardenability is a characteristic determined by the following factors.
Chemical composition
Austenite grain size
Structure of alloy before quenching
The hardenability is the depth and evenness of hardness of a steel upon quenching form austenitc.
(A Textbook of Engineering Materials and Metallurgy ; A.Alavdeen, N. Venkateshwaran ; pg: 232 , 2006 )
Cryogenic Treatment
In early 1990s method were developed to reduce temperatures even further to -300 F* making it possible to improve the properties even more ; this process is called Cryogenic Treatment , In Cryogenic treating , parts are chilled to approcimately.( -300F* -185*) Benefits form cold treatment range form anhancing transformation from austenite to martensite , to improving the stress relive of casting and machined parts . In each case , even greater benefits are realized as a result of cryogenic treatment.
Heat treating geves steel its hardness , thoughness , wear resistance , and ductility . Heat treating is really a misnomer , it really should be called cold treating.
(Exploring advanced manufacturing Technologies ; Stephen F. Krar, Arthur Gill , pg 11-1-2 ; 2003)
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