Gas carburizing

P/M steels can be heat treated in the same manner as cast or wrought steels. They may be austenitized, quenched, and tempered. Surface hardening includes pack or gas carburization or nitriding, ie, heating in a nitrogen-containing atmosphere. Because of the greater amount of exposed surface area in the form of porosity, a protective atmosphere is needed (see Metal surface treatments). 

If the gas has the correct composition, the carbon content at the surface increases to the saturation value, ie, the solubiUty limit of carbon in austenite (Fig. 2), which is a function of temperature. Continued addition of carbon to the surface increases the carbon content curve. The surface content is maintained at this saturation value (9) (Fig. 5). The gas carburizing process is controlled by three factors (/) the thermodynamics of the gas reactions which determine the equiUbrium carbon content at the surface (2) the kinetics of the chemical reactions which deposit the carbon and (J) the diffusion of carbon into the austenite. 

Carbon nitride, 27 214—215 conductivity of, 2 7 204-206 field emission properties of, 27 221 theoretical band structure calculations for, 27 203-204 Carbon nitride films, 2 7 205 Carbon nitride solids, 2 7 203 Carbonochloridic esters, 6 290 Carbon paper, 4 738-739 Carbon profile, in gas carburizing, 26 204 Carbon Raschig-ring tower packing, 22 745 Carbon reduction, of ferrovanadium, 25 518... 

Chemical textile finishing, 24 622 Chemical thermodynamics, of gas carburizing, 16 201-203 Chemical Transportation Emergency Center (CHEMTREC), 25 343 Chemical treatment of magnesium, 15 374 of spent nuclear fuel, 25 854 Chemical uses, for hydrogen peroxide,... 

Gas-based muds, 9 3 Gas bulk separation, 1 646-647 commercial processes, l 618t Gas burners, 7 455-460 Gas burner technology, 12 382-383 Gas carburizing... 

Case Hardening Replacing Salt Baths with Gas Carburizing and Nitrating, and with Applied Energy methods SR Kirk-Othmer 1981... 

Benz(crude) is obtd comly by fractnl distn of light oil, which in turn is formed as a by-product in the high temp destructuve distn of coal it is obtd from coke oven gas, carburated water gas, and by the cracking of gasoline under press and elevtd temp(Ref 7)... 

Committee on gas carburizing, A. S. M. Carburizing and carbonitriding, 1st Ed. (1977) Metals Park, Ohio, American Society for Metals... 

Parrish, G. and Harper, G. S. Production gas carburizing, 1st Ed. (1985) Oxford, Pergamon Reynoldson R. W, Advances in surface treatments using Fluidized beds. Surface and Coatings Technology., Vol. 71 2, pp. 102-107,1995. 

Heat-treatment Gas carburizing Furnace components 870-1090X Carburization... 

Gas carburizing Furnace brick anchors. 540-820 X Metal dusting... 

Carburization damage is mainly associated with high-temperature exposure to carbon dioxide, methane, and other hydrocarbons. Heat-treating equipment used for gas carburization (surface hardening) of steels is also vulnerable. An insidious aspect of carburization is its nonuniform nature. Just as for other forms of localized corrosion, it is extremely difficult to predict and model localized carburization damage. As a rule of thumb, carburization problems only occur at temperatures above 815°C, because of unfavorable kinetics at lower temperatures. Carburization is therefore not a common occurrence in most refining operations because of the relatively low tube temperatures of most refinery-fired heaters. 

A coating process, similar to gas carburizing and carbonitriding, whereby a reactant atmosphere gas is fed into a processing chamber where it decomposes at the surface of the work piece, hberating one material for either absorption by or accumulation on the work piece. A second material is liberated in gas form and is removed from the processing chamber, along with excess atmosphere gas. 

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