Abstract: A method for the heat treatment of cadmium mercury telluride homogeneous single crystals is disclosed wherein the crystals are heated and maintained at a temperature in the range of from about 300 K to below the solidus temperature of the composition treated in the presence of mercury, the vapor pressure of mercury being less than the saturation vapor pressure of mercury.

Abstract: A method and device for control of the carbon level of a gas mixture reacting in a heat treatment furnace, which gas mixture arises by means of the introduction of a fuel containing hydrocarbon into the furnace chamber, the reaction products of which are not in a state of water-gas equilibrium and not in a state of methane gas equilibrium and which gas mixture has an excess of methane. The controlled condition is determined by a first measurement device from the portion of the gas component CO which is present in the furnace chamber as a first measured value, and by a second measurement device from the electrical voltage of an oxygen-ion-conducting solid body electrolyte as a second measured value and by a third measurement device from the furnace chamber temperature as the third measured value. A regulating member is controlled as a result to automatically change the quantity flow of the supply to the furnace chamber until correspondence of the measured carbon level with its desired value exists.

Abstract: A method of hardening steel so that it may have a surface layer with sufficient hardness to permit fabrication into machinery parts with a minimum of strain developed therein. The method comprises heating steel at a temperature in a range not lower than 100.degree. C. below its A.sub.1 transformation point (about 630.degree. C.) and not higher than 50.degree. C. thereabove (about 780.degree. C.) in an atmosphere consisting solely of ammonia gas, or composed of ammonia gas and at least one of organic liquids, petroleum gases, endothermic gases and neutral gases, while ammonia gas is being supplied continuously at a lower flow rate, or at a higher flow rate followed by a diffusion treatment to austenitize a surface layer of the steel by penetration of nitrogen thereinto, and quenching the steel to transform the austenitized surface layer into a martensite layer.

Abstract: Oxygen sensor comprising solid oxygen-ion-conducting electrolyte with a platinum group metal film electrode contacts and monitors nonoxidizing or reducing gas atmosphere in a metal heat treatment (gas carburizing) furnace after a getter of the same platinum group metal as in the film electrode removes platinum group metal contaminants from such atmosphere before it contacts the electrode. Getter is held in a thin-walled, multi-passaged honeycomb body.

Abstract: A process for suppressing electromigration in conducting lines formed on integrated circuit structures includes the steps of forming the conducting lines on the integrated circuit structure and heat treating the lines to cause the average grain size in the lines to become larger than the width of the conducting lines.

Abstract: This invention relates to a method of heat treating articles which utilizes a fluidized bed comprising a container containing a mass of refractory particles and having a porous base, a layer of such particles adjacent to the porous base being formed of heavier particles than the remainder of said refractory particles. According to the invention, a non-stoichiometric fluidizing and treatment medium is supplied to the underside of the porous base and flows therethrough into the mass of refractory particles at such a velocity as to leave the heavier particles unfluidized while fluidizing the remainder of the particles. A gaseous medium is also introduced into the container at a position above and spaced from the porous base to together with the non-stoichiometric fluidizing and treatment medium, a combustible mixture which is ignited to heat the mass of refractory particles to a temperature at which the non-stoichiometric fluidizing and treatment medium will carry out the desired heat treatment.

Abstract: Material surfaces are provided which maintain their characteristic properties over long periods and which resist degradation by the environment in which they are utilized. The surfaces are formed by exposing a surface of atomically clean material to a gas or liquid which interacts with the clean surface to form a composition having the properties desired and which is stable against degradation in the environment of use. The process is useful, for example, to render metals or metal alloys, such as iron or iron alloys, stable against oxidation by air by exposing the atomically clean surface to an ultrapure nitrogen environment, prior to exposure to a degrading environment, such as air. A new oxidation-resistant iron surface composition also is provided which comprises body-centered iron structures including nitrogen atoms interstitially.

Abstract: An apparatus and method is provided for heat treating a tubular type heat exchanger. A heat fluid is passed through the tube bundle in order to heat the exchanger from within.

Abstract: On degrease annealing of thin strip and foil made of aluminum and aluminum alloys in an annealing furnace ozone is introduced into the furnace atmosphere.As a result of this the annealing time can be shortened or the annealing temperature lowered. Likewise the tendency for the foil to stick together when in coiled form is markedly reduced.

Abstract: A process for carburizing ferrous metal articles in a furnace under an atmosphere derived from an input of nitrogen and ethanol injected into the furnace during the entire cycle. Carburization is controlled in a first embodiment by the control of ethanol and nitrogen mixture and water vapor content of the mixture as well as total flow through the furnace and in a second embodiment by controlling the nitrogen-ethanol mixture to which is added water and an enriching or carburizing agent.

Abstract: Disclosed is an improved ion-nitriding process comprising ion-nitriding a workpiece at a high voltage level of glow discharge in a gas atmosphere resulting from the introduction of a gas mixture containing a specific amount of ammonia into a nitriding reactor, and then, further ion-nitriding the same workpiece at a lower voltage level of glow discharge in a gas atmosphere resulting from the introduction of a gas mixture not containing ammonia into the reactor.

Abstract: In a process for carburizing steel parts, wherein it is desired to shut down the carburizing process for a predetermined period of time without removing the parts,the improvement comprising the following steps:(a) introducing parts, which would not achieve 100 percent carburization prior to the shut down of the carburizing process, into the furnace;(b) determining the temperature (Tc,s) for each temperature zone at about which the parts introduced in step (a) are to be maintained in step (c) ##EQU1## wherein: ##EQU2## (c) maintaining the parts in the carburizing atmosphere at the temperature determined in step (b) for that temperature zone;(d) reducing the amount of the hydrocarbon component of the atmosphere;(e) gradually lowering the temperature from the level of step (c) to a predetermined level, less than about 1400.degree. F.;(f) during step (e), but before the temperature reaches about 1400.degree. F.

Abstract: A process for carburizing steel in a furnace under an atmosphere derived from the decomposition of an oxygenated hydrocarbon containing up to three carbon atoms, no more than one carbon to carbon bond, and a carbon to oxygen ratio of from 1 to 2 such as alcohols, aldehydes, ethers, esters and mixtures thereof. The oxygenated hydrocarbon injected into the furnace produces an atmosphere under which an initial rapid stage of carburization takes place. After the initial rapid stage of carburization gaseous nitrogen is blended into the oxygenated hydrocarbon atmosphere throughout the remainder of the process with a concurrent reduction in the rate of injection of oxygenated hydrocarbon while maintaining volumetric flow through the furnace during the entire carburizing cycle. During the entire carburizing cycle, the carbon potential of the furnace atmosphere can be controlled by addition of a hydrocarbon gas enriching or carburizing agent.

Abstract: An improved columnar grained, polycrystalline, anisotropic article is provided of a Ni-base, carbide fiber reinforced eutectic alloy by a method of providing a unidirectionally solidified cast body which includes such fibers aligned and embedded in a gamma-gamma prime structure. Such body is heated at a first temperature to fully solution the gamma-gamma prime without melting the carbide fibers; exposed to a second, lower, temperature to precipitate fine gamma prime in substantially cuboidal shape within the size range of 1-4 microns; and exposed to a third, still lower, temperature to perfect such cuboidal structure without refinement or coarsening. The resultant article is characterized by improved longitudinal stress rupture life.

Abstract: An iron powder developing carrier for developing an electrostatic latent image, a manufacturing method thereof, a developer containing said developing carrier and a method of forming a visible image by using said developer.Said iron powder developing carrier has the apparent density from 1.5 to 2.5. Said manufacturing method comprises the steps of sintering a raw iron powder having been ground to particles of not larger than 50 microns in diameter without using any binder agent at the temperature from 900.degree. to 1200.degree. C. to form an sintered body, grinding and classifying said sintered body into an intermediate iron powder having the particle diameter from 50 to 200 microns, then treating said intermediate iron powder to oxidize at the temperature from 280.degree. to 390.degree. C., and adjusting the resultant iron powder so as to have the apparent density from 1.5 to 2.5.

Abstract: In order to decarburize ferrous metal without recourse to an exothermic generator, an inert gas (typically nitrogen), water and a liquid or vaporous compound of carbon, hydrogen and oxygen (typically methanol) are admitted to a working chamber of the heat treatment furnace in which the metal is situated. The decarburization is preferably performed at 700.degree. to 800.degree. C. The methanol and water react to form a non-oxidizing, decarburizing atmosphere at the decarburizing temperature. The metal may be oxidized at a temperature below 600.degree. C. in another chamber of the furnace, the atmosphere from the decarburizing chamber being passed into the oxidizing chamber.

Abstract: PCT No. PCT/US79/00792 Sec. 371 Date Sept. 27, 1979 Sec. 102(e) Date Sept. 27, 1979 PCT Filed Sept. 27, 1979Parts (12) to be treated are placed in grid bottomed tubs (14a,14b,14c) and the tubs (14a,14b,14c) are stacked one upon the other. A flow of treating gas is directed exteriorly about and internally through the tubs (14a,14b,14c) from an entrance end (26) to an exit end (28). If the parts (12) in the entrance tub or tubs (14a,14b) are sufficiently but not overly treated, it has been found that the parts (12) near the exit end (28) of tub or tubs (14b,14c) are not sufficiently treated. If the parts (12) near the exit end (28) tub or tubs (14b,14c) are sufficiently treated, then the parts (12) in the entrance end (26) of tub or tubs (14a,14b) are over treated.

Abstract: During the process of movement of an aluminum strip in a floating mode, the strip is first heated and then cooled for the annealing. In cooling the aluminum strip, the aluminum strip is first cooled to a predetermined temperature at an easy cooling temperature gradient, and subsequently cooled to a room temperature at a sharper cooling temperature gradient than the former. During the process of the cooling, a significant thermal stress is not produced in the aluminum strip, and the aluminum strip is cooled without being wrinkled.

Abstract: A vibrating member made of a thin metal plate and adapted to be used in an acoustic transducer such as a loudspeaker or microphone is diffused at least partially with an inorganic substance to improve the acoustic characteristics thereof, particularly the high frequency range.

Abstract: A property, such as ductility, mechanical strength and increased remelt temperature, of an alloy, for example one which includes an element such as Si or B, or both, is improved by depletion of such an element through the alloy surface. This is accomplished by exposing the alloy surface, one common form of which is a brazing alloy, to gaseous ions such as fluoride ions, while heating the alloy at a temperature which is not detrimental to the alloy or members associated with the alloy. Heating is conducted for a time sufficient for such elements, for example those selected from Si and B, included as a melting point depressant, to diffuse to the surface of the alloy and to react with the gaseous ions to form a gaseous compound of the element. Such gaseous compound then separates from the surface, thereby depleting the alloy of the element and improving at least one property.

Abstract: Aluminum or its alloy is subjected to surface treatment wherein the surface is heated and melted by the heat of an electric arc in an atmosphere of a mixture of inert gas and nitrogen gas. By this treatment, a dense layer of aluminum nitride is formed on the surface of aluminum or its alloy so that material of increased wear resistance is obtained.

Abstract: Method of nitriding steel surfaces by circulating thereover a ternary mixture of ammonia, hydrogen and water at an elevated temperature and atmospheric pressure. Most of the harmful effects of HCN formation are avoided by utilizing a furnace lining consisting of a coated nickel base alloy, and by adding from 1 to 3% water to the nitriding gas and flowing the nitriding gas at a rate as low as 5 to 20 cu. ft. per hour per 100 sq. ft. of steel surface area.

Abstract: This invention relates to a process for the production of a solid solution of compounds consisting of, in combination, at least 10 mol %, based on all metallic components, of molybdenum, at least one metallic element selected from the Group IVa, Va and VIa elements of the Periodic Table and at least one of non-metallic elements, which comprises mixing the metallic elements in the form of compounds or solutions thereof, adding carbon, optionally with at least one of non-metallic elements to the mixture, subjecting the resulting mixture to a reducing reaction with carbon and then subjecting to a solid solution-forming treatment in a reducing, carburizing or nitriding atmosphere.

Abstract: A process of annealing for preventing temper colors on a steel sheet in a box annealing furnace, which comprises placing an oxidizable iron-base material at a position of low temperature in a circulating path of a furnace gas.

Abstract: In a process for carburizing ferrous parts, nitrogen gas is supplied to the vestibule of an integral quench furnace while a gaseous carbon source is supplied without a carrier gas to the furnace hot zone. H.sub.2 O is introduced into the hot zone at the rate of 0.1-15 ml/min such that upon vaporization thereof a furnace hot zone atmosphere is formed which includes up to about 40% nitrogen, at least 14% CO and 40% H.sub.2. Subsequent to carburizing, parts may be annealed or bright hardened in the same furnace by increasing the H.sub.2 O flow rate to the hot zone to establish an atmosphere comprised of at least 60% H.sub.2.

Abstract: Method and apparatus defining a combustion and fluidized heating system for the heating of ladles of the type commonly used in the foundry and steel industry is described whereby fluidized-bed technology is employed to achieve greatly improved fuel efficiency. In the method, the particles forming the substance of the bed are placed directly into the ladle. The same may be drawn from a prior heated ladle. In practice, the initial heating medium be it gas or liquid or solid or electric may be replaced in final heating by the direct introduction into the bed of solid or fluid fuel to achieve combustion within the bed itself. Alternatively the bed may be heated electrically as by immersion of an electric resistance heater in the bed. Control of the combustion and the fluidizing medium is inherent in operative characteristics of the invention.

Abstract: In a continuous annealing process, the annealing furnace is comprised of two adjacent chambers, one for heating and the other for cooling with a door therebetween. The strip coil to be annealed is brought into the heating chamber, such as by a vehicle on a rail, the heating chamber closed, and the coil heated. After heating, the interconnecting door is opened and the heat coil is moved into the cooling chamber by the vehicle, the cooling chamber is closed and the coil is cooled. Concurrently, the next charge of coil is moved into the heating chamber and heated. Since heat from the previous cycle is still in the heating chamber, the amount of heat required for the next cycle is less and heating efficiency is substantially increased. Also, no movement of other equipment is necessary since only a horizontally movable vehicle is necessary to move the coil from one chamber to the next.

Abstract: A super conductor is made by first shaping a copper strip carrying a niobium layer into a corrugated tube; thereafter tin is deposited on the tube which is coiled, hung from a ceramic rod and placed into an annealing furnace being evacuated thereafter, the interior of the tube is sealed off from the interior of the furnace. After, e.g. two hours of heating for causing the tin to diffuse into the niobium, a sufficiently thick layer of Nb.sub.3 Sn has developed and a cold inert gas is flushed through the tube to rapidly cool the tube while retaining it in the evacuated but no longer heated furnace.

Abstract: Aluminium or silicon is diffused into iron (including silicon-iron) by applying to the iron an aqueous paste containing powdered aluminium/silicon, sodium silicate, and optionally magnesium oxide and colloidal silica, and firing it.

Abstract: A method is disclosed for capless annealing compound semiconductors such as ion-implanted GaAs semiconductors. The surface of the semiconductor to be protected during annealing is placed in loose physical contact with an inert material such as powdered graphite. The assembly is placed in a controlled atmosphere and heated to the annealing temperature where it is maintained until annealed. The semiconductor is cooled and then removed from the controlled atmosphere and inert material. In one embodiment, a volatile one of the elements in the compound is introduced into the inert material.

Abstract: A method and apparatus for the control of the carburizing of parts under vacuum in a vacuum furnace, with which as a carbon carrier a hydrocarbon gas is introduced controlled in the furance. As the control quantity a soot mist formation is used in such a manner that the occurrence of the soot mist is determined, that upon the occurrence of the soot mist the hydrocarbon addition is completely or partially interrupted, and that the hydrocarbon addition is again received if the soot mist formation has dampened out.

Abstract: A method of improving the mechanical properties of a .gamma./.gamma.'-.alpha. eutectic nickel-base superalloy body containing a .gamma.-phase, a .gamma.'-phase, and an aligned molybdenum fiber .alpha.-phase which comprises the steps (a) heating the body to a temperature at which at least a portion of the .gamma.'-phase will transform to a .gamma.-phase, (b) maintaining the heated body at said temperature to allow transformation of at least a portion of said .gamma.'-phase to a .gamma.-phase, and (c) cooling the transformed body to a temperature at which at least a portion of the .gamma.-phase precipitates as a modified .gamma.'-phase.

Abstract: A process is provided for heating steel powder compacts in a controlled atmosphere consisting of a primary gas containing at least 80% by volume of an inert gas, and a secondary gas comprising 0.1 to 5% by volume, based on the volume of said primary gas, of a paraffinic hydrocarbon. The process makes it possible to reduce the residual oxygen concentration in the steel powder compacts, while maintaining accurate control of the carbon content.

Abstract: In a process for carburizing steel in a furnace, using a defined carburizing atmosphere and regulating in defined manner the hydrocarbon component according to the amount of carbon dioxide present; maintaining a high flow rate when the passage through which the steel passes is open and a low flow rate when it is closed; and closing all other passages through which gas can pass.

Abstract: The present invention relates a method of making a hydrogen storage alloy comprising the steps of: preparing an alloy having, as main elements, 37 to 42 atomic percent of titanium and 58 to 63 atomic percent of manganese, which alloy is produced directly in an argon arc furnace or an induction furnace; heating the prepared alloy in an electric furnace at a high temperature below the melting temperature of the alloy under vacuum or an inert atmosphere; and cooling the heated alloy down to room temperature. The method of the present invention allows the alloy to have a homogeneous single phase, thereby providing an alloy with excellent hydrogen storage characteristics.

Abstract: In a process for sintering powder metal parts comprising:(a) passing the parts through a furnace adapted therefor from its upstream end to its downstream end, said furnace having two successive zones, an upstream zone, which is maintained at a temperature in the range of about 800.degree. F to about 2200.degree. F and a cooling zone, said furnace further having an atmosphere therein comprising carbon monoxide, hydrogen, carbon dioxide, water and nitrogen distributed throughout the zones;(b) permitting the parts to reside in the upstream zone for a sufficient length of time to cause sintering; and(c) removing the sintered parts from the furnace, the improvement comprising: introducing a mixture consisting essentiallyOf methanol and nitrogen into the upstream zone at a point where a temperature of at least about 1500.degree.

Abstract: A casting alloy consisting essentially of 20 to 40% chromium, 2 to 12% molybdenum, up to 2% silicon, up to 5% manganese, up to 1% carbon, 0.1 to 1% nitrogen, and the remainder cobalt and the usual impurities inherent to the manufacturing process. The alloy is subjected to a heat treatment to homogenize the lattice of the alloy, and thereafter the alloy is rapidly quenched in order to prevent reformation of deposits in the lattice.

Abstract: A method of improving certain characteristics of cadmium mercury telluride single crystal material by heat treating the single crystal material in the presence of both tellurium and mercury.

Abstract: A bearing part comprises an age hardened cobalt alloy having a bearing surface exposed to bearing friction provided with a boride covering layer. The bearing part is manufactured by forming a ductile age hardening alloy of cobalt and ageing it by heat treatment and meanwhile depositing a layer of boride onto the bearing portion of the alloy at a temperature of from between 550.degree. to 900.degree. C by diffusion from a vapor phase or a solid phase.

Abstract: The invention relates to a method of and an installation for the heat treatment of steels, such as heating before hardening, annealing, and carburization, which heat treatment is carried out in a furnace in the presence of a protection or carbon-enrichment atmosphere which flows continuously through the furnace, the atmosphere being obtained by the mixture, before its introduction into the furnace, of a carrier gas including nitrogen and possibly hydrogen, and an active gas constituted by a hydrocarbon, the mixture containing at least 0.2% by volume of hydrocarbon.The active gas may be constituted by ethylene, ethane or acetylene and the treatment is carried out at a temperature between 850.degree. and 1050.degree. C.The installation includes a device for analyzing the atmosphere at the furnace outlet, this analyzer actuating a regulating valve for the inlet flow of active gas through a servo-mechanism, in dependence on the proportion of carbon in the treated steel.

Abstract: Method and apparatus for heating ladles of the type commonly used in the foundry and steel industry is described whereby fluidized bed technology is employed to achieve greatly improved fuel efficiency. In the method, the particles forming the substance of the bed are drawn directly into the ladle from a mother fluidized bed unit wherein a flow balancing is effected to establish a relatively steady state, simultaneously as the flow to various ladles under treatment may be changed. The invention is particularly adapted to the use of coal as a fuel.

Abstract: An ionization detector, such as an electron capture detector for use in pesticide residue analysis, utilizes a scandium tritide beta particle source. The scandium tritide forms a surface portion of a metallic foil. If the foil initially exhibits an unacceptably high tritium emanation rate at desired high operating temperatures, e.g., at temperatures above 250.degree. C, the foil can be treated so as to exhibit an acceptable tritium emanation rate at such temperatures. The treatment comprises heating the foil at a predetermined treatment temperature, e.g., at a selected temperature in the 300.degree. to 400.degree. C range, until the tritium emanation rate for the foil at the selected treatment temperature reaches a value which correlates with an acceptable tritium emanation rate for the foil at a particular desired operating temperature.

Abstract: The heat treatment of a continuous band or sheet of metal as the same travels through a plurality of stages in a protective atmosphere, between conveying rollers, by applying direct-current electricity to the rollers for inclusion of the travelling sheet in the circuit therebetween. The charged rollers in the initial stage are spaced more widely from one another than those in the later stage, to compensate for the lower resistivity of the metal in the former, so that the Joule effect of I.sup.2 R factor in the stages are substantially equalized. The protective atmosphere of oxidizing, reducing or inert gases which encompasses the sheet, is confined in chambers of galvanized iron sheeting and the like, the walls of which are in close proximity to the travelling sheet, so that lesser amounts of reacting gases are necessary.

Abstract: A niobium containing alloy amterial is initially annealed in a hydrogen atmosphere at a temperature approximating 700.degree. C. The alloy material is then immersed in an aqueous solution of approximately between 1.0%-20.0% by weight of sodium hydroxide being maintained at a temperature of at least 70.degree. C. Immersion of the alloy material in the aqueous solution removes niobium oxide which is formed in the surface portion of the alloy material during the annealing step. After removal of the alloy material from the aqueous solution, the alloy material is plated on its surface with an electric contact material.

Abstract: A corrosion-resistant spinneret, suitable for spinning filaments of poly(p-phenylene terephthalamide) from a viscous solution of the polymer in 98-100 percent sulfuric acid, is prepared from a plate of tantalum alloy or stainless steel which is clad on one face with a layer of pure tantalum. A spinneret blank is formed, counterbores are drilled through the plate and partially into the tantalum layer, the blank is annealed, spinneret capillaries are formed from the counterbores through the tantalum layer to the exit face of the spinneret, the face is polished to remove protrusions, and the face is hardened by heat-treatment in nitrogen. Uniform capillaries having a diameter of about 0.002 inch (0.05 mm) and a length greater than about 0.005 inch (0.13 mm) can be formed in spinnerets without breaking tools used in their production.

Abstract: A low-carbon ferrochrome alloy containing a decreased amount of nitrogen can be made by this method. This method is conducted in a hydrogen stream and does not necessitate use of vacuum technique. A product of high purity can be obtained relatively simply and economically.

Abstract: The present invention relates to a method of carburizing and carbonitriding steel parts in the work chamber of a vestibule furnace with a substantially reduced consumption of carbon sources by exposing such parts to a gaseous carbon source such as natural gas while supplying an inert gas to the vestibule at a sufficient rate to control the entry of atmospheric decarburizing agents into the work chamber and to maintain the oxygen content in the vestibule at safe levels, below a minimum level required for supporting combustion or for allowing local puffs and explosions. The vestibule furnace may be of the batch or continuous type. In addition, the carbon potential of the atmosphere within the work chamber of the furnace is preferably continuously sensed and in response to such sensed carbon potential, the flow of natural gas to the work chamber is controlled so as to maintain the carbon potential at a predetermined value.

Abstract: A method of internally nitriding and thereby strengthening cobalt-base superalloys having at least 33% cobalt, up to 0.15% carbon, no more than 25% nickel and from 1 to 3% of nitride forming elements from the group consisting of titanium, vanadium, niobium, tantalum and zirconium. The method comprises the steps of: heating the cobalt-base alloy at a temperature of from 1600.degree. to 2500.degree. F in a nitrogen-bearing atmosphere substantially free of moisture and oxygen, and diffusing nitrogen from said atmosphere into and throughout said alloy for a period of time sufficient to form nitrides having an interparticle spacing of less than 10 microns.

Abstract: A sintered hard metal body (e.g., a cutting insert) is provided as to wear resistance by depositing thereon an intermediate thin coating of a metallic carbide or metallic nitride free from binder metal and applying over this intermediate coating a thin ceramic coating free from binder metal.

Abstract: A method and apparatus of vacuum carburizing by changing the surface chemistry of a metal article through absorption and thermal diffusion of carbon, wherein oxidizing gases and other impurities are initially removed from the chamber in which the metal article is treated by evacuation and the temperature in the chamber is maintained at a level above normal carburizing temperatures, but at a point that is compatible with the physical characteristics of the chamber and the article; whereafter a source of carbon is introduced into the evacuated chamber in accordance with a preselected cycle and at a concentration that is controlled by the absolute pressure of the carbon in the chamber, so that the carbon is absorbed and diffused into the metal article at a controlled rate.