The invention describes a method of heat-treating an article, which includes a first step of heating the article to a temperature of 400° C. to 500° C. at a pressure of 1 to 3 millibar in an atmosphere comprising hydrogen for a period of 0.1 to 50 hours to produce a hot article, a second step of heating the hot article at a temperature of 400° C. to 500° C. at a pressure of 1 to 3 millibar in an atmosphere comprising at least one of hydrogen, argon, and nitrogen, for 0.1 to 50 hours to produce a preliminary heat treated article, and a third step of heating the preliminary heat treated article at a temperature of 400° C. to 500° C. at a pressure of 1 to 3 millibar in an atmosphere comprising at least one of hydrogen, nitrogen, and a hydrocarbon gas, for 0.1 to 50 hours; to produce a heat-treated article.

The invention describes a method of heat-treating an article, which includes a first step of heating the article to a temperature of 400° C. to 500° C. at a pressure of 1 to 3 millibar in an atmosphere comprising hydrogen for a period of 0.1 to 50 hours to produce a hot article, a second step of heating the hot article at a temperature of 400° C. to 500° C. at a pressure of 1 to 3 millibar in an atmosphere comprising at least one of hydrogen, argon, and nitrogen, for 0.1 to 50 hours to produce a preliminary heat treated article, and a third step of heating the preliminary heat treated article at a temperature of 400° C. to 500° C. at a pressure of 1 to 3 millibar in an atmosphere comprising at least one of hydrogen, nitrogen, and a hydrocarbon gas, for 0.1 to 50 hours; to produce a heat-treated article.

A carburizer, which effects carburization with respect to molten iron accommodated in an electric furnace or a ladle, includes a mixture of quicklime and a carbon material having an ash content of from 5 mass % to 18 mass %, and satisfies the conditions 0.6≤(mc+Mc)/ms≤2.7 and 0.7≤(mc+Mc)/ma≤6.5. A method of carburization uses this carburizer. Here, mc represents the mass of CaO in the carbon material, ms represents the mass of SiO.sub.2 in the carbon material, ma represents the mass of Al.sub.2O.sub.3 in the carbon material, and Mc represents the mass of the quicklime.

A carburizer, which effects carburization with respect to molten iron accommodated in an electric furnace or a ladle, includes a mixture of quicklime and a carbon material having an ash content of from 5 mass % to 18 mass %, and satisfies the conditions 0.6≤(mc+Mc)/ms≤2.7 and 0.7≤(mc+Mc)/ma≤6.5. A method of carburization uses this carburizer. Here, mc represents the mass of CaO in the carbon material, ms represents the mass of SiO.sub.2 in the carbon material, ma represents the mass of Al.sub.2O.sub.3 in the carbon material, and Mc represents the mass of the quicklime.

A workpiece made from a self-passivating metal and having one or more surface regions defining a Beilby layer as a result of a previous metal shaping operation is activated for subsequent low temperature gas hardening by exposing the workpiece to the vapors produced by heating a non-polymeric N/C/H compound.

A workpiece made from a self-passivating metal and having one or more surface regions defining a Beilby layer as a result of a previous metal shaping operation is activated for subsequent low temperature gas hardening by exposing the workpiece to the vapors produced by heating a non-polymeric N/C/H compound.

A universal joint or other vehicle driveline assembly includes an inner race, an outer race, and bearings positioned between the races. In some embodiments, the components of the universal joint that are in contact with the bearings are selectively processed to be harder than the other non-contact surfaces of the component.

A universal joint or other vehicle driveline assembly includes an inner race, an outer race, and bearings positioned between the races. In some embodiments, the components of the universal joint that are in contact with the bearings are selectively processed to be harder than the other non-contact surfaces of the component.

A method for producing a surface-hardened material, comprising: an immersion step of immersing an iron steel material having nitrogen attached in the form of a solid solution on the surface thereof in a melt containing a chloride at a temperature ranging from 650° C. to 900° C.; and a cooling step of cooling the immersed iron steel material to a temperature equal to or lower than a martensitic transformation start temperature at a cooling rate equal to or higher than a lower critical cooling rare at which martensitic transformation starts.

A method of treating a surface of a mold. A preliminary treatment of dry-ejecting an angular carbide powder against the surface of the mold so as to cause elemental carbon present within the carbide powder to be diffused into the surface of the mold. The carbide powder has particle diameters not larger than those of a 220 grit and the carbide powder being dry-ejected at an ejection pressure of 0.2 MPa or greater. An after-treatment of dry-ejecting a spherical powder against the surface of the mold to cause the spherical powder to impact the surface of the mold and form innumerable circular arc shaped fine depressions. The spherical powder has a hardness not less than the hardness of a base material of metal of the mold and particle diameters not larger than those of a 220 grit and dry-ejected at an ejection pressure of 0.2 MPa or greater.