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 for reinforcing a steel component, having a carbonitriding step providing a first substep of case-hardening, and a second substep of nitriding, the first and second substeps of case-hardening and of nitriding of the step of carbonitriding the component are performed in one and the same heat treatment cycle.

A microstructure may be provided by forming a metal layer such as a molybdenum layer over a substrate. An aluminum nitride layer is formed on a top surface of the metal layer. A surface portion of the aluminum nitride layer is converted into a continuous aluminum oxide-containing layer by oxidation. A dielectric spacer layer may be formed over the continuous aluminum oxide-containing layer. Contact via cavities extending through the dielectric spacer layer, the continuous aluminum oxide-containing layer, and the aluminum nitride layer and down to a respective portion of the at least one metal layer may be formed using etch processes that contain a wet etch step while suppressing formation of an undercut in the aluminum nitride layer. Contact via structures may be formed in the contact via cavities. The microstructure may include a micro-electromechanical system (MEMS) device containing a piezoelectric transducer.

A microstructure may be provided by forming a metal layer such as a molybdenum layer over a substrate. An aluminum nitride layer is formed on a top surface of the metal layer. A surface portion of the aluminum nitride layer is converted into a continuous aluminum oxide-containing layer by oxidation. A dielectric spacer layer may be formed over the continuous aluminum oxide-containing layer. Contact via cavities extending through the dielectric spacer layer, the continuous aluminum oxide-containing layer, and the aluminum nitride layer and down to a respective portion of the at least one metal layer may be formed using etch processes that contain a wet etch step while suppressing formation of an undercut in the aluminum nitride layer. Contact via structures may be formed in the contact via cavities. The microstructure may include a micro-electromechanical system (MEMS) device containing a piezoelectric transducer.

The steel material for a carburized bearing part according to the present invention contains, by mass %, C: 0.25 to 0.45%, Si: 0.15 to 0.45%, Mn: 0.40 to 1.50%, P: 0.015% or less, S: 0.005% or less, Cr: 0.60 to 2.00%, Mo: 0.10 to 0.35%, V: 0.20 to 0.40%, Al: 0.005 to 0.100%, Ca: 0.0002 to 0.0010%, N: 0.0300% or less and O: 0.0015% or less, with the balance being Fe and impurities, and satisfies Formulae (1) to (3).
1.20<0.4Cr+0.4Mo+4.5V<2.75  (1)
A1/A2>0.50  (2)
2.7C+0.4Si+Mn+0.45Ni+0.8Cr+Mo+V>2.55  (3)
Formula (2) shows an area fraction of sulfides containing Ca in an amount of 1 mol % or more among sulfides having an equivalent circular diameter of 1 μm or more.

Metal powder is compacted in a die to produce a preform having a preselected porosity with the metal powder containing iron and having a plurality of particles having a preselected particle sizes. The preform is carburized to produce a high carbon solution in the metal powder. The preform is contacted with an ammonia gas distillation solution to inject nitrogen therein. The preform is heat treated for a predetermined period of time at a predetermined temperature and at a predetermined pressure. The preform is quenched to form a metal part.

Metal powder is compacted in a die to produce a preform having a preselected porosity with the metal powder containing iron and having a plurality of particles having a preselected particle sizes. The preform is carburized to produce a high carbon solution in the metal powder. The preform is contacted with an ammonia gas distillation solution to inject nitrogen therein. The preform is heat treated for a predetermined period of time at a predetermined temperature and at a predetermined pressure. The preform is quenched to form a metal part.

Methods for treating steel, along with the resulting treated steel, are provided. The method may comprise: nitriding a carburized Ferrium steel component such that the Ferrium steel component has a surface portion with a nitrogen content that is greater than 0% to about 5% by weight. Nitriding the Ferrium steel component may increase the surface hardness of the Ferrium steel. The surface portion may have a nitrogen content of about 0.05% to about 0.5% by weight.

Methods for treating steel, along with the resulting treated steel, are provided. The method may comprise: nitriding a carburized Ferrium steel component such that the Ferrium steel component has a surface portion with a nitrogen content that is greater than 0% to about 5% by weight. Nitriding the Ferrium steel component may increase the surface hardness of the Ferrium steel. The surface portion may have a nitrogen content of about 0.05% to about 0.5% by weight.

A damper spring having an excellent fatigue limit is provided. A damper spring according to the present embodiment includes a nitrided layer formed in an outer layer, and a core portion that is further inward than the nitrided layer. The chemical composition of the core portion consists of, in mass%, C: 0.53 to 0.59%, Si: 2.51 to 2.90%, Mn: 0.70 to 0.85%, P: 0.020% or less, 5: 0.020% or less, Cr: 1.40 to 1.70%, Mo: 0.17 to 0.53%, V: 0.23 to 0.33%, Cu: 0.050% or less, Ni: 0.050% or less, Al: 0.0050% or less, Ti: 0.050% or less, N: 0.0070% or less, and Nb: 0 to 0.020%, with the balance being Fe and impurities. In the core portion, a number density of V-based precipitates having a maximum diameter ranging from 2 to 10 nm is 500 to 8000 pieces/μm.sup.2.