A method for recycling a Ni-based single crystal superalloy part or unidirectionally solidified superalloy part provided with a thermal barrier coating containing at least a ceramic on a surface of a Ni-based single crystal superalloy substrate or Ni-based unidirectionally solidified superalloy substrate, in which the method including the steps of: melting and desulfurizing a Ni-based single crystal superalloy part or Ni-based unidirectionally solidified superalloy part at a temperature of the melting point or more of the Ni-based single crystal superalloy or Ni-based unidirectionally solidified superalloy and less than the melting point of the ceramic; heating a casting mold for a recycled Ni-based single crystal superalloy part or casting mold for a recycled Ni-based unidirectionally solidified superalloy part to a temperature of the melting point or more of the Ni-based single crystal superalloy or Ni-based unidirectionally solidified superalloy; pouring the desulfurized melted Ni-based single crystal superalloy or Ni-based unidirectionally solidified superalloy into the casting mold, and producing a melting stock or growing a Ni-based single crystal superalloy or Ni-based unidirectionally solidified superalloy; and removing the melting stock or the recycled Ni-based single crystal superalloy part or recycled Ni-based unidirectionally solidified superalloy part from the casting mold. In this way, a method for recycling a Ni-based superalloy part, by which the recycle cost of a Ni-based superalloy part and the lifetime cost of a highly efficient gas turbine engine using a Ni-based superalloy part can be significantly reduced, and further a Ni-based superalloy part having the same high-temperature strength and oxidation resistance as those of a newly produced Ni-based superalloy part can be obtained, is provided.

A ferritic stainless steel material excellent in vibration damping capability has a composition containing, by mass %, from 0.001 to 0.04% of C, from 0.1 to 2.0% of Si, from 0.1 to 1.0% of Mn, from 0.01 to 0.6% of Ni, from 10.5 to 20.0% of Cr, from 0.5 to 5.0% of Al, from 0.001 to 0.03% of N, from 0 to 0.8% of Nb, from 0 to 0.5% of Ti, from 0 to 0.3% of Cu, from 0 to 0.3% of Mo, from 0 to 0.3% of V, from 0 to 0.3% of Zr, from 0 to 0.6% of Co, from 0 to 0.1% of REM, from 0 to 0.1% of Ca, the balance of Fe and unavoidable impurities, and has ferrite single phase matrix with crystal grains of average crystal grain diameter of from 0.3 to 3.0 mm and a residual magnetic flux density of 45 mT or less.

A method for recycling a Ni-based single crystal superalloy part or unidirectionally solidified superalloy part provided with a thermal barrier coating containing at least a ceramic on a surface of a Ni-based single crystal superalloy substrate or Ni-based unidirectionally solidified superalloy substrate, in which the method including the steps of: melting and desulfurizing a Ni-based single crystal superalloy part or Ni-based unidirectionally solidified superalloy part at a temperature of the melting point or more of the Ni-based single crystal superalloy or Ni-based unidirectionally solidified superalloy and less than the melting point of the ceramic; heating a casting mold for a recycled Ni-based single crystal superalloy part or casting mold for a recycled Ni-based unidirectionally solidified superalloy part to a temperature of the melting point or more of the Ni-based single crystal superalloy or Ni-based unidirectionally solidified superalloy; pouring the desulfurized melted Ni-based single crystal superalloy or Ni-based unidirectionally solidified superalloy into the casting mold, and producing a melting stock or growing a Ni-based single crystal superalloy or Ni-based unidirectionally solidified superalloy; and removing the melting stock or the recycled Ni-based single crystal superalloy part or recycled Ni-based unidirectionally solidified superalloy part from the casting mold. In this way, a method for recycling a Ni-based superalloy part, by which the recycle cost of a Ni-based superalloy part and the lifetime cost of a highly efficient gas turbine engine using a Ni-based superalloy part can be significantly reduced, and further a Ni-based superalloy part having the same high-temperature strength and oxidation resistance as those of a newly produced Ni-based superalloy part can be obtained, is provided.

To provide a heat resistant metal gasket that is controlled to have a strength level (ordinary temperature hardness) capable of facilitating processing, and has excellent gas leak resistance. An austenitic stainless steel sheet for a metal gasket, having a chemical composition containing from 0.015 to 0.200% of C, from 1.50 to 5.00% of Si, from 0.30 to 2.50% of Mn, from 7.0 to 17.0% of Ni, from 13.0 to 23.0% of Cr, and from 0.005 to 0.250% of N, all in terms of percentage by mass, containing, as necessary, at least one of Mo, Cu, Nb, Ti, V, Zr, W, Co, B, Al, REM (rare-earth element except for Y), Y, Ca and Mg, with the balance of Fe and unavoidable impurities, having an ordinary temperature hardness of 430 HV or less, having a half width of a peak of an austenite crystal (311) plane in an X-ray diffraction pattern of a cross section perpendicular to a sheet thickness direction of from 0.10 to 1.60, and having a surface roughness Ra of 0.30 mm or less.

A ferritic stainless steel material excellent in vibration damping capability has a composition containing, by mass %, from 0.001 to 0.04% of C, from 0.1 to 2.0% of Si, from 0.1 to 1.0% of Mn, from 0.01 to 0.6% of Ni, from 10.5 to 20.0% of Cr, from 0.5 to 5.0% of Al, from 0.001 to 0.03% of N, from 0 to 0.8% of Nb, from 0 to 0.5% of Ti, from 0 to 0.3% of Cu, from 0 to 0.3% of Mo, from 0 to 0.3% of V, from 0 to 0.3% of Zr, from 0 to 0.6% of Co, from 0 to 0.1% of REM, from 0 to 0.1% of Ca, the balance of Fe and unavoidable impurities, and has ferrite single phase matrix with crystal grains of average crystal grain diameter of from 0.3 to 3.0 mm and a residual magnetic flux density of 45 mT or less.

An austenitic stainless steel sheet contains, on a mass basis, C: 0.04 to 0.11%, Si: 2.0 to 3.5%, Mn: 1.50% or less, Ni: 6.0 to 10.0%, Cr: 12.0 to 15.0%, Mo: 1.3 to 3.2%, Cu: 1.00% or less, N: 0.03 to 0.15%, and O: 0.0050% or less, the balance being Fe and impurities; wherein the austenitic stainless steel sheet has a value of Md.sub.30 of 30.0 to 0 C., wherein the value of Md.sub.30 is represented by the following equation (1):

[00001]$\begin{array}{cc}{\mathrm{Md}}_{30}=551-462\left(C+N\right)-9.2Si-8.1Mn-29\left(Ni+Cu\right)-13.7Cr-18.5Mo& \left(1\right)\end{array}$

in which the symbols of the elements each represents a content (% by mass) of each element. The austenitic stainless steel sheet has a metallographic structure having a content of a strain-induced martensite phase of 30% by volume or more, and has a thickness of 0.15 mm or less.

Problem To provide a heat resistant metal gasket that is controlled to have a strength level (ordinary temperature hardness) capable of facilitating processing, and has excellent gas leak resistance.

Solution An austenitic stainless steel sheet for a metal gasket, having a chemical composition containing from 0.015 to 0.200% of C, from 1.50 to 5.00% of Si, from 0.30 to 2.50% of Mn, from 7.0 to 17.0% of Ni, from 13.0 to 23.0% of Cr, and from 0.005 to 0.250% of N, all in terms of percentage by mass, containing, as necessary, at least one of Mo, Cu, Nb, Ti, V, Zr, W, Co, B, Al, REM (rare-earth element except for Y), Y, Ca and Mg, with the balance of Fe and unavoidable impurities, having an ordinary temperature hardness of 430 HV or less, having a half width of a peak of an austenite crystal (311) plane in an X-ray diffraction pattern of a cross section perpendicular to a sheet thickness direction of from 0.10 to 1.60, and having a surface roughness Ra of 0.30 mm or less.

The invention relates to a method for manufacturing a component, especially of a gas turbine, made of a single crystal (SX) or directionally solidified (DS) nickelbase superalloy, including a heat treatment and a machining and/or mechanical treatment step. The ductility of the component is improved by doing the machining and/or mechanical treatment step prior to said heat treatment and a solution heat treatment of the component is done prior to the machining/mechanical treatment step.

A method to limit surface zone recrystallization in a superalloy article includes limiting recrystallization in a surface zone of a superalloy article by treating the superalloy article in an oxygen-containing environment to introduce oxygen into the surface zone in an amount sufficient to pin any new grain boundaries in the surface zone.