A nanoparticle powder is disclosed including a plurality of stabilized nanoparticles having a superalloy composition. At least about 90% of the particles have a convexity between about 0.980-1 and a circularity between about 0.850-1. A method for forming a braze paste is disclosed including mixing the plurality of stabilized nanoparticles with at least one organometallic precursor and up to about 5 wt % binder. A method for modifying an article is disclosed including applying the braze paste to a substrate including at least one crack, removing at least about 70% of the binder in the braze paste, and then applying additional braze paste over the first portion. Under vacuum or inert gas atmosphere, essentially all remaining binder is evaporated. The braze paste is brazed to the article at about 40-60% of the superalloy's bulk liquidus temperature, forming a brazed material and thereby sealing the at least one crack.

An austenitic alloy material is provided that includes a base metal having a surface, and a film containing chromium oxide having a thickness of 0.1 to 50 m on at least one portion of the surface. A chemical composition at a depth position in the film at which the Cr concentration is highest contains, by atom %, 50% or more of Cr as a proportion occupied among components excluding O, C and N. The chemical composition of the base metal consists of, by mass %, C: 0.001 to 0.6%, Si: 0.01 to 5.0%, Mn: 0.1 to 10.0%, P: 0.08% or less, S: 0.05% or less, Cr: 15.0 to 55.0%, Ni: 30.0 to 80.0%, N: 0.001 to 0.25%, O: 0.02% or less, Mo: 0 to 20.0%, Cu: 0 to 5.0%, Co: 0 to 5.0%, W: 0 to 10.0%, Ta: 0 to 6.0%, Nb: 0 to 5.0%, Ti: 0 to 1.0%, B: 0 to 0.1%, Zr: 0 to 0.1%, Hf: 0 to 0.1%, Al: 0 to 1.0%, Mg: 0 to 0.1%, and Ca: 0 to 0.1%, the balance being Fe and impurities.

The present invention provides a heat-resistant alloy and a reaction tube having excellent oxidation resistance, excellent mechanical properties such as tensile ductility, and weldability. A heat-resistant alloy of the present invention comprises, in terms of % by mass, C: 0.35% to 0.7%, Si: more than 0% and 1.5% or less, Mn: more than 0% and 2.0% or less, Cr: 22.0% to 40.0%, Ni: 25.0% to 48.3%, Al: 1.5% to 4.5%, Ti: 0.01% to 0.6%, and the balance being Fe and inevitable impurities, wherein when Pa=11.1+28.1C+29.2Si0.25Ni45.6Ti, and Ya=13.75Al+63.75, Pa<Ya.

A nanoparticle powder is disclosed including a plurality of stabilized nanoparticles having a superalloy composition. At least about 90% of the particles have a convexity between about 0.980-1 and a circularity between about 0.850-1. A method for forming a braze paste is disclosed including mixing the plurality of stabilized nanoparticles with at least one organometallic precursor and up to about 5 wt % binder. A method for modifying an article is disclosed including applying the braze paste to a substrate including at least one crack, removing at least about 70% of the binder in the braze paste, and then applying additional braze paste over the first portion. Under vacuum or inert gas atmosphere, essentially all remaining binder is evaporated. The braze paste is brazed to the article at about 40-60% of the superalloy's bulk liquidus temperature, forming a brazed material and thereby sealing the at least one crack.

To provide a cast product having an alumina barrier layer and method for producing the same. A cast product having an alumina barrier layer of the present invention is a cast product in which an alumina barrier layer containing Al.sub.2O.sub.3 is formed on the surface of a cast body, and the cast body contains C: 0.3 mass % to 0.7 mass %, Si: 0.1 mass % to 1.5 mass %, Mn: 0.1 mass % to 3 mass %, Cr: 15 mass % to 40 mass %, Ni: 20 mass % to 55 mass %, Al: 2 mass % to 4 mass %, rare earth element: 0.005 mass % to 0.4 mass %, W: 0.5 mass % to 5 mass % and/or Mo: 0.1 mass % to 3 mass %, and 25 mass % or more of Fe in the remainder and an inevitable impurity, and 80 mass % or more of the rare earth element is La.

Provided is a heat-resistant and corrosion-resistant high-Cr-containing Ni-based alloy having superior hot forgeability, consisting of, by mass %, 43.1 to 45.5% of Cr, 0.5 to 1.5% of Mo, 0.0001 to 0.0090% of Mg, 0.001 to 0.040% of N, 0.05 to 0.50% of Mn, 0.01 to 0.10% of Si, 0.05 to 1.00% of Fe, 0.01% to 1.00% of Co, 0.01 to 0.30% of Al, 0.04 to 0.3% of Ti, 0.0003 to 0.0900% of V, 0.0001 to 0.0100% of B, 0.001 to 0.050% of Zr, and optionally one or more elements selected from (a) to (d): (a) 0.001 to 0.020% of Cu; (b) 0.001 to 0.100% of W; (c) 0.0001 or more and less than 0.0020% of Ca; and (d) 0.001% or more and less than 0.100% of Nb, and the balance of Ni with inevitable impurities.

Provided is a high strength and high corrosion-resistance Ni-based alloy having excellent hot forgeability, which is suitable for a member for oil drilling, the Ni-based alloy having a composition consisting of, by mass %, 42.1 to 45.5% of Cr, 0.5 to 2.5% of Nb, 1.2 to 2.0% of Ti, 0.0001 to 0.0090% of Mg, 0.001 to 0.040% of N, 0.01 to 0.50% of Mn, 0.001 to 0.050% of Si, 0.01 to 1.00% of Fe, 0.01 to 2.50% of Co, 0.001 to less than 0.500% of Cu, 0.001 to 0.050% of Al, 0.005 to less than 0.100% of V, 0.0001 to 0.0100% of B, 0.001 to 0.050% of Zr, and the balance of Ni with inevitable impurities, and the composition preferably further consists of any one of 0.1 to 1.5% of Mo, 0.1 to 1.5% of W, 0.001 to less than 0.050% of Ca, and 0.001 to less than 0.050% of Ta.

A method for producing a reinforced alloy powder containing a metal matrix in which crystalline oxide particles are dispersed, including: (i) providing a powder mixture including a parent metal powder including a master alloy for forming the metal matrix and an additional powder including an intermediate; (ii) milling the powder mixture by a mechanical synthesis process to make a precursor powder; and (iii) subjecting the precursor powder to a thermal plasma generated by a plasma torch including a plasma gas. The master alloy is iron-based, nickel-based, or aluminum-based. The intermediate is at least one of YFe.sub.3, Y.sub.2O.sub.3, Fe.sub.2O.sub.3, Fe.sub.2Ti, FeCrWTi, TiH.sub.2, TiO.sub.2, Al.sub.2O.sub.3, HfO.sub.2, SiO.sub.2, ZrO.sub.2, ThO.sub.2, and MgO. In (iii), the precursor powder is injected into the plasma torch at a flow rate of 10-30 g/min, a power of the plasma torch is 20-40 kW, and a pressure in a reaction chamber of the plasma torch is 25-100 kPa.

The erosion-prone sections of the tubes in a circulating fluidized bed boiler are provided with a locally thickened sidewall without forming discontinuities on the outer surface of the tubes. This can be accomplished, for example, by replacing the erosion prone portion of the tube with a section having a smaller inside diameter, but the same outside diameter, or by replacing the erosion prone portion of the tube with a section having a thicker sidewall, but the same inside diameter, and smoothing over the outside discontinuity with an alloy coating. A useful alloy coating is also disclosed which can be used for this and other applications.

A low coefficient of thermal expansion high strength alloy and methods of formation thereof, the alloy including: chromium 7 wt. % to 10 wt. %; molybdenum 20 wt. % to 25 wt. %; tungsten 4 wt. % to 7 wt. %; aluminum 0.5 wt. % to 2 wt. %; titanium 0.5 wt. % to 2 wt. %; boron 0.005 wt. % to 0.05 wt. %; niobium 3.9 wt. % tantalum 3.9 wt. % vanadium 0.1 wt. % to 4 wt. %; niobium, tantalum, and vanadium, in combination 0.1 wt. % to 4 wt. %; silicon <0.5 wt. %; zirconium <0.5 wt. %; hafnium <0.5 wt. %; yttrium <0.5 wt. %; copper <0.1 wt. %; manganese <0.1 wt. %; phosphorus <0.1 wt. %; sulfur <0.1 wt. %; iron <5 wt. %; cobalt 15 wt. %; balance nickel, cobalt and nickel, in combination 50 wt. % to 70 wt. %, and aluminum and titanium, in combination 1.4 wt. %.