Search Results for precipitation-strengthened superalloys

This article provides a discussion on forging methods, melting procedures, forging equipment, forging practices, grain refinement, and critical factors considered in forging process. It describes the different types of solid-solution-strengthened and precipitation-strengthened superalloys, namely, iron-nickel superalloys, nickel-base alloys, cobalt-base alloys, and powder alloys. The article discusses the microstructural mechanisms during hot deformation and presents processing maps for various superalloys. It concludes with a discussion on heat treatment of wrought heat-resistant alloy forgings.

This article covers the current state of materials development of nickel-base superalloys for additive manufacturing (AM) processes and the associated challenges. The discussion focuses on nickel-base superalloy fusion AM processes, providing information on typically encountered cracking mechanisms in AM nickel-base superalloys, such as solid-solution-strengthened nickel-base superalloys and precipitate-strengthened nickel-base superalloys. The mechanisms include solidification cracking, strain-age cracking, liquation cracking, and ductility-dip cracking. The article also provides a short discussion on binder jet AM and powder recyclability.

Superalloys are predominantly nickel-base alloys that are strengthened by solid-solution elements including molybdenum, tungsten, cobalt, and by precipitation of a Ni 3 (Al, Ti) type compound designated as gamma prime and/or a metastable Ni 3 Nb precipitate designated as gamma double prime. This article provides a discussion on the conventional processing, compositions, characteristics, mechanical properties, and applications of powder metallurgy (PM) superalloys. The conventional processing of PM superalloys involves production of spherical prealloyed powder, screening to a suitable maximum particle size, blending the powder to homogenize powder size distribution, loading powder into containers, vacuum outgassing and sealing the containers, and consolidating the powder to full density. PM superalloys include Rene 95, IN-100, LC Astroloy, Udimet 720, N18, ME16, RR1000, Rene 88DT, PA101, MERL 76, AF2-1DA, Inconel 706, AF115, and KM4. The article reviews specialized PM superalloy processes and technical issues in the usage of PM superalloys.

Cobalt is used as an alloying element in alloys for various applications. This article provides a detailed account of the metallurgy of cobalt-base alloys. It focuses on the compositions, properties, and applications of cobalt-base alloys, which include wear-resistant cobalt alloys, heat-resistant cobalt alloys, and cobalt-base corrosion-resistant alloys. The article also describes the heat treatments such as annealing and aging, for these alloys.

Cast nickel-base alloys are used extensively in corrosive-media and high-temperature applications. This article briefly reviews the common types of heat treatments of nickel alloy castings: homogenization, stress relieving, in-process annealing, full annealing, solution annealing, quenching, coating diffusion, and precipitation. It describes the three general strengthening mechanisms, namely, solid-solution hardening, age hardening, and carbide precipitation. The article summarizes the typical heat treatment of the general families of nickel-base castings used in industrial applications. It focuses on the solution treatment and age hardening of cast nickel-base superalloys and the heat treatment of cast solid-solution alloys for corrosion-resisting applications. The article also discusses the typical types of atmospheres used in annealing or solution treating: exothermic, endothermic, dry hydrogen, dry argon, and vacuum.

Superalloys are nickel, iron-nickel, and cobalt-base alloys generally used for high-temperature applications. Superalloys are used in aircraft, industrial, marine gas turbines, nuclear reactors, spacecraft structures, petrochemical production, orthopedic and dental prostheses, and environmental protection applications. This article discusses the material characteristics, phases, structures, and systems of superalloys. It describes the processing of superalloys, including primary and secondary melting, deformation processing (conversion), powder processing, investment casting, and joining methods. The article also describes the properties, microstructure, and thermal exposure of superalloys. It further discusses the effects of environmental factors on superalloys, including oxidation and hot corrosion. Protective coatings are also discussed. The article provides information on the mechanical properties and chemical composition of nickel, iron, and cobalt-base superalloys in both the cast and wrought forms.

This article provides information on nickel alloying elements, and the heat treatment processes of various nickel alloys for applications requiring corrosion resistance and/or high-temperature strength. These processes are homogenization, annealing, solution annealing, solution treating, stabilization treatment, age hardening, stress relieving, and stress equalizing. Discussion of furnaces, fixtures, and atmospheres is included. Nickel alloys used for the heat treatment processes include corrosion-resistant nickel alloys, heat-resistant nickel alloys, nickel-beryllium alloys, special-purpose alloys such as nitinol shape memory alloys, low-expansion alloys, electrical-resistance alloys and soft magnetic alloys. Finally, the article focuses on heat treatment modeling for selecting the appropriate heat treatment process.

Precipitation hardening is a hardening mechanism found in various steels and alloy systems, such as nickel-, cobalt-, titanium-, copper-, and iron-base alloys. This article provides a brief description of precipitation hardening process, furnace equipment, surface-related problems, and protective atmospheres used in heat treatment of iron-base precipitation-hardenable (PH) superalloys. It focuses on various factors to be considered in heat treating of PH stainless steels: cleaning prior to heat treatment, furnace atmospheres, time-temperature cycles, variations in cycles, and scale removal after heat treatment. The article describes the mechanical properties, solution treatment, and aging treatment for many martensitic PH alloys, including: Alloy 17-4 PH, Alloy 13-8 Mo, Alloy 15-5 PH, Custom 450, and Custom 455; as well as semiaustenitic PH stainless steels such as Alloy 17-7 PH, Alloy PH 15-7 Mo, AM-350, Pyromet 350, AM-355, and Pyromet 355; austenitic PH stainless steel, A-286; cast PH stainless steels; and iron-nickel PH superalloys.

The warm and hot working of metals provide the ability to shape important materials into component shapes that are useful in a variety of applications requiring strength, toughness, and ductility. This article focuses on a variety of metals that can be hot or warm worked, and describes the characteristics and processing considerations of each metal. It discusses forging because it is a versatile metalworking process and performed at cold, warm, and hot working temperatures. The article also presents the applications of steels, stainless steels, aluminum alloys, titanium alloys, superalloys, and copper alloys.

The process of making assemblies of solid-solution and precipitation hardening groups of alloys and superalloys often requires welding of dissimilar metals, welding of diffusion-bonded materials, and sometimes weld overlay cladding and even thermal spraying that in turn requires special knowledge and treatments developed specifically for each material. This article emphasizes the special metallurgical welding considerations for welding solid-solution and precipitation hardening nickel alloys, cobalt alloys, and superalloys.

This article discusses fracture, fatigue, and creep of nickel-base superalloys with additional emphasis on directionally solidified and single-crystal applications. It analyzes the physical metallurgy of these alloys. The effects of grain boundary and grain size on failure are summarized. The article also discusses the effects of microstructure and extrinsic parameters on fatigue crack propagation (FCP). It details the modeling of FCP rates and creep and creep-fatigue crack growth rates.

This article discusses the specimen preparation of three types of cast and wrought heat-resistant alloys: iron-base, nickel-base, and cobalt-base. Specimen preparation involves sectioning, mounting, grinding, polishing, and etching. The article illustrates the microstructural constituents of cast and wrought heat-resistant alloys. It describes the identification of ferrite by magnetic etching. The transmission electron microscopy examination of the fine strengthening phases in wrought alloys and bulk extraction in heat-resistant alloys are included. The article also reviews the gamma prime phase, gamma double prime phase, eta phase, laves phase, sigma phase, mu phase, and chi phase in wrought heat-resistant alloys.

This article describes the metallurgy and microstructure of high-performance cobalt-base alloys. It discusses metallographic preparation procedures, including sectioning, mounting, grinding, polishing, etching, staining, and heat tinting. It examines the microstructure of cobalt alloys in cast, wrought, and powder metal forms, including magnetic alloys as well as several cobalt-base superalloys.

This article describes the heat treatment of wrought solid-solution and precipitation-hardening alloys with a focus on the major families of wrought nickel alloys. It also provides information on the heat treatment of some representative solid-solution alloys in the Monel (Ni-Cu), Inconel (Ni-Cr-Mo), Hastelloy (Ni-Mo-Cr), and Incoloy (Ni-Fe-Cr) families of alloys. The heat treatment processes for gamma prime nickel alloys, gamma prime nickel-iron superalloys, and gamma double-prime nickel-iron superalloys are also included. The article also provides information on age-hardenable alloys, and the effects of cold work on aging response and grain growth with examples.

This article describes the different types of precipitation and transformation processes and their effects that can occur during heat treatment of various nonferrous alloys. The nonferrous alloys are aluminum alloys, copper alloys, magnesium alloys, nickel alloys, titanium alloys, cobalt alloys, zinc alloys, and heat treatable silver alloys, gold alloys, lead alloys, and tin alloys. It also provides a detailed discussion on the effects due to precipitation and transformation processes in these non-ferrous alloys.

This article focuses on the properties of conventional wrought superalloys based on nickel, iron, and cobalt, as well as on the properties of alloys produced from powder. The powder metallurgy (P/M) category includes alloys that were originally developed as casting alloys; new alloy compositions developed specifically to benefit from powder processing; and oxide dispersion strengthened alloys (particularly those produced by mechanical alloying). The article discusses some of the applications of superalloys and emphazises the interplay between chemical composition, microstructure, consolidation method, mechanical properties and surface stability of wrought nickel alloys. Vacuum melting processes are a necessity for many nickel- and iron-nickel-base alloys because of the presence of aluminum and titanium as solutes. Cobalt-base alloys do not usually contain these elements and may be melted in air. An appendix to this article presents the property data and corresponding information on a family of cobalt-chromium-tungsten-carbon alloys that use P/M processing.

Directionally solidified (DS) and single-crystal (SX) superalloys and process technology are contributing to significant advances in turbine engine efficiency and durability. These gains are expected to arise from the development of higher creep strength and improved oxidation-resistant SX alloy compositions as well as from the development of SX casting and fabrication technology to utilize advanced transpiration-cooling schemes. This article provides a detailed discussion on the chemistry and castability of first- and second-generation DS and SX superalloys. It summarizes the chemistry modifications applied to MAR-M 247 to develop CMSX-2 with respect to function and objectives. The article also lists the nominal compositions of first- and second-generation DS and SX superalloys.

This article discusses special considerations relative to induction heating of stainless steels and nickel-base superalloys. It focuses on the various industrial and high-temperature applications of induction heating to stainless steel and superalloy components, namely, primary melting processes, preheating for primary and secondary forming processes, heat treatments, brazing, and thermal processing for fusion welds. The article also provides information on computational modeling of induction heating processes for super alloys and stainless steels.

This article briefly introduces the concept of creep properties of additively manufactured (AM) alloys, with a focus on the effects of the characteristic microstructure of AM alloys on creep performance. Relevant postprocessing treatment also is discussed, in relation to improved creep performance based on the improvement of AM initial microstructure.

Heat treating of stainless steel produces changes in physical condition, mechanical properties, and residual stress level and restores maximum corrosion resistance when that property has been adversely affected by previous fabrication or heating. This article focuses on annealing of different types of stainless steels such as austenitic, ferritic, duplex, martensitic, and precipitation-hardening, and on the heat treatment of superalloys and refractory metals. It discusses the recommended procedures for solution annealing, austenite conditioning, transformation cooling, and age tempering of precipitation-hardening stainless steels. The article also lists general recommendations for the annealing temperatures of tantalum, niobium, molybdenum, tungsten, and their alloys.