Superalloys

Superalloys are nickel, cobalt or iron-based alloys with elevated temperature strength, creep properties, and oxidation resistance. Nickel, nickel alloys, cobalt, and cobalt alloys are non-ferrous metals with high strength and toughness, excellent corrosion and oxidation resistance, and high to superior temperature strength. Ferrous metals and alloys are based on iron and include carbon steels, alloy steels, stainless steels, cast iron, maraging steel and other specialty iron-based alloys. Clad or bimetal superalloys consist of two different alloys that are bonded integrally together. Metal matrix composites have a composite or reinforced metal or alloy matrix filled with a second component, which may be in particulate, chopped fiber, continuous filament, or fabric form. Other unlisted, specialty or proprietary superalloys are also available. These materials are often based on a unique alloy system, use a novel processing technology, or have properties tailored for specific applications.    

Many superalloys meet the compositional standards of the Unified Numbering System (UNS), a specification established by the American Society for Testing and Materials (ASTM), the Society of Automotive Engineers (SAE), and metal trade associations such as the American Iron and Steel Institute (AISI). The UNS assigns metals and alloys a lettered prefix and a five-digit number. For example, iron-based superalloys belong to the UNS S category and have designations such as UNS S66286. Other standards for superalloys include casting grades, European Norm (EN), American Society of Mechanical Engineers (ASME) standards, and U.S. military specifications (MIL-SPEC). QQ and QQS prefixes are used to designate specific MIL-SPEC metals. 

Suppliers provide superalloys in many stock shapes and forms. Semi-finished stock shapes are suitable for part fabrication by machining, assembly, or other processes. They are also used as feedstock for casting, forging, and spinning. Common stock shapes and forms for superalloys include bars, rods, tubes, plates, profiles, sheets, strips, shims, spheres, foil, wire, billets, slabs, and blooms. Materials are also supplied as billets, ingots, powders, fillers, and reinforcements. Round, hexagonal, coil, and hollow stock are also available. There are two basic types of anodes. Plating anodes are in used in plating or electroplating processes. Sacrificial anodes are used to protect stainless steel or other metal structures from corrosion.    

Selecting refractory and reactive metals requires an analysis of dimensions, production processes, and performance features. Outer diameter (OD), inner diameter (ID), overall length, and overall thickness are important dimensions. Most materials are cast, wrought, extruded, forged, cold-finished, hot-rolled, or formed by compacting powdered metals or alloys. Electric arc furnaces are used to produce very clean metals and alloys with fewer inclusions and lower variability. Performance features for superalloys include resistance to corrosion, heat, wear, shock, and high speeds.

• Cobalt-based Superalloys
  Cobalt-based super alloys are non-ferrous magnetic alloys with high strength and toughness, excellent corrosion and oxidation resistance, and high temperature strength – all key qualities for a...
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• New frontiers in superalloy development
  specializing in inorganic synthesis and characterization, modeling, and radiation science have designed a radical system of experiments to study the science of creating metal and alloy nanoparticles....
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• The Effect Of Shot Peening Coverage On Residual Stress, Cold Work, And Fatigue In A Nickel-base Superalloy (.pdf)
  The goal of this work was to determine effects of shot peening (SP) coverage on the compressive residual stress magnitude, depth, and relaxation of residual stresses due to thermal exposure, as well...
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