Search Results for infiltration methods

The two most important classes of materials that are manufactured via infiltration methods are copper- and silver-infiltrated refractory metals and refractory carbides, and copper-infiltrated steels. This article focuses on copper-infiltrated steels and discusses the basic requirements for infiltration, which is a technique that is only applicable to material systems that meet certain requirements. It addresses these requirements and describes the conventional (partial) infiltration process of powder metallurgy (PM) steel. The materials used in the process, such as matrix and infiltrant, are discussed. The article also details several criteria used to evaluate the performance of an infiltration process. It concludes with information on alloy steels and fully infiltrated steels.

In general, metal-matrix composites (MMCs) are classified into three broad categories: continuous fiber-reinforced composites, discontinuous or short fiber-reinforced composites, and particle-reinforced composites. This article focuses on stir casting and melt infiltration as the two main methods of MMC solidification processing. It describes the MCC casting methods, such as sand and permanent mold casting, centrifugal casting, compocasting, and high-pressure die casting. The article discusses the MMC infiltration processes in terms of pressure infiltration casting and liquid metal infiltration. It reviews the powder metallurgy processing of aluminum MMCs and deformation processing of discontinuously reinforced aluminum composites. The article concludes with a discussion on the processing of fiber-reinforced aluminum.

This article focuses on the process methods and matrix chemistries of ceramic-matrix composites. These methods include pressure-assisted densification, chemical vapor infiltration, melt infiltration, polymer infiltration and pyrolysis, and sol-gel processing. The article discusses the use of a ceramic, preceramic, or metal phase as a fluid or vapor phase reactant to form the matrix. Emphasis is placed on microstructural features that influence ultimate composite properties.

Metal-matrix composites (MMCs) are a class of materials with a wide variety of structural, wear, and thermal management applications. This article discusses the primary processing methods used to manufacture discontinuous aluminum MMCs, namely, high-pressure die casting, pressure infiltration casting, liquid metal infiltration, spray deposition, and powder metallurgy methods. It describes the processing of continuous fiber-reinforced aluminum, discontinuously, reinforced titanium, and continuous fiber-reinforced titanium. The article concludes with information on work done to develop magnesium, copper, and superalloy MMCs.

Ceramic-matrix composites (CMCs) are being developed for a number of high-temperature and high-performance applications in industrial, aerospace, and energy conservation sectors. This article focuses on processing, fabrication, testing, and characterization methods of CMCs, namely, discontinuously reinforced composites and continuous-fiber-reinforced composites. Processing methods include cold pressing, sintering, hot pressing, reaction bonding, melt infiltration, directed metal oxidation, sol-gel and polymer pyrolysis, self-propagating high-temperature synthesis and joining. A table summarizes the properties of various ceramic reinforcements and industrial applications of these composites.

Electrical contacts are made of elemental metals, composites, or alloys that are made by the melt-cast method or manufactured by powder metallurgy (PM) processes. PM facilitates combinations of metals that ordinarily cannot be achieved by alloying. This article describes the processing, properties, and performance of electrical contacts based on PM or hybrid composite technologies with refractory metals and compounds. These metals and compounds include tungsten, molybdenum, carbide-based composites, and silver-base composites. The article explains composite manufacturing methods, namely, PM methods, internal oxidation, and hybrid consolidation. The availability of the refractory metals and compounds in various product forms are also reviewed.

Electrical contacts are metal devices that make and break electrical circuits. This article describes the property requirements such as electrical conductivity, mechanical properties, chemical properties, fabrication properties, and thermal properties of make-break arcing contacts. The article also focuses on brush contact materials and their interdependence factors for sliding contacts. In addition, the article discusses the properties, manufacturing methods, and applications of electrical contact materials, including wrought materials such as copper metals, silver metals, gold metals, precious metal overlays, tungsten, molybdenum, and aluminum, and composite materials. It concludes by discussing the composite manufacturing methods such as infiltration, press-sinter, press-sinter-repress process, press-sinter-extrude process, internal oxidation, and preoxidized-press-sinter-extrude process, and coprecipitation.

This article describes the various pure forms of carbon matrices and the corresponding methods used to create them or incorporate them into a matrix of a composite. These forms include graphite, diamond, fullerenes, and nanotubes. The article discusses the three types of liquid precursors, namely, thermoplastic, thermosetting, and evaporative or solvent carriers. It provides a description of the advantages and limitations of various methods involved in chemical vapor infiltration. The article concludes with a discussion on matrix contribution to composite properties.

Iron powders are the most widely used powder metallurgy (P/M) material for structural parts. This article reviews low to medium density iron and low-alloy steel parts produced by the pressing and sintering technology. It explains different powder production methods, including Hoeganaes process, Pyron process, atomization of liquid metal, thermal decomposition and the electrodeposition process for carbonyl and electrolytic iron powders. It describes the types of compaction and sintering, explaining their effects of processing with designations. Further, the article deals with the mechanical and physical properties of ferrous P/M materials, which may depend on certain factors, namely microstructure, porosity, density, infiltration, re-pressing, chemical composition, and heat treatment.

This article discusses the characteristics, properties, and production methods of copper powders and copper alloy powders. Bulk of the discussion is devoted to production and applications of powder metallurgy (P/M) parts, including pure copper P/M parts, bronze P/M parts, brass and nickel silver P/M parts, copper-nickel P/M parts, copper-lead P/M parts, copper-base P/M friction materials, copper-base P/M electrical contact materials, copper-base P/M brush materials, infiltrated parts, and oxide-dispersion-strengthened copper P/M materials.

Metal-matrix composites (MMCs) are a class of materials with potential for a wide variety of structural and thermal applications. This article discusses the mechanical properties of MMCs, namely aluminum-matrix composites, titanium-matrix composites, magnesium-matrix composites, copper-matrix composites, superalloy-matrix composites, and intermetallic-matrix composites. It describes the processing methods of discontinuous aluminum MMCs which include casting processes, liquid-metal infiltration, spray deposition and powder metallurgy. The article provides useful information on aluminum MMC designation system and also describes the types of continuous fiber aluminum MMCs, including aluminum/boron MMC, aluminum/silicon carbide MMC, aluminum/graphite MMC, and aluminum/alumina MMC.

This article discusses the solidification of a matrix alloy in cast metal matrix composites (MMCs). It begins with a discussion on the mixing techniques in reinforcement incorporation and wettability of reinforcement. It describes the solidification processes, such as stir mixing and melt infiltration, used in the synthesis of MMCs. The article also considers the fundamentals of the process and presents a computational modeling of particle/solidification front interactions in metal-ceramic systems. The article concludes with information on nanocomposites.

Metal matrix composites (MMCs) can be synthesized by vapor phase, liquid phase, or solid phase processes. This article emphasizes the liquid phase processing where solid reinforcements are incorporated in the molten metal or alloy melt that is allowed to solidify to form a composite. It illustrates the three broad categories of MMCs depending on the aspect ratio of the reinforcing phase. The categories include continuous fiber-reinforced composites, discontinuous or short fiber-reinforced composites, and particle-reinforced composites. The article discusses the two main classes of solidification processing of composites, namely, stir casting and melt infiltration. It describes the effects of reinforcement present in the liquid alloy on solidification. The article examines the automotive, space, and electronic packaging applications of MMCs. It concludes with information on the development of select cast MMCs.

Ceramic-matrix composites (CMCs) have ability to withstand high temperatures and have superior damage tolerance over monolithic ceramics. This article describes important processing techniques for CMCs: cold pressing, sintering, hot pressing, reaction-bonding, directed oxidation, in situ chemical reaction techniques, sol-gel techniques, pyrolysis, polymer infiltration, self-propagating high-temperature synthesis, and electrophoretic deposition. The advantages and disadvantages of each technique are highlighted to provide a comprehensive understanding of the achievements and challenges that remain in this area.

This article provides information on the microstructure of powder metal alloys and the special handling requirements of porous materials. It covers selection, sectioning, mounting, grinding, and polishing, and describes procedures, such as washing, liquid removal, and impregnation, meant to preserve pore structures and keep them open for analysis. The article compares and contrasts the microstructures of nearly 50 powder metal alloys, using them to illustrate the effect of consolidation and compaction methods as well as particle size, composition, and shape. It discusses imaging equipment and techniques and provides data on etchants and etching procedures.

The applications of discontinuously reinforced ceramic-matrix composites (CMCs) fall into four major categories, namely, cutting tool inserts; wear-resistant parts; aerospace and military applications; and other industrial applications, including engines and energy-related applications. This article provides examples for these four categories, with an emphasis on those applications/materials that have achieved commercial viability. The applications for continuous fiber ceramic composites are also summarized.

This article presents a general understanding of causes and possible solutions for defects in the most common metal additive manufacturing (AM) processes: laser powder-bed fusion (L-PBF), laser directed-energy deposition (DED-L), and binder jetting (BJ).