Search Results for high-performance austenitic alloys

True alkaline chemicals include caustic soda or sodium hydroxide (NaOH), caustic potash or potassium hydroxide (KOH), and soda ash or sodium carbonate (Na2CO3). This article reviews alkaline chemicals and provides a basis for a general discussion on various alkaline exposures. It describes the corrosion effects of caustic soda on aluminum and aluminum alloys, iron and steel, carbon and low-alloy steels, stainless steels, high-performance austenitic alloys, nickel and nickel alloys, copper and copper alloys, titanium and titanium alloys, and zirconium and zirconium alloys. The article discusses the corrosion effects of caustic soda on nonmetallic materials: plastics, thermoplastics, thermosetting resin materials, carbon and graphite, and ceramics. It concludes with information on the effects of contamination of and by caustic and of admixtures of caustic with other chemicals, including chlorates, chlorides, chlorine/hypochlorite, mercury, sulfur, and iron.

This article describes the microstructure, properties, and performance of carburized steels, and elucidates the microstructural gradients associated with carbon and hardness gradients. It provides information on case depth measurement, the factors affecting case depth, and the formation and causes of microcracks. The article discusses the effects of alloying elements on hardenability, the effects of excessive retained austenite and massive carbides on fatigue resistance, the effects of residual stresses and internal oxidation on fatigue performance of carburized steels. In addition, the causes of intergranular fracture at austenite grain boundaries and their prevention methods are explored. The article also describes the major mechanisms of bending fatigue crack initiation in carburized steels.

This article describes some of the underlying factors of tool steel and bearing steel fractures and appearances. It also briefly introduces the general types of cold work and hot work tool steels and their typical performance requirements. This includes the importance of microstructural conditions achieved with powder metallurgy (PM) tool steels and the need for steel “cleanliness,” especially in preventing contact fatigue in bearings or bending fatigue in gears.

Metallurgical variables, mainly carbon distribution and the presence of nitrogen and metallic phases, can influence the corrosion behavior of austenitic, ferritic, duplex, and martensitic stainless steels. This article describes the effects of these metallurgical and processing variables on the susceptibility of the stainless steels to intergranular corrosion and intergranular stress-corrosion cracking and their testing methods. It explains the effect of sigma and related phases on the corrosion behavior of stainless steels.

Bending fatigue of carburized steel components is a result of cyclic mechanical loading. This article reviews the alloying and processing factors that influence the microstructures and bending fatigue performance of carburized steels. These include austenitic grain size, surface oxidation, retained austenite, subzero cooling, residual stresses, and shot peening. The article describes the analysis of bending fatigue behavior of the steels based on S-N curves that represents a stress-based approach to fatigue. It discusses the types of specimen used to evaluate bending fatigue in carburized steels. The stages of fatigue and fracture of the steels, namely crack initiation, stable crack propagation, and unstable crack propagation, are reviewed. The article analyzes the intergranular fracture at the prior-austenite grain boundaries of high-carbon case microstructures that dominates bending fatigue crack initiation and unstable crack propagation of direct-quenched carburized steels.

This article focuses on the specific features of carbon steels and alloy steels that are pertinent to heating by induction for warm and hot working processes. It provides a detailed account of the effects of various microstructures on austenitization kinetics for AISI 1045 steels. The article explains the factors to be considered for induction heating of various steel alloys. It describes the temperature and compositional issues that should be considered in the forging of steels that are induction heated.

The high-alloyed white irons are primarily used for abrasion-resistant applications and are readily cast into the parts needed in machinery for crushing, grinding, and handling of abrasive materials. This article discusses three major groups of the high-alloy white cast irons: nickel-chromium white irons, chromium-molybdenum irons, and high-chromium white irons. Mechanical properties for three white irons representing each of these three general groups are presented as bar graphs. The article also describes the various heat treatments of a martensitic microstructure, including austenitization, quenching, tempering, annealing, and stress relieving.

High-alloyed white cast irons are an important group of materials whose production must be considered separately from that of ordinary types of cast irons. The metallic matrix supporting the carbide phase in the high-alloy white cast irons can be adjusted by alloy content and heat treatment to develop proper balance between resistance to abrasion and toughness needed to withstand repeated impact. This article provides a brief discussion on the heat treatment, mechanical properties, and chemical compositions of high-alloy white cast irons such as nickel-chromium white irons and high-chromium white irons.

Fabrication of wrought stainless steels requires use of greater power, more frequent repair or replacement of processing equipment, and application of procedures to minimize or correct surface contamination because of its greater strength, hardness, ductility, work hardenability and corrosion resistance. This article provides a detailed account of such difficulties encountered in the fabrication of wrought stainless steel by forming, forging, cold working, machining, heat treating, and joining processes. Stainless steels are subjected to various heat treatments such as annealing, hardening, and stress relieving. Stainless steels are commonly joined by welding, brazing, and soldering. The article lists the procedures and precautions that should be instituted during welding to ensure optimum corrosion resistance and mechanical properties in the completed assembly.

Low-temperature carburization hardens the surface of austenitic stainless steels through the diffusion of interstitial carbon without the formation of carbides. This article provides an overview on austenitic stainless steels and low-temperature carburization. It reviews the competing technologies and commercial application of low-temperature carburization. The article discusses several processing parameters, including activation of the surface, proper surface preparation, selection and condition of the alloy to be carburized, treatment temperature, and carburizing atmosphere for successful low-temperature carburization of austenitic stainless steels and other chromium-containing alloys. It describes the performance properties of the low-temperature carburized layer: fatigue resistance, wear resistance, erosion resistance, and corrosion resistance.

Steels are among the most versatile materials in modifying their microstructure and properties by heat treatment. This article outlines the basic concepts of physical metallurgy relating to the heat treatment of steel. It considers the phases and microstructures of steel together with the transformations observed and critical temperatures during heat treatment. Additionally, the different types of steels, heat treatments, and their purposes are also discussed.

This article reviews the factors influencing carburization to improve wear resistance of steel, such as operating temperature, cost, production volume, types of wear, and design criteria. It details the types of wear, namely abrasive wear and adhesive wear. The article discusses the characteristics of carburized steels that affect wear resistance, including hardness, microstructure, retained austenite, and carbides. It also describes the processing considerations for carburization of titanium.

Tool steels are an important class of steels due to their distinct applications and their specific heat treating issues. This article provides an overview of the classification and production of tool steels, and discusses the procedures and process control requirements for heat treating principal types of tool steels. It reviews the various heat treating processes, namely, normalizing, annealing, stress relieving, austenitizing, quenching, and tempering, and surface treatments and cold treating. The article also provides information on the applicability of these processes to various types of tool steels.

The choice of heat treatment depends on the service requirements of a given bearing and how the bearing will be made. This article describes the design parameters, material characteristics required to sustain performance characteristics, metallurgical properties, and dimensional stability. It also provides a description of various extensively-used heat treatment processes, namely, carburizing, carbonitriding, induction surface hardening, and nitriding associated with various bearings. In addition, the article explores the factors to be considered in selecting a process and explains why it is optimum for a specific application.

This article provides information on the base material properties of wrought duplex stainless steels (DSS). These properties include microstructure, alloy grades, mechanical and physical properties, and corrosion resistance. The article reviews the applications and microstructural development of DSS. It describes the factors influencing welding and weldability of the DSS. These factors include preheating, postweld heat treatment, interpass temperature control, welding practices, welding procedure qualification, filler metal requirements, cracking behavior, and loss of properties. The article examines the applicable welding processes such as fusion welding and solid-state welding processes.

Alloy cast irons are considered to be those casting alloys based on the iron-carbon-silicon system that contain one or more alloying elements intentionally added to enhance one or more useful properties. Alloy cast irons can be classified as white cast irons, corrosion-resistant cast irons, and heat-resistant cast irons. This article discusses abrasion-resistant chilled and white irons, high-alloy corrosion-resistant irons, and medium-alloy and high-alloy heat-resistant gray and ductile irons. The article outlines in a list the approximate ranges of alloy content for various types of alloy cast irons. The article explains the effects of alloying elements and the effects of inoculants. In most cast irons, it is the interaction among alloying elements that has the greatest effect on properties. Inoculants other than appropriate graphitizing or nodularizing agents are used rarely, if ever, in high-alloy corrosion-resistant or heat-resistant irons.

This article discusses the melting and pouring practices, heat treatment, and applications of different types of high-alloy graphitic iron, namely, high-silicon gray irons, high-silicon ductile irons, nickel-alloyed austenitic irons, austenitic gray irons, austenitic ductile irons, and aluminum-alloyed irons.

This article presents a discussion on the melting, pouring, and shakeout practices; composition control; molds, patterns, and casting design; heat treatment; and applications of different classes of nickel-chromium white irons and high-chromium white irons.

Bearing steels, which include high-carbon and low-carbon types, can be divided into service-based classes, such as normal service, high-temperature service, and service under corrosive conditions. This article discusses the importance of matching the hardenability and quenching of a bearing steel. It also discusses the typical microstructure of a high-carbon through-hardened bearing, and shows typical case and core microstructures in carburized bearing materials. Apart from a satisfactory microstructure, which is obtained through the proper combination of steel grade and heat treatment, the single most important factor in achieving high levels of rolling-contact fatigue life in bearings is the cleanliness, or freedom from harmful nonmetallic inclusions, of the steel. Alloy conservation and a more consistent heat-treating response are benefits of using specially designed bearing steels. The selection of a carburizing steel for a specific bearing section is based on the heat-treating practice of the producer, either direct quenching from carburizing or reheating for quenching, and on the characteristics of the quenching equipment.

Hardfacing is defined as the application of a wear-resistant material, in depth, to the vulnerable surfaces of a component by a weld overlay or thermal spray process Hardfacing materials include a wide variety of alloys, carbides, and combinations of these materials. Iron-base hardfacing alloys can be divided into pearlitic steels, austenitic (manganese) steels, martensitic steels, high-alloy irons, and austenitic stainless steel. The types of nonferrous hardfacing alloys include cobalt-base/carbide-type alloys, laves phase alloys, nickel-base/boride-type alloys, and bronze type alloys. Hardfacing applications for wear control vary widely, ranging from very severe abrasive wear service, such as rock crushing and pulverizing to applications to minimize metal-to-metal wear. This article discusses the types of hardfacing alloys, namely iron-base alloys, nonferrous alloys, and tungsten carbides, and their applications and advantages.