This article addresses consumable selection and procedure development for the welding of stainless steels. The WRC-1992 diagram and the Schaeffier diagram, are used to illustrate the rationale behind many filler-metal choices. The article discusses the basic metallurgy and base metals of five major families of stainless steels: martensitic stainless steels, ferritic stainless steels, austenitic stainless steels, precipitation-hardening (PH) stainless steels, and duplex ferritic-austenitic stainless steels. Stainless steels of all types are weldable by virtually all welding processes. The article describes the common arc welding processes with regard to procedure and technique errors that can lead to loss of ferrite control with the common austenitic stainless steel weld metals that are designed to contain a small amount of ferrite for protection from hot cracking. The arc welding processes include shielded-metal arc welding, gas-tungsten arc welding, and gas-metal arc welding.

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.

Repair and maintenance of parts and components is carried out as a logical procedure that ensures the production of a usable and safe component or it can be approached haphazardly. This article describes the requirements and repair techniques of arc and oxyfuel welding processes to repair weld defects and structural failures. It further discusses the preliminary assessment and base-metal preparation involved in weld repair. Furthermore, the article provides information on the general repair guidelines that are followed to ensure successful weld repairs of both ferrous (carbon steels, cast irons, and stainless steels) and nonferrous (titanium) base metals.

Weldments exhibit special microstructural features that need to be recognized and understood in order to predict acceptable corrosion service life of welded structures. This article describes some of the general characteristics associated with the corrosion of weldments. It emphasizes the role of macrocompositional and microcompositional variations to bring out differences that need to be realized in comparing corrosion of weldments to that of wrought materials. The article concludes with a discussion on important welding practices used to minimize corrosion in weldments.

This article reviews the influence of local strains and corrosion fatigue on the initiation of fatigue cracks in duplex stainless steels. It provides useful information on fatigue crack growth, fatigue strength, and fracture toughness of duplex stainless steels. The article discusses the fatigue and fracture behavior of duplex stainless steels during stress-corrosion cracking. It details the elevated-temperature properties of duplex stainless steels, such as creep-fatigue behavior and thermal cycling properties.

Stainless steels are an important class of engineering alloys used in both wrought and cast form for a wide range of applications and in many environments. This article aids in the selection of stainless steels based on weldability and service integrity. Stainless steels are classified by microstructure and are described as ferritic, martensitic, austenitic, or duplex. The article illustrates compositional ranges of the ferritic, martensitic, austenitic, and duplex alloys in the Schaeffler diagram. It describes the metallurgical aspects of welded stainless steels to be considered for particular engineering applications and service conditions. The article discusses the microstructural evolution of the weld metal and the heat-affected zone, susceptibility to defect formation during welding, mechanical and corrosion properties, and weld process tolerance.

Stainless steel alloys have many unique failure mechanisms, including environmentally assisted cracking, cracking associated with welding, and secondary phase embrittlement. This article describes these failure mechanisms and the fracture modes associated with the different categories of stainless steel. These mechanisms and modes are grouped together because of their similarities across the categories.

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.

This article provides information on the metallurgy of austenitic stainless steels, and the formation of their intermediate phases (Sigma, Chi, and Laves). It discusses sensitization, a major problem associated with the austenitics, and solutions to avoid the problem. The article describes heat treatments applied to austenitic stainless steels, namely, soaking for homogenization and preparation for hot working; annealing to remove the effects of cold work and to put alloying elements into solid solution; and stress relieving. It provides information on the stabilizing anneal process, which is conducted on stabilized alloys, and discusses the metallurgical characteristics of austenitic stainless steels that may affect the selection of a stress-relieving treatment and prevention of stress corrosion by stress relieving. The article also discusses the heat treatments applied to duplex stainless steels, which involve soaking and annealing, achieving the austenite-ferrite balance, precipitation of intermetallics, and alpha prime precipitation.

Cast stainless steels are usually specified on the basis of composition by using the alloy designation system established by the Alloy Casting Institute. This article discusses the corrosion behavior of heat-resistant alloys due to oxidation, sulfidation, and carburization. It describes the influence of the metallurgy of corrosion-resistant stainless steels on general corrosion, intergranular corrosion, localized corrosion, corrosion fatigue, and stress corrosion.

Stainless steels are iron-base alloys containing minimum of approximately 11% Cr, and owing to its excellent corrosion resistance, are used for wide range of applications. These applications include nuclear reactor vessels, heat exchangers, oil industry tubular, chemical processing components, pulp and paper industries, furnace parts, and boilers used in fossil fuel electric power plants. The article provides a brief introduction on corrosion resistance of wrought stainless steel and its designations. It lists the chemical composition and describes the physical and mechanical properties of five major stainless steel families, of which four are based on the crystallographic structure of the alloys, including martensitic, ferritic, austenitic, or duplex. The fifth is precipitation-hardenable alloys, based on the type of heat treatment used. The article further discusses the factors in the selection of stainless steel, namely corrosion resistance, fabrication characteristics, product forms, thermally induced embrittlement, mechanical properties in specific temperature ranges, and product cost.

This article describes metallographic preparation and examination techniques for stainless steels and maraging steels. It presents a series of micrographs demonstrating microstructural features of these alloys. Procedures used to prepare stainless steels for macroscopic and microscopic examination are similar to those used for carbon, alloy, and tool steels. Cutting and grinding must be carefully executed to minimize deformation because the austenitic grades work harden readily. The high-hardness martensitic grades that contain substantial undissolved chromium carbide are difficult to polish while fully retaining the carbides. Unlike carbon, alloy, and tool steels, etching techniques are more difficult due to the high corrosion resistance of stainless steels and the various second phases that may be encountered. The microstructures of stainless steels can be quite complex. Matrix structures vary according to the type of steel, such as ferritic, austenitic, martensitic, precipitation hardenable, or duplex.

This article reviews the properties of cast steels that are specified for liquid corrosion service at temperatures above and below 650 deg C. Stainless steel castings are usually classified based on their resistance to corrosion and heat and generally fall into one category or the other. The article describes alternate methods for classifying cast stainless steels, one is based on grade designations, the other on microstructural analysis. It also addresses heat treatment, pointing out its similarities with the thermal processing of wrought materials, and establishes the importance of mechanical properties in material selection. The article presents information on the selection process and provides a detailed list of heat-resistant cast steels and alloys. It also includes key manufacturing characteristics to aid in foundry and welding-related decisions.

Stainless steels are primarily alloys of iron and chromium. They are grouped into five families, primarily based on their microstructure: ferritic, austenitic, martensitic, duplex, and precipitation hardening. Three out of the five families of stainless steels, namely, austenitic, ferritic, and martensitic, are well suited for manufacture via conventional powder metallurgy (PM) processes. This article presents the iron-chromium partial phase diagram to illustrate the changes in the temperature range when pure iron is alloyed with chromium. It describes AISI and UNS numbering systems, which are used as an identification system for stainless steels. The article tabulates the material designations of stainless steels in accordance with the Metal Powder Industries Federation. It also details the characteristics and chemical composition of wrought and PM stainless steels.

Penetration-enhanced gas tungsten arc welding (GTAW) processes have been referred to variously as flux tungsten inert gas (TIG), A-TIG, and GTAW with a penetration-enhancing compound. This article provides a discussion on the principles of operation, advantages, disadvantages, procedures, and applications of GTAW. It also includes information on the equipment used and health and safety issues associated with GTAW.

Stainless steels are characterized as having relatively poor wear resistance and tribological properties, but they are often required for a particular application because of their corrosion resistance. This article describes the classification of stainless steels and wear. Stainless steels have been classified by microstructure and are categorized as austenitic, martensitic, ferritic, or duplex. The main categories of wear are related to abrasion, erosion, adhesive wear, and surface fatigue. The article presents a list that proposes the alloy family that could be the optimal selection for a particular wear mode. The corrosion modes include dry sliding, tribocorrosion, erosion, erosion-corrosion, cavitation, dry erosion, erosion-oxidation, galling and fretting.

Stainless steels are essential for the modern industrial civilization because of their corrosion resistance, especially in the chemical, petrochemical, and food industries. This article discusses the classification of the various types of stainless steels, including martensitic, ferritic, austenitic, duplex (ferritic-austenitic), and precipitation-hardening stainless steels. It presents a checklist of characteristics to be considered in selecting the proper type of stainless steel for a specific application. The article also outlines the need to promote the formation of an effective protective passive layer in stainless steels. It discusses hardness, fatigue and fretting properties, tribological properties, wear resistance, and corrosion-wear process of the S-phase layer. The article describes two thermochemical nitriding techniques of stainless steels: plasma-assisted nitriding techniques and non-plasma assisted nitriding processes. It also describes the difficulties in stainless steel nitriding/carburizing.