This article describes the physical properties of powder metallurgy (PM) stainless steels. These include thermal diffusivity, conductivity, thermal expansion coefficient, Poisson's ratio, and elastic modulus. The article contains a table that lists the characteristics of various grades of PM stainless steels. It discusses the applications of various PM stainless steels such as rearview mirror brackets, anti-lock brake system sensor rings, and automotive exhaust flanges and sensor bosses.

This article describes the factors influencing the room-temperature and elevated-temperature mechanical properties of powder metallurgy (PM) stainless steels. It contains tables that list the mechanical property specifications of the Metal Powder Industries Federation (MPIF) Standard 35.

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.

This article provides a detailed discussion on the most commonly employed tests and specific examples of the use of these tests in evaluating the corrosion resistance of powder metallurgy (P/M) stainless steels. It describes the influence of various processing parameters on the corrosion resistance of P/M stainless steels. The approaches used to improve the corrosion resistance of sintered stainless steels are discussed briefly. The article also presents a discussion on the manufacturing and corrosion characteristics of P/M superalloys.

This article reviews various test methods used for evaluating the corrosion resistance of powder metallurgy stainless steels. These include immersion testing, salt spray testing, and electrochemical testing. The article discusses the factors that affect corrosion resistance of sintered stainless steels: compaction-related factors, sintering-related factors, and effects of alloy composition. Corrosion resistance data for sintered stainless steels is provided.

Metallic alloys that are typically used for medical purposes include stainless steels, Ti-6Al-4V, and Co-Cr-Mo. This article discusses the relative merits of each of these alloys. The utilization of stainless steels in the biomedical industry, especially in relation to the additive manufacturing (AM) process, is the main focus of this article. The characteristics of various stainless steels are described subsequently, and the categories that are of relevance to the biomedical industry are identified. The types of stainless steels covered are austenitic, ferritic, martensitic, duplex, and precipitation-hardened stainless steels. The article discusses the potential benefits of AM for biomedical devices. It describes the types of AM processes for stainless steels, namely binder jet, directed-energy deposition, and laser powder-bed fusion. The article reviews the AM of austenitic, martensitic, and PH stainless steels for biomedical applications. In addition, the challenges and obstacles to the clinical use of AM parts are covered.

Powder metallurgy (PM) stainless steels, as with conventional PM steels, are often used in the as-sintered condition. In addition to cost considerations, minimization of postsinter handling and secondary operations is also preferred because it reduces the potential for contamination of the parts with particulates and residues, which can result in the appearance of surface rust. This article provides information on various secondary operations, including tumbling, re-pressing, resin impregnation, annealing or heat treating, brazing, machining, and welding. It describes those aspects relating to welding of PM stainless steels, specifically, the effects of density, residual porosity, and sintered chemistry on weldability. Further, the article investigates the influence the sintering atmosphere has on machinability, as well as differences created by the presence of residual porosity.

This article provides a general overview of additively manufactured steels and focuses on specific challenges and opportunities associated with additive manufacturing (AM) stainless steels. It briefly reviews the classification of the different types of steels, the most common AM processes used for steel, and available powder feedstock characteristics. The article emphasizes the characteristics of the as-built microstructure, including porosity, inclusions, and residual stresses. It also reviews the material properties of AM steel parts, including hardness, tensile strength, and fatigue strength, as well as environmental properties with respect to corrosion resistance, highlighting the importance of postbuild thermal processing.

Stainless steels are used for medical implants and surgical tools due to the excellent combination of properties, such as cost, strength, corrosion resistance, and ease of cleaning. This article describes the classifications of stainless steels, such as austenitic stainless steels, martensitic stainless steels, ferritic stainless steels, precipitation-hardening stainless steels, and duplex stainless steels. It contains a table that lists common medical device applications for stainless steels. The article discusses the physical metallurgy and physical and mechanical properties of stainless steels. Medical device considerations for stainless steels, such as fatigue strength, corrosion resistance, and passivation techniques, are reviewed. The article explains the process features of implant-grade stainless steels, including type 316L, type 316LVM, nitrogen-strengthened, ASTM F1314, ASTM F1586, ASTM F2229, and ASTM F2581 stainless steels.

This article describes the sintering behavior of austenitic, ferritic, and martensitic stainless steels. It presents different sintering schedules that are selected by Metal Powder Industries Federation (MPIF). The article provides information on the equipment and atmospheres used for sintering and the steps involved in the process. It discusses the factors that influence the dimensional changes in sintering, namely, powder-related, compaction-related, and sintering-related factors.

This article provides information on the process details that differ from general water atomization of metals as they relate to basic and engineering properties that are specific to stainless steel powders. The discussion focuses on the compacting-grade stainless steel powders. The process details include raw materials, melting method, and control of physical and chemical powder characteristics. The article describes the gas atomization of stainless steel powders and processes that are done after water atomization: drying, screening, annealing, and lubricating. It also discusses the two types of quality assurance testing measures for powder metallurgy stainless steels: tests for powder contamination and tests of chemical and physical properties.

Stainless steel powder metallurgy (P/M) parts represent an important and growing segment of the P/M industry. This article describes the processing, properties, and composition of medium-density and high-density P/M stainless steels. Medium-density materials are processed by pressing and sintering prealloyed stainless powders. High-density materials are produced by hot isostatic pressing, cold isostatic pressing followed by extrusion, or metal injection molding. The comparison of mechanical properties of these P/M stainless steels is represented graphically. The article contains a table that lists the effect of iron, carbon, nitrogen, oxygen, and density on the corrosion resistance of the sintered austenitic stainless steels.

This article discusses the corrosion characteristics of superaustenitic stainless and duplex stainless steels, which are used in pharmaceutical industry. It describes passivation treatments and the electropolishing of stainless steels. The article informs that electropolishing is not a passivation treatment, although the proper execution of the process will result in a passive surface. The article concludes with a discussion on roughing, which is a phenomenon of particular interest to the pharmaceutical industry.

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.

Cryogenic temperatures cause many structural alloys to become brittle, which is an unacceptable condition in most structural applications and is rectified by optimizing the weld composition. Although nonmatching weld compositions are most appropriate, differences between the welds and parent material in terms of thermal contraction, corrosion, and other factors must be considered. This article discusses these differences and describes the effect of these factors on the choice of the weld filler metal. It also provides a detailed discussion on the effects of cryogenic services on mechanical properties of the parent metal.

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.

Additive manufacturing (AM) is a highly desired layer-by-layer fabrication process capable of creating near-net-shaped three-dimensional components for a wide range of industries, such as the automotive and aerospace industries. This article focuses on aluminum, titanium, and stainless steel alloys that are commonly used or highly desired for use with AM due to their widespread applicability and favorable mechanical properties. It presents an overview of two of the major AM processes: powder-bed and powder-fed. The article discusses processability using AM. It also provides an overview of material microstructures, defects, and the impact on mechanical behaviors.

This article briefly describes the welding of various stainless steels to dissimilar steels. The stainless steels include austenitic stainless steels, ferritic stainless steels, and martensitic stainless steels. The dissimilar steels include carbon and low-alloy steels. In addition, the article provides information on the cladding of austenitic stainless steel to carbon or low-alloy steels.

This article discusses two categories of stainless steel casting alloys and their nomenclature. It provides information on two situations in which welding of stainless steel castings is required. These situations are based on casting defects and selection of welding processes. The article presents compositions and typical microstructures of corrosion-resistant stainless steel casting alloys in tabular form. It presents special considerations for the welding of martensitic stainless steel castings. The article reviews the two most serious problems encountered in the welding of stainless steel castings, namely, solidification hot cracking and heat-affected zone hot cracking. It concludes with a discussion on the some useful considerations for welding corrosion-resistant alloys to avoid defects.

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.