Powder bed fusion (PBF) of polymers is a collection of additive manufacturing processes that melt and fuse polymer in a powder bed. This article provides a complete suite of materials and processes involved in PBF of polymers. The discussion includes details of thermal and manufacturing issues, and safety, postprocessing, and finishing considerations, as well as of principal defects in PBF polymer parts and the mechanical properties of the parts produced by PBF. The article provides case studies on the applications of polymer PBF.

Material jetting (MJ) is a classification of additive manufacturing processes that involves the selective jetting and subsequent solidification of liquid droplets onto a substrate in a layerwise manner. This article focuses solely on MJ of polymers, providing a process overview and describing the functional characteristics that distinguish it from other AM technologies. It provides information on the properties and design considerations of both build and support materials. Process-related effects on final part properties and overall quality, as well as corresponding design considerations are also covered. The article also discusses the applications and future scope of polymer MJ systems.

Directed-energy deposition (DED) is a kind of additive manufacturing (AM) technology based on synchronous powder feeding or wire feeding. This article provides a comprehensive coverage of DED for ceramic AM, beginning with an overview of DED equipment setup, followed by a discussion on DED materials and the DED deposition process. The bulk of the article is devoted to the discussion on the microstructure and properties of oxide ceramics, namely alumina and zirconia ceramics.

This article is a review of the material extrusion-based ceramic additive manufacturing (MECAM) processes. The discussion begins with details of extrusion with filament and paste, covering the most popular variants of paste extrusion-based MECAM techniques that can be differentiated based on paste type and the method of shape retention of the deposited layer: extrusion freeforming, robocasting ceramic on-demand extrusion, and freeze-form extrusion fabrication. The article then focuses on post-processing considerations and the mechanical properties of sintered ceramic parts. It concludes with information on innovation opportunities in ceramic additive manufacturing, such as incorporating UV-curing and gelation in the process and producing geometrically complex structures from shapeable green bodies.

This article focuses on powder bed fusion (PBF) of ceramics, which has the potential to fabricate functional ceramic parts directly without any binders or post-sintering steps. It presents the results of three oxide ceramic materials, namely silica, zirconia, and alumina, processed using PBF techniques. The article discusses the challenges encountered during PBF of ceramics, including nonuniform ceramic powder layer deposition, laser and powder particle interactions, melting and consolidation mechanisms, optimization of process parameters, and presence of residual stresses in ceramics after processing. The applications of PBF ceramics are also discussed.

The highly irregular morphologies of ceramic powder particles due to their process history present a challenge to binder jetting additive manufacturing (BJ-AM) ceramic powder feedstock processability, but knowledge of powder metallurgy of ceramics benefits the development and analysis of the BJ-AM ceramic processes. Understanding BJ-AM process principles and ceramics processing challenges requires reviewing a number of fundamental principles, which this article delineates. The discussion covers the processability considerations, a brief summary of some fundamental aspects of modeling of liquid permeation in the powder bed, and process capabilities and advantages of BJ-AM technology.

The characterization, testing, and nondestructive evaluation of ceramics and glasses are vital to manufacturing control, property improvement, failure prevention, and quality assurance. This article provides a broad overview of characterization methods and their relationship to property control, both in the production and use of ceramics and glasses. Important aspects covered include the means for characterizing ceramics and glasses, the corresponding rationale behind them, and relationship of chemistry, phases, and microconstituents to engineering properties. The article also describes the effects that the structure of raw ceramic materials and green products and processing parameters have on the ultimate structure and properties of the processed piece. The effects that trace chemistry and processing parameters have on glass properties are discussed. The article describes mechanical tests and failure analysis techniques used for ceramics.

Differential scanning calorimetry (DSC) is the most common thermal technique for polymer characterization. This article provides a detailed account of the various factors and processes involved in DSC. The discussion covers the equipment used, specimen preparation process, calibration requirements, data analysis, and provides examples of the applications and interpretation of DSC.

Adhesive bonding is a proven technology in the manufacture of automotive assemblies, helping carmakers achieve weight reduction goals without compromising body stiffness, crash performance, and noise-vibration-handling characteristics. This article discusses the advantages and limitations of adhesive-bonded aluminum joints and the procedures used to produce them. It addresses surface preparation, the addition of interfacial coatings and primers, and the application of thermoplastic and thermosetting resins. The article examines the nature and role of the various layers that constitute the joint and explains how each contributes to performance. It also discusses adhesive selection factors, joint design, and testing procedures.

This article discusses the fundamentals and operating principles of the following acoustic microscopy methods: scanning laser acoustic microscopy, C-mode scanning acoustic microscopy, and scanning acoustic microscopy. It describes the applications of acoustic microscopy for detecting defects in metals, ceramics, glasses, polymers, and composites with examples.

This article presents a brief discussion on the main applications for low- and high-viscosity polyalphaolefins (PAOs) and highlights key areas of interest and shows why PAOs are used in these applications. It discusses the physical properties of passenger car motor oils (PCMOs) based on or containing PAOs. The properties include Noack volatility and pour point. The article also discusses the properties and applications of heavy-duty engine oil (HDEO), industrial lubricants, food-grade lubricants, greases, transportation gear oils, compressor oils, hydraulic fluids, and transmission fluids.

This article describes two variations of carbon-base coatings: diamondlike carbon (DLC) coatings and polycrystalline diamond (PCD) coatings. It discusses the basics of a few deposition methods as they apply to industrially relevant coatings. The methods include deposition of tungsten-containing hydrogenated amorphous carbon films, deposition of tetrahedral amorphous carbon films, and deposition of silicon-incorporated hydrogenated amorphous carbon films. The most common deposition technologies for diamond films are also discussed. The article provides information on surface preparation for DLC and diamond deposition. It also provides a discussion on the coating composition and structure, mechanical and tribological properties, and applications of DLC and diamond coatings. The quality control techniques for DLC and diamond coatings are specified to meet customer requirements and ensure repeatable quality.

Strategies for the lubrication of mechanical systems operating in extreme environments must exclude the liquid lubricants and greases and rely on alternative methods of lubrication, such as gases and solids. This article provides a survey of some of the more effective alternative methods of lubrication. It provides a discussion on the solid materials that have been most commonly used as lubricants: carbon-base materials, transition metal dichalcogenides, polymers, and soft metals.

This article discusses the importance of friction and wear and the role of lubricants in composites. It highlights the progress and developments in using different forms of carbon allotropes in composites for improved friction and wear performance of materials. The article focuses on the widely used form known as carbon black (CB) and shows how to deal with friction and wear of polymers and composites when gamma irradiation is involved. It also discusses the role of graphite in composite materials, which is widely used as a dry lubricant. The article examines the tribology of carbon nanotubes (CNTs) as components in composite materials. It also highlights some of the most pronounced examples of graphene use as a reinforcement agent for improving tribological performance in composite matrices. The article concludes with a discussion on the progress of research in diamond-containing composites.

Polymers and polymer composites have become attractive for tribological applications due to their specific material properties. This article begins by discussing the fundamentals of polymer friction and wear. It summarizes the main polymer materials used in tribological applications. The article explains the effects of load, sliding velocity, and temperature on the friction coefficient. It describes three types of wear modes, namely, abrasive, adhesion, and fatigue. The article discusses the frictional behavior of polymer composites and polymer coatings. It concludes by providing information on tribotesting of polymers and polymer composites.

This article provides a broad overview of sliding and adhesive wear, its processes, and its control, with special attention to three general classes of materials: metals, ceramics, and polymers. It discusses the ways in which materials can be damaged and removed during sliding contact. The article explains the physical and chemical nature of sliding surfaces. It presents wear equations, design criteria, and criteria for selection of materials. The article also describes the factors that affect wear performance of hybrid sliding systems. It concludes by providing general guidelines to prevent the sliding and adhesive wear in metals, polymers, and ceramics.

This article discusses the adhesion behavior of materials in low-pressure and vacuum environments and provides a schematic illustration of an apparatus for measuring adhesion and friction in ultrahigh vacuum. It describes the effects of low-oxygen pressures and vacuum environments on adhesion and friction, as well as the effects of defined exposure to oxygen on friction. The article discusses the wear of various metals in contact with ceramics, and alloying element effects on friction, wear, and transfer of materials. It also describes studies that characterize the contributions of surface contamination and chemical changes to tribology in low-pressure and vacuum environments.

Abrasive wear is a surface-damage process with material loss caused by hard asperities or abrasive particles occurring when two surfaces are sliding against each other. There are two types of abrasive wear: two-body abrasion and three-body abrasion. This article discusses the abrasive wear mechanism in ductile materials and commonly used testers for evaluating the resistance of materials to abrasive wear. The testers include pin-on-disk, block-on-ring, block-on-drum, and dry sand/rubber wheel abrasion tester. The article reviews the abrasion resistance of metallic materials, ceramic materials, and polymeric materials. It discusses factors that influence abrasive wear, including the environment, hardness, toughness, microstructure, and lubrication.

Current understanding of polishing wear involves a combination of abrasive, plastic flow, and tribochemical wear. This article explains these mechanisms and the correlation between them. Some explanations about practical polishing wear control, applications, and future prospects are also given. This article discusses the influence of size and number of wear particles on polishing at three abrasive wear modes. These include cutting, wedge forming, and plowing. The article concludes with information on applications and prospects of polishing wear control.

This article discusses the functions of lubricants to prevent premature failure of rolling element bearings and the advantages of fluid lubrication. It describes the composition of refined mineral oil for rolling bearing applications. The article reviews the types and properties of nonpetroleum oils, such as polyglycols, phosphate esters, silicone fluids, dibasic acid esters, and fluorinated polyethers. It discusses the properties of greases, including grease speed limits, grease composition, relubrication intervals, corrosion prevention behavior, and grease compatibility. The article concludes with a discussion on polymeric lubricants and solid lubricants.