This article provides a high-level overview of thermal spray technologies and their applications and benefits. It is intended to educate members of government, industry, and academia to the benefits of thermal spray technology. The article describes the value of thermal spray technology with examples of application success stories. A few applications critical to thermal spray and market growth are briefly discussed. The article also summarizes the key research areas in thermal spray technology.

This article provides a brief description of commercially important thermal spray processes and gives examples of applications and application requirements. The processes covered are flame, wire arc, plasma, high-velocity oxyfuel processes, detonation gun, and cold spray methods. Examples are provided of the applications in aerospace, automotive, and medical device industries as well as the use of thermal spray as an additive manufacturing technique.

This article summarizes the results of work completed by the ASM Thermal Spray Society Advisory Committee to identify key research challenges and opportunities in the thermal spray field. It describes and prioritizes research priorities related to emerging process methods, thermal spray markets and applications, and process robustness, reliability, and economics.

This article presents best practices for the metallographic preparation of specimens produced via thermal spray coating methods. It outlines typical metallographic preparation process flow, highlighting important considerations for obtaining a clear and representative specimen suitable for characterization via examination techniques, such as optical or electron microscopy. The process flow includes preliminary resin infiltration, sectioning, mounting, grinding, and polishing. To aid in the identification and resolution of common issues during subsequent specimen analysis, the article presents common issues, along with causes and mitigation strategies. It describes the processes involved in the interpretation of the thermal spray coating microstructure.

Thermal barrier coatings (TBCs) are applied using thermal spray coating (TSC) processes to components that are internally cooled and operated in a heated environment. The TSC microstructures are prone to interactions with common metallographic procedures that may result in artifacts and misinterpretation of the TSC microstructure. This article aims to aid in identifying metallographic TSC artifacts, specifically in the air plasma spray zirconia-based TBC, including both of its common constituents, the bond coating and the top coating. Artifacts that result from specific sectioning and mounting practices, as well as from different polishing times, are presented. Additionally, the article discusses the factors in optical microscopy and scanning electron microscopy that affect microstructure interpretation.

Abradable coatings (such as Ni-4Cr-4Al/bentonite) are used throughout jet engines, primarily as sacrificial coatings into which moving components wear. This article presents the Accepted Practice for sample preparation of abradable coatings for metallographic analysis, based on round robin testing by several laboratories.

Molybdenum thermal spray coatings are used in aerospace and other industries for wear resistance applications. Metallographic sample preparation of molybdenum coatings presents unique challenges. The purpose of the investigation described in this article is to determine Accepted Practices for sample preparation to better understand the process related microstructures of thermal spray molybdenum powders. The committee followed a round robin approach to assess metallographic sample preparation by a variety of laboratories. The article summarizes the results of the committee’s work.

This article, prepared under the auspices of the ASM Thermal Spray Society Committees on Accepted Practices, describes a procedure for evaluating residual stresses in thermal spray coatings, which is an extension of the well-known layer removal method to include the Young’s modulus and Poisson’s ratio properties of the thermal spray coating material and the substrate. It presents questions and answers that were selected to introduce residual stresses in thermal spray coatings. The article describes equipment and the laboratory procedure for the modified layer removal method and provides the description of the residual stress specimen. It also describes the procedures for applying or installing bonded resistance strain gages, the dimensions of the test specimen, the procedure for removing layers, and the method for interpreting the data to evaluate residual stresses. The spreadsheet program, “ MLRM for Residual Stresses ,” is available as a supplement to this document.

This article addresses critical aspects in bond testing of thermal spray coatings and provides step-by-step guidance for obtaining representative and reproducible test results based on ASTM C633 and other applicable industry standards. It clarifies details of ASTM C633 requirements and provides examples of the best practice confirmed by hundreds of tests performed worldwide, adopted by numerous industrial standards, and requested to comply with international technical standardization and certification organizations such ISO, AS, SAE, and Nadcap.

Product design requires an understanding of the mechanical properties of materials, much of which is based on tensile testing. This chapter describes how tensile tests are conducted and how to extract useful information from measurement data. It begins with a review of the different types of test equipment used and how they compare in terms of loading force, displacement rate, accuracy, and allowable sample sizes. It then discusses the various ways tensile measurements are plotted and presents examples of each method. It examines a typical load-displacement curve as well as engineering and true stress-strain curves, calling attention to certain points and features and what they reveal about the test sample and, in some cases, the cause of the behavior observed. It explains, for example, why some materials exhibit discontinuous yielding while others do not, and in such cases, how to determine when yielding begins. It also explains how to determine other properties via tensile tests, including ductility, toughness, and modulus of resilience.

This appendix provides readers with worked solutions to 25 problems involving calculations associated with tensile testing and the determination of mechanical properties and variables. The problems deal with engineering factors and considerations such as stress and strain, loading force, sample lengthening, and machine stiffness, and with mechanical properties and parameters such as elastic modulus, Young’s modulus, strength coefficient, strain-hardening exponent, and modulus of resilience. They also cover a wide range of materials including various grades of aluminum and steel as well as iron, titanium, brass, and copper alloys.

The mechanical behavior of a material, in the most practical sense, is how it deforms or breaks under load; in other words, how it responds when stressed. This chapter provides a brief review of the properties associated with mechanical behavior, including stress, strain, elasticity, plastic deformation, ductility, hardness, creep, fatigue, and fracture. It also describes the primary components of a Charpy impact tester and the role they serve.

This chapter provides an overview of the various inspection methods used with metals and alloys, namely visual inspection, coordinate measuring machines, machine vision, hardness testing, tensile testing, chemical analysis, metallography, and nondestructive testing. The nondestructive testing methods discussed are liquid penetrant inspection, magnetic particle inspection, eddy current inspection, radiographic inspection, and ultrasonic testing.

Visual inspection is the most important method of inspection of materials. This chapter describes the procedures involved in visual inspection such as identification markings, identification of defects caused by heating problems, scaling of materials, cracking characterization, and measurement of material dimensions. It discusses the mechanisms, advantages, limitations, components, and applications of various visual inspection tools, namely magnifying devices, lighting for visual inspection, measuring devices, miscellaneous measuring equipment, record-keeping devices, and macroetching.

The coordinate measuring machine (CMM) is used for three-dimensional inspection of both in-process and finished parts. This chapter provides a detailed account of the operating principles, measurement techniques, capabilities, and applications of CMMs. The types of CMMs are described. Vertical CMMs include cantilever-type, bridge-type, and gantry CMMs; horizontal CMMs, such as the horizontal-arm type, are also covered. The CMM application for geometric measurement, contour measurement, and specialized surface measurement are discussed.

Machine vision is a means of simulating the image recognition and analysis capabilities of the human eye/brain system with electronic and electromechanical techniques. This chapter discusses four basic steps in the machine vision process, namely image formation, image preprocessing, image analysis, and image interpretation. Details of the processes involved, equipment used, and the factors to be considered are also presented. In addition, the applications of machine vision are discussed.

This chapter discusses the operating mechanism, applications, advantages, and limitations of Brinell hardness testing, Rockwell hardness testing, Vickers hardness testing, Scleroscope hardness testing, and microhardness testing. In addition, the general precautions and selection criteria to be considered are described and details of equipment setup provided.

This chapter is a detailed account of the tensile testing procedure used for evaluating metals and alloys. The discussion covers the stress-strain behavior of metals determined by tensile testing, properties determined from testing, test machines for measuring mechanical properties, and general procedures of tensile testing. Three distinct aspects of standard test methods for tension testing of metallic materials are discussed: test piece preparation, geometry, and material condition; test setup and equipment; and test procedure.