Search Results for cold

With cold work, mechanical strength (measured either by yield strength or ultimate tensile strength) increases and ductility (measured by elongation, reduction of area, or fracture toughness) normally decreases. This chapter discusses the mechanisms that produce these changes and the factors that influence them. It explains how cold working increases dislocation density and how that affects the stress-strain characteristics of steel, particularly the onset of deformation. It describes the effects of deformation on ferrite, austenite, cementite, and pearlite, and how to optimize their microstructure for various applications through controlled deformation. It also provides information on subcritical annealing, the examination and control of texture, the use of optical microscopy to monitor the effects of recrystallization, and the effect of cold working on threaded fasteners, nails, and filaments used to manufacture cords.

Cold spray is a process technology that, for the first time, enables the rapid deposition of a wide range of metals and some other materials in the solid state at temperatures far below their melting points. This chapter provides an overview of the processes involved in cold spray process technologies, namely high-pressure cold spray (HPCS) and low-pressure cold spray (LPCS), explaining differences of LPCS from HPCS. It summarizes the historical background of the cold spray process. The growing international interest in the cold spray process from the early 2000s is also reviewed.

This chapter reviews the current understanding of high-pressure cold spraying for different materials, covering widely accepted general mechanisms for particle deposition and the processes and parameters involved. It begins by reviewing the mechanisms of bonding. An overview of the optimization of the critical process parameters for improving coating qualities is then provided. This is followed by a separate section dealing with bonding between different materials and addressing influences on adhesion to the substrate as well as the cohesion between dissimilar coating constituents. The knowledge of the basic science and mechanisms finally allows for discussion on the requirements for suitable cold spray equipment and of the parameter sets needed for successful coating deposition.

The modeling and simulation activities in the field of high-pressure cold spray can be divided into two main parts: solid mechanics and fluid dynamics. This chapter focuses on these parts of modeling work in cold spray research. The discussion covers the objective, principal concepts, methods, and outcome of modeling and simulation of particle impact and of in-flight history of particles in cold spraying. The concept of integration of particle impact and fluid flow modeling to optimize cold spray deposition for a given material is also explained.

This chapter provides an overview of the state of the art in high-pressure cold spray equipment, including both spray systems and gas supply systems. The chapter describes the commercial cold spray systems developed by companies such as Cold Gas Technology (CGT) GmbH, Plasma Giken Company Ltd, Impact Innovations GmbH, and ASB Industries. Typical helium and nitrogen gas systems used in high-pressure cold spray processing are reviewed.

This chapter elucidates the indispensable role of characterization in the development of cold-sprayed coatings and illustrates some of the common processes used during coatings development. Emphasis is placed on the advanced microstructural characterization techniques that are used in high-pressure cold spray coating characterization, including residual-stress characterization. The chapter includes some preliminary screening of tool hardness and bond adhesion strength, as well as a distinction between surface and bulk characterization techniques and their importance for cold spray coatings. The techniques covered are optical microscopy, X-Ray diffraction, scanning electron microscopy, focused ion beam machining, electron probe microanalysis, transmission electron microscopy, and electron backscattered diffraction. The techniques also include electron channeling contrast imaging, X-Ray photoelectron spectroscopy, X-ray fluorescence, Auger electron spectroscopy, Raman spectroscopy, oxygen analysis, and nanoindentation.

Increasing growth of high-pressure cold spraying applications on the industrial scale have forced global powder producers to face this challenge and develop specific powders for cold spray applications. This chapter provides information on the properties, classification, characteristics, manufacturing, and procedures for packaging of powders specific to cold spray applications.

Cold spray coatings technology has the potential to provide surface enhancement for applications in sectors such as defense and aerospace, oil and gas, power generation, medical, automotive, electronics, and railways. The ability to deposit clean metallic coatings is used in applications requiring corrosion/oxidation protection, erosion/wear protection, additive manufacturing, and fabricating free forms. This chapter discusses the function, advantages, and benefits of some of these applications.

This chapter discusses the application of high-pressure cold spray to the automotive industry field, with special attention to three applications: additive manufacturing, fabrication methods, and protective coatings. Various studies on the automotive application of cold spray are reviewed. The background and purpose of each application are presented and practical cases are discussed.

High-pressure cold spray repair process has been used on a number of different applications in the defense industry. This chapter describes various applications for cold spray systems that have operating pressures greater than 2.4 MPa (350 psi) and operating temperatures greater than 500 deg C (930 deg F).

This chapter focuses on high-pressure cold spray applications pertaining to repair and refurbishment in the aerospace, oil and gas, and power-generation industries, the last specifically involving repair of gas turbine components. Advantages of cold spray coating in the repair and refurbishment of structural engineering components are also discussed.

This chapter discusses the design and operation of forging presses and hammers. It covers the most common types of presses, including hydraulic, mechanical, and screw presses, explaining how they work and comparing and contrasting their load and displacement profiles, stroke lengths, ram velocities, and energy and stiffness requirements. It also includes information on gravity- and power-drop hammers and where and how they are typically used.

This chapter discusses the process of cold forging and its effect on various materials. It describes billet preparation and lubrication procedures, cold upsetting techniques, and the use of slab analysis for estimating cold forging loads. It likewise describes extrusion processes, explaining how to estimate friction and flow stress and predict extrusion loads and energy requirements. The chapter also discusses the tooling used in cold forging, the parameters affecting tool life, and the relative advantages of warm forging.