Laser beam machining removes, melts, or thermally modifies a material by focusing a coherent beam of monochromatic light on the workpiece. This article describes the principal lasers used in metal processing: neodymium-glass, carbon dioxide, and neodymium-doped yttrium aluminum garnet lasers. It discusses the operating parameters of concern in percussion drilling and trepanning. The process variables in surface treatment and laser cutting, as well as the operating parameters of concern in laser welding are reviewed. The article also explains the various categories of surface treatment: heat treating, cladding, surfacing, glazing, and marking.

This article focuses on a variety of laser beam machining (LBM) operations of aluminum and its alloys, namely, laser cutting, laser drilling, laser milling, laser turning, laser grooving, laser scribing, laser marking, and laser micromachining. It presents different approaches for carrying out machining operations, laser processing parameters, efficiency and accuracy of the process, and the effect of laser processing parameters on the quality of the machined surface. The article provides an overview of the various conventional (chip forming) and nonconventional machining techniques employed for aluminum-based materials. A comparison of the various aspects of LBM with other non-conventional techniques is also presented. The article also describes the features of LBM techniques employed for aluminum and its alloys for different types of machining.

Laser has found its applications in cutting, drilling, and shock-peening operations of manufacturing industry because of its accurate, safe, and rapid cutting property. This article provides an account on the fundamental principles of laser cutting (thermal), drilling, and shock-peening processes of which emphasis is placed on thermal laser cutting. It details the principal set-up parameters, such as the laser beam output, nozzle design, focusing optic position and characteristics, assist gases, surface conditions, and cutting speed. A discussion on the types of gas, supply system, purity level, and flow rates of lasing and assist gases is also provided. The article also describes the metallurgies and other key material considerations that impact laser-cutting performances and includes examples of laser cutting of nonmetal materials.

Cemented carbides belong to a class of hard, wear-resistant, refractory materials in which the hard carbide particles are bound together, or cemented, by a soft and ductile metal binder. The performance of cemented carbide as a cutting tool lies between that of tool steel and cermets. Almost 50% of the total production of cemented carbides is used for nonmetal cutting applications. Their properties also make them appropriate materials for structural components, including plungers, boring bars, powder compacting dies and punches, high-pressure dies and punches, and pulverizing hammers. This article discusses the manufacture, microstructure, composition, classifications, and physical and mechanical properties of cemented carbides, as well as their machining and nonmachining applications. It examines the relationship between the workpiece material, cutting tool and operational parameters, and provides suggestions to simplify the choice of cutting tool for a given machining application. It also examines new tool geometries, tailored substrates, and the application of thin, hard coatings to cemented carbides by chemical vapor deposition and physical vapor deposition. It discusses the tool wear mechanisms and the methods available for holding the carbide tool. The article is limited to tungsten carbide cobalt-base materials.

This article discusses the principles of operation, equipment needed, applications, and advantages and disadvantages of various fusion welding processes, namely, oxyfuel gas welding, electron beam welding, stud welding, laser beam welding, percussion welding, high-frequency welding, and thermite welding.

Impact wear can be defined as the wear of a solid surface that is due to percussion, which is a repetitive exposure to dynamic contact by another solid body. This article discusses the volume (or mass) removal of material either at or under engineering contact stress levels and outlines a rational, semi-empirical impact wear theory. It illustrates a linear wear mechanism that occurs in print heads and repetitive impacts that take place in metallic machine contacts. The article concludes with information on plotting a wear curve for an originally plane, massive carbon steel machine platen subjected to repetitive compound impact by a hard, nonwearing spherical-ended steel alloy component.

This article describes the corrosion of principal parts of mining equipment such as mine shafts, wire rope, rock bolts, and pump and piping systems. It discusses the diagnosis and prevention of various types of corrosion including uniform corrosion, pitting corrosion, crevice corrosion, erosion-corrosion, and intergranular corrosion. The article explains the corrosion in tanks, reactor vessels, cyclic loading machinery, and pressure leaching equipment.

This article discusses the generic features of impact wear on metals, ceramics, and polymers. It describes normal impact wear and compound impact wear, as well as the features of impact wear testing apparatus such as ballistic impact wear apparatus and pivotal hammer impact wear apparatus. Most mechanical components continue to be functional beyond the zero wear limit, and their usefulness is normally connected with the loss of a specific depth of material. The article reviews the zero impact wear model and some measurable impact wear models. It presents a case study illustrating the impact of wear failure on automotive engine inlet valves and seat inserts.

Impact or percussive wear is defined as the wear of a solid surface that is due to percussion, which is a repetitive exposure to dynamic contact by another body. Impact wear, however, has many analogies to the field of erosive wear. The main difference is that, in impact wear situations, the bodies tend to be large and contact in a well-defined location in a controlled way, unlike erosion where the eroding particles are small and interact randomly with the target surface. This article describes some generic features and modes of impact wear of metals, ceramics, and polymers. It discusses the processes involved in testing and modeling of impact wear, and includes two case studies.

Cutting with lasers is accomplished with carbon dioxide (CO 2 ) and neodymium: yttrium-aluminum-garnet (Nd:YAG) lasers. This article provides a description of the process variables and principles of laser cutting. It discusses the three basic types of CO 2 gas lasers, namely, slow axial flow, transverse flow, and fast axial flow and reviews the applications of Nd:YAG laser. The article describes the basic parameters in the laser-cutting process: beam quality, power, travel speed, nozzles design, and focal-point position. Several material conditions that affect the quality of the laser cut are also discussed. The article provides information on the basic laser-cutting system and its optional equipment. A general description of how well each metal group can be cut is also provided.

This article serves as a basic information source for those interested in accomplishing one-sided, no-hole attachment of metal fasteners. The stud arc-welding process is a substitute for fastening procedures such as drilling and tapping, bolting, and self-tapping screws. The article describes the operating principle of, and the tooling and equipment used for, the welding process. It contains tables that present information on the mechanical properties of aluminum, stainless steel, and low-carbon steel stud arc welded fasteners. The article details the different tests conducted to ensure the quality of stud arc-welded fasteners. It concludes with information on safety precautions to be followed in the welding process.

Stud arc welding (SW), also known as arc stud welding, is a commonly used method for joining a metal stud, or fastener, to a metal workpiece. This article serves as a basic information source for those interested in accomplishing one-sided, no-hole attachment of metal fasteners. It schematically illustrates the basic equipment used for stud arc welding and describes the operation of the welding process. The article discusses several specific applications that lend themselves to special variations of the stud arc welding technique. It concludes with information on quality control, qualification, and inspection of stud-welding.

Fracture surfaces can provide an important and indispensable record of many factors in simple or complex failures. Visual examination of fracture surfaces can reveal the type and direction of loading, with fracture-surface features often providing definitive evidence of torsion, tension, bending, and compressive loads. This article discusses tools and techniques of visual examination and characteristic features of fracture features. A brief review of ductile and brittle fracture-surface features is provided. The article also describes macroscopic features that can be used to identify fracture-initiation sites, locations of final overload, and the directions of crack propagation. In addition, the use of these features to characterize loading at the time of failure is also described.

Cemented carbides are extremely important in corrosion conditions in which high hardness, wear resistance, or abrasion resistance is required. This article describes the effect of binder composition and carbide addition on corrosion behavior of cemented carbides. It lists the examples of their uses in corrosion applications. The article provides information on the selection of cemented carbides for corrosion applications and tabulates the corrosion resistance of cemented carbides in various media. It expounds the oxidation resistance of cemented carbides and presents some tips to improve the properties of tungsten carbide cutting tools. The article also details the coating materials and coating processes of cemented carbides.

This article describes the joint preparation, fit-up and design of various types of laser beam weld joints: butt joint, lap joint, flange joint, kissing weld, and wire joint. It explains the use of consumables for laser welding and highlights the special laser welding practices of steel, aluminum, and titanium engineering alloys. Laser weld quality and quality assessment are described with summaries of imperfections and how its operations contribute to providing repeatable and reliable laser welds. Relevant laser weld quality specifications are listed.

Metal powders are used as fuels in solid propellants, fillers in various materials, such as polymers or other binder systems, and for material substitution. They are also used in food enrichment, environmental remediation market, and magnetic, electrical, and medical application areas. This article reviews some of the diverse and emerging applications of ferrous and nonferrous powders. It also discusses the functions of copier powders and the processes used frequently for copier powder coating.

Coatings and other surface modifications are used for a variety of functional, economic, and aesthetic purposes. Two major applications of thermal spray coatings are for wear resistance and corrosion resistance. This article discusses thermal (surface hardening) and thermochemical (carburizing, nitriding, and boriding) surface modifications, electrochemical treatments (electroplating, and anodizing), chemical treatments (electroless plating, phosphating, and hot dip coating), hardfacing, and thermal spray processes. It provides information on chemical and physical vapor deposition techniques such as conventional CVD, laser-assisted CVD, cathodic arc deposition, molecular beam epitaxy, ion plating, and sputtering.