Wear-resistant materials

Hydrodynamic principles for gas bearings are similar to those involved with Hquid lubricants except that gas compressibility usually is a significant factor (8,69). With gas employed as a lubricant at high speeds, start—stop wear is minimized by selection of wear-resistant materials for the journal and bearing. This may involve hard coatings such as tungsten carbide or chromium oxide flame plate, or soHd lubricants, eg, PTFE and M0S2. 

Included in tungsten carbide powder cutting and wear-resistant materials. 

Types of Wear. There are several distinct types of wear that can be divided into three main categories abrasive wear, sliding wear, and erosive wear. The type of wear encountered in a particular appHcation is an important factor influencing the selection of a wear-resistant material. 

The use of harder materials enhances wear resistance, but this conflicts with achieving adequate ductihty to avoid catastrophic brittle fahure, so these two effects must be balanced. Wear-resistant materials can be divided into three groups (1) abrasion-resistant steels, (2)... 

Carbides are hard and wear-resistant materials which have a high melting point, are thermally stable, and are generally chemically resistant (although their resistance to oxidation is generally poor). Their composition often varies over a wide range and, as a result, their properties may vary considerably. Some carbides, suchasB4C, SiC, TiC, andWC, are maj or industrial materials with numerous applications.bl... 

It is believed that the air velocities in a large-diameter dilute-phase system can be 50 to 100% higher than an equivalent well-designed dense-phase system. Hence, much greater wear problems are expected in the dilute-phase system, although significant advances have been made in the technology of wear-resistant materials and bends (Wypych and Arnold, 1993). Other features involved with dilute-phase transport systems include ... 

Polymers were never intended to be bearing- or wear-resistant materials and in fact are usually unsuitable for tribological purposes. Hence, the number of polymers with valuable tribological properties is limited. Table 2 shows the most important polymers used for tribological applications along with their tribological characteristics [35]. 

The LDPE production with tubular reactors (see Section 5.1) requires some sophisticated control valves [45]. The let-down valve (Fig. 4.2-6 B) controls the polymerization reaction via the pressure and temperature by a high-speed hydraulic actuator (9) together with an electronic hydraulic transducer. The position of the valve relative to the stem is determined by a high-resolution electronic positioner (7). The cone-shaped end of the valve stem (2), as well as the shrunk valve seat (3) are made from wear-resistant materials (e.g., sintered tungsten carbide) in order to tolerate the high differential pressure of around 3000 bar during the expansion of the polymer at that location. 

The screen is typically constructed of a wedge-bar with an aperture between adjacent bars, which opens up to a larger radius. This prevents sohds from blinding the screen as well as reduces conveyance torque. For abrasive materials such as coal, the screens are made of wear-resistant materials such as tungsten carbide. 

RT/Duroid M. [Rogers] FIFE, glass-reinforced wear-resistant material for seats, seals, bearings fm chemical and food processing equip., backup rings in hydraulic service, rub strips in B-IB bomber, mictowave dielec, diermal insulation, clutch face gaskets. 

Thus, in the spring of 1984, an international symposium with the theme Polymer Wear and Its Control was held, and is the basis of this book. The purpose of the symposium was to seek better understanding about wear mechanisms of polymers and to develop new wear-resistant materials. Distinguished scientists and engineers were invited from West Germany, England, Japan, and the U.S.S.R. to present plenary lectures. Thirty-one papers were presented. The conference was very much appreciated by those who attended. 

For structural design, the availability of high strength polymers and liquid crystalline polymers in recent years opens up new opportunities in competing with metals as wear resistant materials. Certainly, there are still more tribological studies needed to be done in establishing low wear polymers for each tribological system. 

Leather is the tough, wear-resistant material created from animal hides and skins by a number of processing steps ... 

Corrosion-resistant and wear-resistant materials (e.g., stainless steel and in special cases suitable plastics) have to be used for the equipment required to produce and apply waterborne paints. This applies to production vessels, storage and transportation vessels, to the feed system used for application (e.g., closed circuit tanks, pipelines, and pumps) all of which must be able to withstand chemical mechanical stress. The use of corrosion-resistant materials for the spraying equipment is also advantageous. 

Structural Hardness (SiC, TiC, TiN, Al Oj) Cutting tools, wear-resistant materials, mechanical seals, abrasives, armor, bearings... 

The fact that wear starts at the surface of the work piece suggests that only the tribologically stressed surface should be strengthened instead of making the entire component out of wear-resistant material. It should be borne in mind that the base material has to fulfill other functions such as load-bearing as well as surface stressing (i.e., the surface that has been made wear-resistant must not interfere unduly with the component). 

Tungsten carbide is a wear-resistant material used in the metalworking, mining, and construction industries for machine parts and dies that are subject to severe service conditions. It is produced by carburization of tungsten powder. The United States uses about 55001 of WC each year. 

Useful for feeder design indicates potential need for wear-resistant materials. 

In furnaces with bottom zones, such as pusher or walking beam steel reheat furnaces, each skid rail, on which the loads rest or slide, consists of a schedule 160 pipe, 6.625" (0.1683 m) OD with 0.718" (18.24 mm) wall thickness, through which cooling water is circulated. A solid skid wear bar is securely welded onto the top surface of the pipe. The skid wear bars are often small diameter bars of heat-resisting, wear-resisting material. Their small diameter allows less contact area with the load pieces, thereby minimizing heat loss from the loads. 

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