Properties erosive wear

Figure 8.12 illustrates a solid particle impinging on a surface. It has been found that the erosive wear rate depends upon the impingement angle, a, the particle velocity, vq, and the size and density of the particle, as well as the properties of the surface material. It has also been found that there is a difference in erosive wear properties of brittle and ductile materials. The maximum erosive wear of ductile materials occurs at a = 20°, whereas the maximum erosive wear for brittle materials occurs near a = 90°. Since the impingement angle is probably lower than 90° for these type of flow situations, we might consider only brittle materials, such as ceramics for this application. Let us examine brittle erosive wear in a little more detail first. 

Each person should find the remaining parameters and physical property data for this material required to solve the three models [Eqs. (8.14), (8.19), and (8.20)] for the erosive wear of a coal slurry that is, each person will have three calculations to do and three erosion rates as a result. Assume that the test temperamre is 343°C, the slurry velocity is 100 m/s, and the angle of attack is 50°. 

Studies of the properties of polyurethanes, both physical and physicochemical, showed only that resilience had some direct relationship to wear. A relationship of (1- resilience)1-4, where resilience is expressed as a fraction, has been shown (Hutchings, 1987). No other relationship has been found for other properties for erosive wear between 30° and 90° (Hutchings, 1987). External factors that affect the erosive wear of the elastomers include ... 

Coatings - for a variety of applications requiring specific properties including wear resistance, corrosion resistance, high-temperature protection, erosion protection and combinations thereof. 

Higuera, V., Belzunce, F. J. Ferna ndez Rico, E. (1997). Erosion Wear and Mechanical Properties of Plasma-Sprayed Nickel- and Iron-Based Coatings Subjected to Service Conditions in Boilers. Tribological International, VoL 30, No. 9, p>p. 641-649, ISSN 0301679X... 

The influence of an oxidizing atmosphere (air) on the hot erosion wear properties of the QllOO coating and 25Cr-35Ni-Fe was also studied. The experimental conditions for the work were identical to that reported in Table 25.4, except that the test time duration was 15 min. 

Regarding future work, CJuantiamis investigating the hot erosion-corrosion properties of other furnace alloys such as 300 series stainless steels. Inconel and Incoloy alloys. Further research will also be conducted on the synergistic relationship between hot erosion wear and corrosion. This work will include... 

Smeltzer W W, Narita T and Przybylski K, High temperature sulfidation properties of iron-chromium-base alloys , in Proc. Corrosion-Erosion, Wear of Materials in Emerging Fossil Energy Systems , Ed. By Levy AV, NACE, Houston, 1982, pp 860-872. 

The abrasion resistance of cobalt-base alloys generally depends on the hardness of the carbide phases and/or the metal matrix. For the complex mechanisms of soHd-particle and slurry erosion, however, generalizations cannot be made, although for the soHd-particle erosion, ductihty may be a factor. For hquid-droplet or cavitation erosion the performance of a material is largely dependent on abiUty to absorb the shock (stress) waves without microscopic fracture occurring. In cobalt-base wear alloys, it has been found that carbide volume fraction, hence, bulk hardness, has Httie effect on resistance to Hquid-droplet and cavitation erosion (32). Much more important are the properties of the matrix. 

FIG. 20-75 Fluid-bed erosion or wear rate as a function of granule material properties. Kq is fracture toughness and H is hardness as measured hy three-point bend tests. [Ennis [Pg.1888]

Applications Plasma spraying is used to apply coatings for protection against wear and corrosion, to prevent erosion or cavitations, and to provide electrical insulation or conductivity. It can also be employed to produce bearing surfaces, abrasive properties or resistance to wetting by molten metals. The coatings can also be applied to facilitate the joining of different materials. 

The surface of a material exposed to the environment experiences wear, corrosion, radiation, electrical, or magnetic fields and other phenomena. It must have the properties needed to withstand the environment or to provide certain desirable properties, such as reflectivity, semiconductivity, high thermal conductivity, or erosion resistance. Depositing a coating on a substrate produces a composite material and, as such, allows it to have surface property, which can be entirely different from those of the bulk material. 

The molecular weight of the polyacid affects the properties of glass polyalkenoate cements. Strength, fracture toughness, resistance to erosion and wear are all improved as the molecular weight of the polyadd is... 

The surface hardness, as measured in a standard test, is an indication of a material s ability to resist wear. This will be an important property if the equipment is being designed to handle abrasive solids, or liquids containing suspended solids which are likely to cause erosion. 

A property not listed in Table 5.14, but which is of paramount importance to this application, is wear rate. Wear rate was described briefly in Section 8.2.2, and those concepts apply here as well. As it applies to tooth enamel, abrasive wear occurs by fracture or chipping of the enamel, chemical erosion, which may arise due to acidic medications or drinks, dietary oxalate, or high oral hydrogen ion concentrations as a result of disease, physical erosion, or abrasion, which arises due to idiopathic mechanisms, dentrifices, toothbrushes, or abrasive diets. For example, the wear rate of enamel has been measured at about 10 ttm/hour due to brushing with a toothbrush and toothpaste for 86,400 strokes [7],... 

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