Hardness grain size

It is applied along with traditional methods to test strength properties, hardness, to determine standardized characteristics of stamping, grain size and other structural-sensitive characteristics. 

Chalk is a soft, fine-grained, fossiliferous form of calcium carbonate that varies widely in color, hardness, and purity. Its grain size is so minute that it appears amorphous, but actually it is cryptocrystalline with a very high surface area. 

Fig. 8. Variation with percent Co binder content for cemented WC grades of (a) hardness, where the numbers represent carbide grain size in pm (b)...

In addition to chemical analysis a number of physical and mechanical properties are employed to determine cemented carbide quaUty. Standard test methods employed by the iadustry for abrasive wear resistance, apparent grain size, apparent porosity, coercive force, compressive strength, density, fracture toughness, hardness, linear thermal expansion, magnetic permeabiUty, microstmcture, Poisson s ratio, transverse mpture strength, and Young s modulus are set forth by ASTM/ANSI and the ISO. 

Hardness (qv), which determines the resistance of a material to abrasion and deformation, is affected not only by composition but also by porosity and microstmcture. Higher cobalt content and larger carbide grain size reduce hardness and abrasion resistance but iacrease the toughness of cemented carbides. The trade-off of abrasion resistance and toughness enables the cemented carbide manufacturer to tailor these materials to a wide variety of metal-cutting and nonmetal-cutting appHcations. 

The impetus for the synthesis of WC and subsequent development of cemented carbides came from the wire drawing industry where the hard metals are stUl used. The most commonly used grade is WC-6 wt % Co with medium grain size (1—2 p.m). Compositions having higher cobalt content are used in drawing tubes, rods, and bars. 

Haidness decreases with increasing porosity and increased grain size. SoHd solution impurities influence hardness, but it is often hard to separate the effect of the impurity on the hardness, from the effect of the impurity on other microstmctural effects that influence hardness such as grain size. Further information on hardness of ceramics is available (45). 

Iridium [7439-88-5] Ir, and rhodium [7440-16-6] Rh, iadividually iacrease corrosion resistance, hardness, and strength of platinum alloys. They can be used to reduce grain size (140). 

Figure 10,3. Hardness of WC-Co cermets with nanostructured and conventional grain sizes (after Gleiter 1996, reproduced from a report by Schlump and Willbrandt).

The mechanical properties of Watts deposits from normal, purified solutions depend upon the solution formulation, pH, current density and solution temperature. These parameters are deliberately varied in industrial practice in order to select at will particular values of deposit hardness, strength, ductility and internal stress. Solution pH has little effect on deposit properties over the range pH 1 0-5-0, but with further increase to pH 5 -5, hardness, strength and internal stress increase sharply and ductility falls. With the pH held at 3-0, the production of soft, ductile deposits with minimum internal stress is favoured by solution temperatures of 50-60°C and a current density of 3-8 A/dm in a solution with 25% of the nickel ions provided by nickel chloride. Such deposits have a coarse-grained structure, whereas the harder and stronger deposits produced under other conditions have a finer grain size. A comprehensive study of the relationships between plating variables and deposit properties was made by the American Electroplaters Society and the results for Watts and other solutions reported... 

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