Surface abrasion

Abrasion Resistance. Porcelain enamel is the most scratch resistant and hardest of commercial coatings (see Hardness). This property is used to distinguish between porcelain enamel and organic enamel or painted coatings. The rate of abrasive wear in surface abrasion increases with time, and the subsurface abrasion which follows exhibits a higher, but constant rate of wear. Abrasion resistance can be evaluated by loss of gloss or weight (35). 

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. 

In the case of solid interfaces which are in the form of coarse powders, cavitation collapse can produce enough energy to cause fragmentation and activation through surface area increase. For very fine powders the partides are accelerated to high velocity by cavitational collapse and may collide to cause surface abrasion (Fig. 3.5). For some metal powders these collisions generate sufficient heat to cause particle fusion. 

Fig. 4.4.5. Scott s surface abrasiveness of plaster cast made at WjG = 0.8 according to amount of make-up water evaporating in the drying process on unit area.

Comparison of surface abrasiveness of stoneware sewage pipes measured using 28 cm3 and 5 cm3 chambers (after Niegodzisz, 1970)... 

HARDNESS. The significance of this tern) as applied to solids lias various interpretations. Commonly, it refers to the resistance of the substance to. surface abrasion, so thut of two solids, the one that will scratch the other, as diamond scratches glass. is the harder. Again, it may denote rigidity, or lack of plasticity, or even strength in some cases a combination of several such properties. The original Mohs Scale of Hardness is delineated in Table I and further described under Mineralogy. 

For particle surface abrasions, a satisfactory empirical formulation was suggested by Gwyn (1969) as... 

Complementary observations of the aftereffects of enzymatic hydrolysis on the graft copolymers show spatiotemporally controlled degradation, leading to a new method for fine surface abrasion as well as for degradation-rate regulation of polymeric materials. 

Metal compounds reach the lubricating oil by surface abrasion or the corrosive action of acidic oxidation products. The combustion fuel products with metal ions can be combined in a complex form and thus "masked" by so-called deactivators. Materials previously referred to as corrosion and rust inhibitors also function as metal ion deactivators, due to their ability to form a coating on the metal surface. 

Similar surface abrasion processes can be applied on all thermosetting plastics. Mechanical abrasion methods consist of abrasion by fine sandpaper, carborundum or alumina abrasives, metal wools, or steel shot. The following surface treatment procedure is usually recommended for most thermosetting plastics ... 

Hie disturbance by abrasive action of the orderly arrangement of atoms in a crystal may be detected by x-ray diffraction early experiments demonstrated such phenomena (3). Armstrong (4) has described a number of x-ray techniques which have been used on inorganic materials such as quartz. Surface abrasion damage was a major problem in the technology of... 

---