Tech 28 CeramicDurable Sealing Surfaces for Corrosive Environments
TECH 28 is a composite ceramic material which adds a dimension of toughness to the composite coating line. The initial slurry is chemically modified to enhance wear characteristics when in contact with seal material. Subsequent thermochemical processing bonds precursors into the substrate resulting in a very hard, extremely dense, and chemically inert coating.
BOND STRENGTH
TECH 28 develops a bond into the substrate through the formation of a spinel-like interface between the ceramic coating and the metal surface. During initial processing part of the thermochemical reaction causes the substrate metal's surface atoms to migrate into the ceramic coating while some of the ceramic molecules are moving into the substrate . Like that of the Tech 22 and Tech 23 coatings, TECH 28's bond strength to the substrate is in excess of 10,000 psi.
TECH 28 is an almost totally dense (>97%) ceramic coating and, like the Tech 23 coating, has no open porosity to the substrate. Modification of the inter-granular bonding mechanism substantially increases the density of the initial coating. TECH 28 processing completely seals off this open porosity, making the part impervious to most chemical attack.
HARDNESS
The particles in TECH 28 coating range in hardness from 1000 to 2850 Vickers. In sliding wear applications, the surface wears as a result of the hardest component, chromium oxide, which has a hardness of 2850 Vickers.
RESULTS
The unique combination of particle hardness, density, chemical bonding, and lack of porosity result in a coating which is both durable and chemically resistant. A slight surface profile will allow lubrication of mechanical seals. Field use in pump sleeves and on seal surfaces proves that life expectancy of parts can be measured in years instead of weeks or months.
TECHNICAL DATA
HARDNESS
Particle micro-hardness typically 1000-2850 Vickers
OXIDATION RESISTANCE
Protects steel from oxidation to 850°C(1560°F)
CORROSION RESISTANCE
+2,000 hours in brine (no damage)
COEFFICIENT OF FRICTION
0.25 - 0.29 against polymeric fibers (adjustable)
0.10 - 0.13 against metals (adjustable)
SURFACE FINISH
16 to 125 micro-inches rms (polishable)
THICKNESS
0.002" to 0.004" (0.05mm to 0.125mm)
BOND STRENGTH
In excess of 10,000 psi (69 Mpa)
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