Evidence-first editorial standard
This guide separates observed facts, engineering assumptions and data that still require confirmation. It does not promise a universal service life or replace the exact product data and project specification.
Each hardness scale answers a different question, so figures from two scales cannot be compared directly
Mohs ranks which material scratches which; Vickers and Knoop measure the size of a diamond indentation; Rockwell measures indentation depth under a set load; Brinell measures the indentation of a hard ball. Conversion tables exist for steels, but they do not hold for ceramics, so a ceramic Vickers figure and a steel Brinell figure tell you only that one is harder, not by how much it will outlast the other.
Mohs is a scratch ranking, useful for one comparison only
The scale orders minerals from talc to diamond by which scratches which, with quartz at 7 and corundum — crystalline alumina — at 9. Its value for wear is the comparison between the lining and the particles: a surface softer than the particles it handles wears quickly by scratching, while a surface harder than them wears much more slowly. Because the steps are unequal, Mohs numbers should never be averaged or subtracted.
Vickers and Knoop are the usual scales for technical ceramics
A diamond pyramid is pressed into a polished surface and the size of the impression gives a hardness number, quoted with the load used, because the result changes with load on ceramics. Two Vickers figures are comparable only at the same load. Rockwell A, a depth-based scale, is common for cemented carbides and some hard coatings.
Brinell is the scale of wear steels
Abrasion-resistant steel grades are commonly named by their nominal Brinell hardness, and hardfacing deposits are often quoted in Rockwell C. Comparing such a steel with an alumina tile on hardness alone overstates the ceramic’s advantage in impact and understates it in sliding wear — the trade-off described in ceramic versus AR steel.
Hardness is necessary, never sufficient
Wear life also depends on toughness, the wear mechanism, the particle size and shape, the fixing and the geometry; a hard face that cracks or detaches wears nothing because it is gone. The article on why hardness alone does not predict wear life develops the point, and abrasion tests such as ASTM G65 rank materials closer to service than hardness does.
What to ask when a supplier quotes hardness
Ask for the scale, the load and the test standard, the grade and format tested, and the number of measurements. Then ask for the evidence that matters more: an abrasion test in a stated procedure, the toughness where impact is present, and the wear seen in a comparable duty. Hardness figures for Induscoat ranges are published only from verified data sheets.