Scratch hardness
Scratch hardness tests are used to determine the hardness of a material to scratches and abrasion. The earliest test was developed by mineralogist Friedrich Mohs in 1820 (see Mohs scale). It is based on relative scratch hardness, with talc assigned a value of 1 and diamond assigned a value of 10. Mohs's scale had two limitations: it was not linear, and most modern abrasives fall between 9 and 10.
Raymond R. Ridgway, a research engineer at the Norton Company, modified the Mohs scale by giving garnet a hardness of 10 and diamond a hardness of 15.[1] Charles E. Wooddell, working at the , extended the scale further by using resistance to abrasion, and extrapolating the scale based on seven for quartz and nine for corundum, resulting in a value of 42.4 for South American brown diamond bort.[2] Resistance to abrasion is less affected by surface variations than other methods of indentations.
There is a linear relationship between cohesive energy density (lattice energy per volume) and Wooddell wear resistance, occurring between corundum (H=9) and diamond (H=42.5).[3]
| Material | Mohs' scale | [1] | [2] | |
|---|---|---|---|---|
| talc | 1 | 1 | ||
| gypsum | 2 | 2 | ||
| calcite | 3 | 3 | ||
| fluorite | 4 | 4 | ||
| apatite | 5 | 5 | ||
| orthoclase | 6 | 6 | ||
| vitreous silica | 7 | |||
| quartz | 7 | 8 | 7 | |
| topaz | 8 | 9 | ||
| garnet | 8.92[2] | 10 | ||
| corundum | 9 | 9 | ||
| fused zirconia | 11 | |||
| fused alumina | 9.03–9.065[2] | 12 | 10 | |
| tungsten carbide | 9.09[2] | 12.0 | ||
| silicon carbide | 9.13–9.17[2] | 13 | 14.0 | |
| boron carbide | 9.32[2] | 14 | 19.7 | |
| diamond | carbonado | 9.82[2] | 15 | 36.4 |
| ballas | 9.99[2] | 42.0 | ||
| bort | 10[2] | 42.4 | ||
References[]
- ^ a b Ridgway, Raymond R; Ballard, Archibald H; Bailey, Bruce L. (1933). "Hardness Values for Electrochemical Products". Transactions of the Electrochemical Society. 63: 369. doi:10.1149/1.3493827.
- ^ a b c d e f g h i j Wooddell, Charles E. (1935). "Method of Comparing the Hardness of Electric Furnace Products and Natural Abrasives". Transactions of the Electrochemical Society. 68: 111–130. doi:10.1149/1.3493860.
- ^ Plendl, Johannes N.; Gielisse, Peter J. (1 Feb 1962). "Hardness of Nonmetallic Solids on an Atomic Basis". Physical Review. 125 (3): 828–832. Bibcode:1962PhRv..125..828P. doi:10.1103/PhysRev.125.828.
 | This material-related article is a stub. You can help Wikipedia by . |
- Hardness tests
- Materials stubs