In the beginning, sol-gel corundum was used as the solitary abrasive grit type in grinding tools (percentage of 100 %). However, its toughness led to excessive grinding forces. Today typical blends are 50, 30 and 10 % of sol-gel corundum with white corundum or mono-crystalline corundum as secondary grits [KLOC03, MARI04, p. 378, MULL01]. In 2003, sol-gel corundum was about 15-20 times more expensive than pure white corundum [KLOC03].
Furthermore, the usage of sol-gel corundum in vitrified bonds was limited by the sintering temperatures of the bond. Temperatures above 1200 °C result in aggregation of the micro-crystals, which reduces the efficiency of the abrasive grits. Therefore, low-fired bonds were developed resulting in spreading of sintered corundum grinding tools [KLOC03].
Compared to superabrasives, sol-gel corundum has much lower production costs. Therefore, it can be used in solid body grinding tools instead of thin abrasive layers. As a consequence, the sol-gel corundum tools can be reprofiled more often and are flexible for different workpiece profiles [KLOC03].
Sol-gel corundum wears by favorable micro splintering when a minimum load is exceeded (Fig. 2.9) [MULL01, ENGE02]. Especially for high material removal rates, sol-gel corundum has a higher performance than conventional abrasives, but is less expensive than CBN. Thus, the full potential of sol-gel corundum evolves only at high cutting speeds and high material removal rates. Sol-gel corundum shows a quasi stationary cutting performance even at higher grit load until the break-down of the abrasive layer. Therefore, high surface qualities are possible at shorter machining times [KLOC03].
In applications with low process loads, sol-gel corundum grinding tools have only minor advantages in performance and wear resistance against conventional abrasives [KLOC03, MULL01, p. 123]. In fact, sol-gel corundum grinding tools have to be applied at high process loads to maximize their potential [KLOC03, MULL01, p. 123]. Sol-gel corundum showed much lower radial wear and a higher maximum specific material removal rate than pure white corundum at high load or cutting speeds (e. g. vc = 63-125 m/s) [KLOC03].
In single grit scratching tests, a highly viscous oxide layer formed on the grit edge of sol-gel corundum [KLOC02]. This oxide layer presumably reduces the strain energy between the workpiece and the abrasive grit, so that friction coefficient and grit wear are decreased [KLOC02].