Abstract
Since conventional indenters used for hot hardness testers by which the measurement of indentations can be performed in the furnace heating the specimen are of diamond indenter points fixed into metallic mounts, the temperature on the region of the indentation inevitably falls mainly as the result of heat conduction during the indenting process even if the indenter point has been adequately preheated, so that correct hot hardness value of the specimen cannot be obtained at the predetermined testing temperature.
On the basis of theoretical considerations on the behavior of heat transfer, highly effective heat insulating diamond indenters to be used for the measurement of the hot hardness of the materials harder than sapphire have been produced on trial in order to obtain a closely correct hot hardness value at every testing temperature up to about 1000°C.
The results of hot hardness measurement showed that the heat insulating effect of the indenters produced on trial was closely similar to that of the solid sapphire indenter. Moreover the measurement of hot hardness of various ceramic tool materials up to 1000°C could be perfectly carried out by means of these heat insulating diamond indenters.
