Research On Method Of Dynamic High-temperature Hardness Testing

Hardness testing is one of the most widely applied testing technique.Mechanics, materials science and other research field have their own requirement ofthe hardness of meterials, which could’t be without the support of hardness testingtechnique. But in the high-temperature area, we are facing the problem of lackingtesting method. The long-time used static load hardness testing theory cannot beapplied to the testing condition of high-temperature. To solve this problem, dynamicload testing theory and relative technique research was carried out. It is of greatsignificance to develop the key technology indicator of high-temperature hardnesstesting. Based on the dynamic load testing theory, the limit of testing temperature isincreased, as well as the testing precision, meeting the requirement ofhigh-temperature testing technique. This paper aims to develop the instrument whichcan reflect the hardness performance of materials exactly in high temperature, that isto say the high-temperture dynamic load hardness testing system.This paper verified the influence of small sample to the testing result, resultingin the lower and unstable value by studying and testing the dynamic load hardnesstesting theory. Confirming that fixing the samples well could effectively increase thetesting accuracy. And the height error of around1mm had hardly influnce on theresult. But the testing position had significant influence. The value got higher as thetesting position got closer to the centre of sample. The testing system should use theD type impact device of Leeb hardness tester.This study have proceeded the design of overall structural and physical modelof the principled sample machine, completed the analysis of feasibility, and finishedthe design and manufacture of hardness testing system, cacuum system,3Dpositioning system, heat protection system, software control system and so on andthe combination of the whole system. The high-temperature dynamic hardnesstesting system which met the requirement was developed successfully.The hardness of500℃~900℃of45#steel, Inconel718and graphite wastested by the testing system. The hardness of45#steel reduced significantly as theincrease of temperature, and the hardness of Inconel718reduced slower. While thehardness of graphite had no obvious change. The testing results fit the materialhardness theory, verifying that this instument could reflect the change of hardness inhigh temperature well.