Since hardness testing at high temperatures mostly is not available, so is it possible that room temp hardness values may be used to relate wear rate of alloys tested at elevated temperatures around 500degrees
Definitely not. Most materials loose their hardness not linearly, or get even harder at elevated temperatures. You have to be careful. Measured values can change after long time exposure to heat.
If you want to know at least some data, you can have a look at my publications, since we built a hot hardness test rig in our company.
Thanks Sgk and Harald,
Harald, actually I tested Fe-based sintered composite at 500 degree for two hours on pin on disc test rig, so what do you advice in this case because for justifying the results I need hardness as wear rate is to be related to hardness
The composite showing better wear resistance in my research at 500 degree is the one having high hardness at room temperature. The high hardness is because of grain refinement, so would it possible to quote the hardness(room temp) as reason for improved wear resistance at high temperature(500 degrees)
No. An clearly example are the high carbon steels used for making cutting tools.
No. Temperature increase cause hardness dropping and if the temperature is enough the microstructure can also change and you don't know it's wear resistance at that temperature.
Sure no, hardness is depend mainly on the grain size and any increase in the temperature will directly increase the grain size and so decrease the hardness value. So it it is better to measure the hardness after increase the temperature and use this value in your wear work.
This is likely an extrapolation of an extrapolation. Depending on what wear mechanism you are concerned with, hardness might or might not be a good predictor. If you are only going to 500 K then for many higher temperature materials this is not a large jump from room (293 K) and room temperature hardness might be an ok predictor of relative abrasive wear rate at 500 K for many Fe, or Ni, or Co, (and others) based alloys.
It depends on the phases present in your material, which in turn depend on the chemical composition and heat treatment conditions. For example, a quenched steel that has a high carbon content has a high amount of residual austenite having a relatively low hardness but promoting less wear.
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