Problem in hardness measurement 1

[replica]

Hi all,

We had done the hardness measurements on the carbon steel and found that the hardness is between 400 Hv and 500Hv which was very high. We anticipated that the high hardness was due to the incomplete removal of oxide surface layer on the material. We were not allowed to use grinder for surface preparation but had to use file. Grinder was no allowed due to safety reasons...as it produce spark. We used krautkramer MIC 10 hardness tester with UCI technique with 50N or 5kgf load. However with the same surface finish we did the measurement using uquotip 550 with leeb method and the value is 130 to 200 Hv......I was puzzled with the results and not sure which one is correct..Did eqoutip 550 give deeper panetration that the true hardness was obtained? .Any comment is highly appreciated ....Anyone had experience on this...

 

[metengr]

Replica
Your assumption was correct because of the indenter size comparison. Incomelete removal of surface oxide will effect MIC hardness results.

 

[SectionIX]

Agreed with Metengr; I've seen this before Proper removal of the oxide will render believable, repeatable results.

 

[replica]

metengr, SectionIX

Thank you very much for your comments. We had decided to redo the test after complete removal of the oxide surface. We also will try to compare the hardness result by using krautkramer MIC 10 ( UCI principle) and Equotip 550 Leeb(using bouncing ball)scale HLD and see if they give similar results. I will update the result.

 

[replica]

Hi all,

We performed the analysis after the layer had completely remove by proper filing and sand paper and found the the hardness had been reduced to 150 to 180 HV. We compared both method and the values are almost similar.

Thank you very much for the postings.

 

[Guest102023]

I want to add that surface preparation must be done using progressively finer grits, so that you don't produce a work hardened surface. I believe the MIC-10 requires 240 grit but I usually take it to 320 since that only requires another 60 seconds.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[replica]

brimstoner...Thank you for the info