Hardness testing - Preferred Method

[jeffatmines]

Equotip (assuming proper calibration and trained tester) vs Brinell hammer: Any ideas on which is more accurate for testing the hardness? Thanks in advance.

Jeff Parham
Mechanical Engineer
Mining Trucks

 

[arunmrao]

What hardness range and what material. Poldi test is more subjective than equotip. I vote for equotip. ( However, the results from these must be used wwith abundant caution.)

 

[redpicker]

What are you trying to get the hardness of? A small part or a 2 ton piece of equipment? What hardness are you expecting?

Both methods are portable methods that I like to think of as estimating the hardness. How close the estimate is to the actual value can be very operator dependent with either method.

rp

 

[Guest102023]

It all depends. Hardness is a more complicated test than most folks realize, both in theory and in practice. It is frequently done incorrectly. You need to start by describing what it is you are testing.

With few exceptions I would not endorse hardness testing by a person who does not know the metallurgical implications of the test, the possible sources of error, and the limitations of each method/tester.

I probably haven't helped you much here ...

 

[jeffatmines]

We're looking for 240-290. It's a 1.25 ton part for our trucks. Cast then part of it machined; the machined portion is where we're testing. We're mostly checking supplier quality.

Jeff Parham
Mechanical Engineer
Mining Trucks

 

[jeffatmines]

The guys doing the testing itself have all been certified and whatnot.

Jeff Parham
Mechanical Engineer
Mining Trucks

 

[arunmrao]

Have you checked the test bars used in Poldi test. The correction factor ranges from 0.85 -1.10. My experience is that those test bars with a factor of 0.95-1.05 give better results. Also the manufacturer of these test bars is a factor.

 

[SRPJohn]

For a thick cast part, I would recommend the Equotip 3 with the G indenter (5mm tungsten carbide ball). Good luck.

 

[Flesh]

For my iron castings I've used the brinell hammer method and have always obtained results more true to a laboratory bench test method. Just be mindfull of the fact that the lower range of your hardness will require a good heavy 'hit' with the hammer (the softer castings tend to me more trouble). The nice thing I like about this method is that I don't need a machined surface. A good surface grind will suffice.

 

[jbeckhou]

My past experience, using both testers, I have found that the Equotip is far less accurate than the Brinell tester. If your equipment is governed by standard, I would recommend seeing if the Equotip type tester is even allowed. API doesn't allow the use of Equotip type equipment. Not sure about any other standards.

Petrotrim Services

 

[stanweld]

In our studies and a study by Aramco, the hardness obtained from Equotip was consistently lower than that acheived with Hammer(Pin) Brinnel, bench Brinnel, and MIC10/MIC20 methods; in many tests by 20 to 30 points. Hardness range that we tested was from 145 BHN to 225 BHN with polished surfaces from 120 grit to 320 grit.