hardness abradable

[jim13]

Hallo,

I want to measure the superficial hardness. I know that I have to use the scale R15Y. According to the gordon's site ( http://www.gordonengland.co.uk/hardness/...ficial.htm ) I have to use a preliminary load of 3 Kgf and then an additional load of 12 Kgf. Could you please tell me which is the appropriate time for appplication of these loads?
Do you know if it exists a standard for these kind of measurements?

Thanks

[Gordon]

Hi jim13

to the Surface Engineering Forum.

Generally standards (N and T scales) indicate that the additional load should be applied progressively in 2-8 seconds, when pointer is steady remove load. But when condition is indeterminate due to time dependent plasticity, the standard for the material should specify the time required.

The old Metco technical bulletin "Measuring Hardness of Abradable Coatings" indicates that within 10 seconds of applying minor load and setting zero position, the major load should be applied and then removed after 15 (+1 -0) seconds.

I would check with your customer whether they have a procedure/specification for hardness testing your specific abradable coating. Also check your procedure against a calibrated test block of a similar hardness to your coatings.

A few common problems: Not applying enough abradabe coating thickness for reliable test, for softer abradables at least 0.80" (2mm) is needed. Also take care in preparing surface, the coatings are easily smeared and compacted, adversely effecting hardness reading.

Hope that helps