I have substrate of law carbon steel (AISI 1018 ) with thickness of 10 mm, only one face of the substrate is coated by HVOF method (high velocity Oxy fuel), the coating type is Tungsten Carbide Nickel chromium (WC-Ni-Cr) , the coating thickness is about 250 -300 micrometer.
Is there any easy way to calculate or to measure the density of such this coating, because I am doing ASTM G65 test ( Dry wheel test)?.and the required density in the G65 standard formal it should be the coated density NOT as the powder density.
I tried different ways , but in each time I got different result, also I tried ASTM B 311-13 test.
Thank you
Have you measured the mass and volume of the low carbon steel plate (10 mm thickness) before Coating?
If so, after coating, you can measure the final mass (precision balance) and final volume (using liquid displacement or Archimedes principle), the increase in mass to the increase in volume would give you the density of the coating.
The only accurate way is to measure the weight of the steel plate before coating, then to accurately weigh it again after coating, using the area coated and the average thickness you can calculate the density of the coating.
Another less accurate method would be to do cross sections of the coating and try and evaluate the porosity using an SEM. A lot of preparation for this and a lot of SEM time. The preparation would require careful grinding and polishing then etching. You would need very good edge retention for this to work.
We measure the weight of the steel plate before coating, then to accurately weigh it again after coating, using the area coated and the average thickness you can calculate the density of the coating.
Many Thanks to all for replay to my question,
Unfortunately I forgot to measure the weigh of the steel before the coating process,
I am trying now to split small layer of the coating so I can get the mass and then the volume of small segment ,is this work??
Professor William, regarding to the porosity method it will be difficult to etching the coating, I tried that but does not work
If you use a diamond saw and only have a thin layer of steel, you should be able to dissolve the steel layer with an appropriate acid, giving you a free segment of coating. You might try electrolytic dissolution of the steel. This may be trial and error, to find what does not attack your coating material.
Dear Tarek,
Thermal spray coating possess different types of porosity which includes open porosity, closed porosity, interlamelar porosity etc. Water immersion method would tell you the content of open porosity and closed porosity and hence the density. However, coating detachment is a problem. I would go by depositing the coating on aluminium substrate and subsequently thinning it mechanically. Diamond cutting followed by mechanically thinning would also work in the case of steel substrate. However, aluminium is quite easier to thin down than any other material.
Regards,
Subhasisa
Thanks Nath, that is right , but it is so hard to cut the coating at exact thickness from the substrate even by using Diamond slow saw (I tried that ), I think it is beter if you measure the substrate weigh before and after coating, then get the density!
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