Gordon Wrote:Hi Simon
to the Surface Engineering Forum.
Any chance of sharing your response here for the rest of us?
Hi Gordon, thanks for the welcome! As with all these things their are obviously some company sensitive issues i cannot discuss however most of this information is available to the public and i am more than happy to answer any technical questions on this subject. Our hardness systems conform to ISO 14577 parts 1, 2 and 3. If you have a look at these they describe how these instruments work and methology behind them.
The significant issue here from an application point of view is that measuring THIN hard coatings can be problematic due to the need to use relatively low loads as not to penetrate into the substrate material and give false results. No more than 10% of the total coating thickness is the rule, but in any event with these applications it is not possible to measure the HV value from the indent impression using optical systems, you simply cannot see the indent with the limitations on magnification, any other attempts to measure is just a guesstimate. Here we can use the Fischer instrument to relatively measure HV by indentation hardness (HIt)conversion (F/A - n/mm2) and therefore achieve a respectable result with ease. An attempt is made in a lot of areas to section a hard coated component, mount the sample and indent the cross section, however the higher loads used will impact on the edges of the coating and the substrate so in effect you have same problem limitation. If surfaces are reasonably flat, we can measure directly onto the surface of a hard coated component without the need to section, providing a further advantage at the finished component inspection stage. Being able to control the depth is also a big benefit so you can limit the indentation penetration as long as know the total coating thickness you will not interfere with the substrate.
Maybe too much sales there...sorry! Anyway, there is much more to say so if anyone has any questions or input on the subject of hardness and thickness measurments of coatings in this area i would be more than happy to discuss.
Many Thanks
Simon