Want to measure residual stress in electroless nickel coated over steel substrate.
Maybe you can try X ray diffraction:
http://energy.gov/sites/prod/files/2014/03/f11/merit08_routbort_13723.pdf
http://www.icdd.com/resources/axa/vol45/V45_57.pdf
http://shura.shu.ac.uk/2479/7/stress_manuscript-5.pdf
Well, the major question is certainly how thick your coating is. For some microns XRD is a good technique... if you see reflections. Sometimes the grains might be that small, that you don't see really sharp peaks. If your coating is thicker, you can also use drill hole technique. Anyway, I would be not very surprised when your measurents (e.g. by XRD) won't show that much since the major question is, why there should be stress after a chemical (electroless) coating ? Usually we are observing stress as result of lattice strain caused by intrinsic effects (mismatch of the materials along a practically non-existing grain boundary (epitaxy), or by extrinsic effects like shot peening, grinding, fast cooling etc. Then you see different lattice constants for differently oriented grains (with respect to the sample surface).
Thickness of the coating is around 15 to 18 µm. As the coated nickel is in amorphous phase sharp peaks are not observed in XRD. But by doing heat treatment formation of sharp peaks for nickel are observed. Since my substrate is steel and coating is nickel,I would like to measure the residual stress. Need suggestion for the right method for measuring the stress.
This sound already a bit different :-). As I understood you correctly you initialized a recrystallization (or at least grain growth) by heat treatment so that you now found excellent Ni peaks in your XRD pattern. The final question keeps unchanged: Why do you think you should observe strain in this layer which you can transform into stress? It is very likely that by your heat treatment you caused a total relaxation of any strain (which - in your case - never existed since there is no reason for during coating of Ni on steel by chemical (electroless) processing). Residual stress you can only generate as I wrote above: you are performing a deforming (mechanical) process which is has to be anisotropic like forging, blasting, grinding, polishing. Or you expect a epitaxial growth of Ni on steel, but i don't see any reason why this should happen. Or do you have a experimental proof? Why do you want measure residual stress? What did you measuered that you assume the reason of this experimental result might be residual stress?
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science