When adequate standard samples are unable to be obtained in the analysis of high alloy steels, or when there are not enough amounts of sample, the electrolytic iron dilution method will be useful. This technique have been developed.
This method was further applied to nickel-base superalloys and these samples could be analysed by using iron and steel standard samples.
High speed steels, stainless steels, heat resisting superalloys, Ni-Co-Cr-Mo steel, Ni-Mo steel and nickel-base superalloys were analysed.
Dilution rates were examined from (1:3) to (1:100) using high speed steel (JSS 609) and nickel-base superalloy. By usual emission spectral analysis some elements (Ni, Cr, Mo and Co) showed good correlation between dilution rates and analytical values but certain elements (Mo, V, Nb and W) gave low analytical values at higher dilution rates. On the other hand, X-ray fluorescence analysis showed good results.
In order to investigate the cause of this phenomenon, the effect of interference lines during emission spectroscopy was examined using binary iron alloy standard samples. Consequently, in the case of standard samples containing small amounts of elements in question, the analytical lines are considerably affected by the interference lines in comparison with the samples diluted with iron.
Then, the method of treating data was decided as follows. Calibration curves are made using the values corrected for the effect of interference lines instead of the standard values and the analytical values are also corrected for the effect of other elements. By this procedure, the electrolytic iron dilution method may be applied to any samples, but titanium cannot be determined.
Nickel-base superalloy was remelted following the usual method and carbon, aluminum, niobium, zirconium and titanium were analysed using nickel-base standard samples.