Many materials have complex microstructures, the chemical and structural aspects of which crucially determine performance. Thus measurements methods are required to accurately describe these micro features, and electron-probe microanalysis (BPMA) is widely used in industry, test houses and research organisations to determine the chemical composition of areas only a few microns in diameter. Unfortunately, although widely used, standardisation of the measurement method is only just beginning. ISO TC202 dealing with this topic is only just starting its work, while in CEN so far only one ENV has been drafted by TC 184 which relates to ceramic coatings. In the latter case, the important issue of light element analysis was not addressed.
In many materials, particularly steels and corrosion and wear resistant coatings light elements (low atomic number) play a major role in determining performance, but are difficult to analyse by EPMA, and special methods have to be devised. Because of the importance of the measurement method many different organisations have evolved their own "standards", but none of these are generally accepted. Increasing tightness of specifications requires highly accurate analysis, and without validation of the existing methods there can be no certainty as to the results obtained in the individual organisations.
The research to be undertaken in this proposal is focussed on the microanalysis of carbon and nitrogen. Reference materials based on Fe3C and Fe4N will be produced, and their homogeneity and stability established. The procedures to be adopted follow those recommended in the document BCR/48/93, Dec l994. In order to comply with this procedure it will also be necessary to develop an accurate measurement methodology. This is needed to optimise what are normally weak signals, and establish the validity of a linear compositional relationship between zero and that present in the compound. This will be carried out using a range of steels containing C and N in solid solution as well as a range of common carbides and nitrides. Having established the optimum measurement parameters, batches of the reference materials will be produced and certified using the optimised methods. The results of the certification will be analysed using recommended BCR statistical software packages to determine the certified values and their uncertainties. The certified reference materials (CRMs) will then be prepared for storage by IRMM.
Thus the main deliverables will be production and certification of and the optimisation of a measurement methodology.
Funding SchemeCSC - Cost-sharing contracts
S60 3AR Rotherham
11379 Los Barrios
2628 AL Delft
06730 Saint Andre