Reference Materials for New Grades of Nickel Superalloys and Their Application in Spectral Analysis

Abstract

The actual direction of analytical control of heat-resistant nickel superalloys (NSAs) is the development of methods of express spectral analysis for monitoring all stages of the NSA production. To ensure high accuracy of the results obtained by methods such as atomic emission spectrometry (AES) and X-ray fluorescence (XRF) analysis, it is necessary to use reference materials (RMs) with composition corresponding to the analyzed samples. No standard samples are available for many brands of modern NSAs and their development and certification are necessary. This work presents a methodical approach to development and production of standard samples of new brands of heat-resistant nickel alloys. It is shown that, in the manufacture of NSA RMs for spectral analysis, not only the presence of material with defects (shells, cracks, nonmetallic inclusions, separate zones, different content of alloying elements and impurities) is unacceptable, but also areas with high microporosity. In this case, the samples are rejected and melted, adjusting, if necessary, the smelting modes of RM blanks. The structure and homogeneity of heat-resistant nickel alloys such as VZHM and VKNA are studied and certified values are established. The possibilities of using the obtained NSA RMs for atomic emission spectral analysis with spark excitation and XRF analysis are considered. It is shown that obtaining calibration characteristics for AES is preferable with the use of RM sets with the composition as close to the analyzed samples as possible, while in the case of XRF it is possible to use combined sets of RMs of similar in composition NSA brands. Metrological characteristics of certified reference materials (State Standard Samples) of NSAs for spectral analysis developed at VIAM over the past seven years are presented.