Determination of modifying additives and impurities in Nb – Si-based composites using inductively coupled plasma atomic emission spectrometry (ICP AES)

Abstract

The evolutionary development of structural heat-resistant superalloys has led to creation of high-temperature niobium-silicon based natural composite materials (CM) which are promising for manufacturing of aircraft gas turbine engine blades with an operating temperature of up to 1350°C. To impart the necessary properties (heat resistance, heat resistance, creep resistance, fracture toughness, manufacturability, etc.) CM are doped with modifiers, e.g., B, Ge, Sn, Zr. When using the technology of mechanical alloying for production of niobium-silicon based composites Fe and Ni can enter the material as technical impurities. The quality of materials is the first concern in the aerospace industry. Accurate determination the matrix, alloying and impurity elements in the CM composition is necessary for quality control of the semi-products and off-the-shelf CM. We improved the method of ICP AES with microwave sample preparation for determination of the chemical composition of niobium-silicon based composite materials. The analytical lines of B, Ge, Sn, Zr, Fe, and Ni free of significant spectral overlap are used. The range of the determinable contents (wt.%) is: Nb — 40 – 80; B, Ge, Zr — 1 – 5; Sn — 1 – 2.5; Fe — 0.01 – 10; Ni — 0.01 – 5. To evaluate the metrological characteristics of the method, model solutions similar in composition to the composites analyzed, prepared from certified solutions of the ions, were used as reference samples. State standard reference samples of ferroniobium and titanium alloys similar in composition to Nb – Si based CM were used to verify the accuracy of the technique in spiked tests. The repeatability and intermediate precision indices did not exceed 2 and 4 %rel., respectively, for all the elements studied.