Determination of Crystal of Structure of Superalloy Steel of F1, A2 and A2-APS Using Bragg Formula Arithmetic

BATAN material engineers have succeeded in producing a series of super alloy steels of Austenitic type (A2) and Ferritic type (F1). Several treatments have been performed using arc plasma sintering (APS) by varying the irradiation time. In this study, X-ray diffraction measurements were performed to find out the shape of the crystal structure and the lattice parameters of ferritic steel F1, A2 austenitic steel and A2-austenitic steel with APS treatments for 2 seconds of irradiation. The calculations were carried out using Bragg formula by comparing the S-arithmetic and the interplanar spacing. Obtained that: ferritic steel F1 has a crystal form of body centered cubic (BCC) with lattice parameter a = 2.87 A. Austenitic steel A2 has a face centered cubic (FCC) structure with lattice parameter a = 3.59 A. Austenitic A2 steel sintered APS for 2 sec has a face centered cubic structure (FCC) with lattice parameter a = 3.60 A. As a comparison, there were also observations of material surface microstructure by using Optical Microscope (OM) and Electron Microscope (SEM). Assuming the same conditions of casting process, both types of test materials have similar cast-structures. The ferric steel F1 exhibits a finer grain boundary when compared to the grain boundary in austenitic steel A2 which tends to be highly visible to the width of its boundaries. While austenitic steel A2 treated sintering APS for 2 seconds, showing the grains pattern structures that previously elongated changed to become slightly rounded (globular). SEM-micrographs show the precipitates on the ferritic steel F1 scattered at the grain boundaries and inside the grain, whereas in A2 autentitic steel lies at the grain boundary only. While EDX spectrums show the precipitate composition of ferritic steel F1 including C, Cr, and Fe. While in A2 austenitic steel is C, Cr, Fe, and Ni. It is possible, because of the dominance of Cr and C elements, chromium carbide (Cr23C6) is formed as precipitates at the grain boundaries.