Savo Spaić

Microstructural constituents of the Ni-based superalloy GMR 235 in the as-cast condition

Abstract The Ni-based superalloy GMR 235 was investigated in different as-cast conditions. It consisted of the γ matrix with γ ′ precipitates, and of three minor constituents: M 3 B 2 , MC and Ti(C,N). The cooling rate influenced the size and morphology of microstructural constituents, and the composition and lattice constants of M 3 B 2 and MC.

Effect of tempering on the chemical and phase composition of MxCy precipitates in low carbon chromium-molybdenum-vanadium steel

Abstract The evolution of the chemical and phase composition of carbide precipitates in X20CrMoV12.1 steel after long-term service of 56000 h (470–530 °C at up to 18 MPa) and after heat treatment (650 and 800 °C) was investigated using transmission electron microscopy and Auger electron spectroscopy. The precipitates found were mostly of M23C6 type, the S- and χ-phase and traces of M2C. In service loaded state the presence of M7C3 precipitates was also established. The evolution sequence is obviously M3C → M7C3 → M23C6.

Microstructural characterization of alloys of the quasibinary Cu–NiBe system

Abstract Alloys of the quasibinary section Cu–NiBe were experimentally investigated with differential thermal analysis, optical microscopy, electron microanalysis, transmission electron microscopy and X-ray diffraction. The construction of the quasibinary Cu–NiBe phase diagram was made based on the experimental results. The constitution of alloys of the whole section was studied along with the investigation of the microstructure and crystallographic relationship of the NiBe phase in aged alloys from the Cu-rich corner of the Cu–NiBe system.

Effect of tempering on the microstructure and hardness of ledeburitic chromium steel X155CrVMo12.1

Abstract Ledeburitic chromium steel X155CrVMo12.1 for cold-work tools was investigated in the quenched and tempered condition. Using appropriate investigative methods the evolution of the microstructure in all conditions was characterized. The change in state of a multicomponent matrix during tempering is crucial for attaining the required properties of this steel. In the material investigated, shape, size, fraction and distribution of eutectic (primary) carbides played a secondary role. The evolution of tempered martensite and precipitation of secondary hardening carbides of M23C6-type and MC-type from the supersaturated matrix during tempering led to secondary hardening and a secondary hardness peak at about 530 °C. The results show that steel X155CrVMo12.1 also exhibits performance ability at moderately elevated temperatures.