Evolution of dislocation density, size of subgrains and MX-type precipitates in a P91 steel during creep and during thermal ageing at 600 °C for more than 100,000 h

International audienceThere are rather few quantitative data on the microstructure of the 9–12%Cr heat resistant steels after long-term creep. This paper presents results of the quantitative measurement of the size of MX precipitates, subgrain size and dislocation density in a P91 steel that had been creep tested for 113,431 h at 600 °C. The same measurements were conducted in the same P91 steel in the as received conditions. Transmission electron microscopy investigations were conducted using thin foils and revealed a decrease in dislocation density and an increase in subgrain size after creep exposure. MX carbonitrides are very stable during thermal and creep exposure of P91 steel at 600 °C up to 113,431 h. Electron backscatter diffraction (EBSD) investigations also revealed a significant change in the substructure of the steel after creep exposure

Analytical transmission electron microscopy and electron diffraction for characterization of multiphase Ni-P-Ti surface layer on Ti-6Al-4V alloy

The microstructure, chemical and phase composition of the hard Ni-P-Ti layer formed on the Ti-6Al-4V alloy after duplex surface treatment were investigated by light microscopy, X-ray diffraction, scanning electron microscopy and analytical/high-resolution transmission electron microscopy. These investigations showed that the improved mechanical and tribological properties of the surface-treated alloy were related to the presence of a multilayered microstructure containing several phases from the Ni-Ti-P-Al system

Phase Analysis of Multilayered, Nanostructured Titanium-Base Alloys by Analytical Electron Microscopy

Microstructure, chemical and phase composition of the hard layer formed on the Ti-6Al-4V alloy after duplex surface treatment were investigated by light microscopy (LM), X-ray diffraction (XRD) and analytical scanning, transmission and scanning transmission electron microscopy (SEM, TEM, STEM), electron diffraction and focused ion beam (FIB). Advanced electron microscopy techniques used for unambiguous identification of phases present in the surface multilayer are critically discussed. The relationship between multilayer micro/ nanostructure containing several phases from the Ni-Ti-P-Al system and improved mechanical and tribological properties is established

Phase analysis of multilayered, nanostructured titanium-base alloys by analytical electron microscopy

Microstructure, chemical and phase composition of the hard layer formed on the Ti-6Al-4V alloy after duplex surface treatment were investigated by light microscopy (LM), X-ray diffraction (XRD) and analytical scanning, transmission and scanning transmission electron microscopy (SEM, TEM, STEM), electron diffraction and focused ion beam (FIB). Advanced electron microscopy techniques used for unambiguous identification of phases present in the surface multilayer are critically discussed. The relationship between multilayer micro/nanostructure containing several phases from the Ni-Ti-P-Al system and improved mechanical and tribological properties is established

Characterisation of phases in nanostructured, multilayered titanium alloys by analytical and high-resolution electron microscopy

Surface processing of a Ti–6Al–4V alloy led to a complex multilayered microstructure containing several phases of the Ni–Ti–P–Al–O system, which improves the mechanical and tribological surface properties. The microstructure, chemical and phase compositions of the hard layer formed on the surface were investigated by LM, XRD, SEM as well as analytical/high-resolution TEM, STEM, EDS, electron diffraction and FIB. Phase identification based on electron diffraction, HRTEM and EDS microanalysis revealed the presence of several binary and ternary phases in the system Ti–Ni–P, sometimes with partial substitution of Ti by Al. However some phases, mainly nanoparticles, still remain not identified satisfactorily. Electron microscopy techniques used for identification of phases present in surface multilayers and some practical limits to their routine application are reminded here

Examination of chemical elements partitioning between the

In the present study, the partition of chemical elements between γ and γ′ phases in CMSX-4 was investigated using EDS microanalysis and electron tomography (FIB-SEM and STEM-EDS) methods. The investigation has been performed for the superalloy after standard heat treatment and the ex-service CMSX-4 turbine blade after operation for 12 700 hours and 200 starts in industrial gas turbine. The results have shown that Co, Cr and Re partition to the γ matrix, Ni and W are present in both γ and γ′ phases, while Al, Ti and Ta strongly partition to the γ′ phase. The results show the abilities of new analytical electron microscopy and electron tomography methods to characterize the microstructure and chemical composition of single crystal superalloys at the nanoscale