The study focuses on microstructural evolution in a WC-Co powder mixture during Selective Laser Melting (SLM) and hot isostatic pressing (HIP) processing. This powder mixture contained a 13 ± 0.6% weight fraction of Co binder and WC particles of mean size of 3.0 ± 1.9 μm. SLM of the mixture produced samples of various densities, depending on the volumetric energy density (VED) applied. High VED levels led to densities of up to 88%. The aspects affected by changes in VED included the pore density as well as the resulting types of phases and the size of WC phase particles. At high VED, the material began to develop cracks due to embrittlement. This had multiple causes: coarsening of α-phase (WC), evaporation of β-phase (Co binder), and precipitation of η-phase. At low VED levels, pores formed, typically of nonsymmetric shapes, with sizes larger than 500 μm. Subsequent HIP processing led to an increased density, up to 96% of solid material. Contributions to this increased density were provided by structure transformations, namely, coarsening of α-phase by up to 1300% when compared to the powder grain size, and formation of η-phase. The results provided a basis for steering further research to explore to a greater depth the SLM and HIP processing of selected WC-Co powder mixtures with as yet unused ranges of process parameters.
In this contribution, the preparation of metallographic sections and characterization of the microstructure of manganese Hadfield steels are discussed. The purpose of this paper is to provide information relevant to microstructural characterization of these steels. This type of steel is characterized by high resistance to abrasive wear, which is provided by surface strengthening through strain-induced martensitic transformation. Strengthening complicates the preparation of metallographic sections because the final microstructure can be influenced by the process and it can be eventually misinterpreted. Great attention must be paid to the choice of the etchant and the etching procedure. This contribution describes the entire metallographic characterization procedure, including the evaluation of grain size, micro-cleanness and presence of carbides on grain boundaries. It provides information for manufacturers and those, whose process and examine Hadfield steels with respect to their processing routes, wear resistance, non-magnetic properties and other aspects.
The aim of this work is to study the structure of Ni-doped SrTiO 3 thin films by X-ray diffraction (XRD). All samples were prepared by magnetron sputtering on Si and SiO2 substrates. The main objective of this work is to monitor the crystallization of the deposited thin layer of Ni-doped SrTiO 3. The X-ray diffraction measurements were done on the films as deposited and after annealing in vacuum up to 900°C. The x-ray analysis was used with both geometries (symmetric and asymmetric). Those measurements allow us to get information about the influence of Ni on the final structure, the size of crystallites, the micro-strains and the deformation of the lattice. In particular, here we domonstarate that Ni doping lead to the unique stabilisation of crystall growth of SrTiO3 as compared to the undoped SrTiO 3 .
The aim of this study was to evaluate changes in the corrosion resistance and microstructure of deeply cryogenic treated (DCT) cemented carbides (CC). Changes in corrosion resistance were determined by potentiodynamic testing in artificial mine water. Microstructural changes were characterized using X-ray diffraction analysis. Four sorts of WC-Co cemented carbides with different WC grain sizes and volume fractions of cobalt binder were used for the experiment. Specimens were divided into two groups. The first group of specimens was deeply cryogenic treated (DCT) at -186°C in dry liquid nitrogen vapor. The second group of specimens was tempered at 450°C. The results of the experiments show that DCT increased the amount of ε-Co in all the types of CC compared to the tempered group of specimens. This microstructural change and a change in the micro-stresses in the surfaces of the specimens contributed to increasing the corrosion resistance of CC after DCT.
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