Hubert Matysiak

Morphology and luminescence properties of zinc oxide nanopowders doped with aluminum ions obtained by hydrothermal and vapor condensation methods

In this paper, we analyze the influence of Al doping on microstructure and light emission efficiency of ZnO nanoparticles obtained by the hydrothermal method and after vapor condensation method, where vaporization of the precursor powders was caused by high solar energy and subsequent deposition. We report an increase of lattice parameters with increasing level of doping as well as large emission enhancement, which we relate to surface passivation of recombination mechanisms and/or plasmon mechanism of photoluminescence stimulation.

Effect of pressure on synthesis of Pr-doped zirconia powders produced by microwave-driven hydrothermal reaction

A high-pressure microwave reactor was used to study the hydrothermal synthesis of zirconia powders doped with 1 mol % Pr. The synthesis was performed in the pressure range from 2 to 8 MPa corresponding to a temperature range from 215°C to 305°C. This technology permits a synthesis of nanopowders in short time not limited by thermal inertia of the vessel. Microwave heating permits to avoid contact of the reactants with heating elements, and is thus particularly well suited for synthesis of doped nanopowders in high purity conditions. A mixture of ZrO2 particles with tetragonal and monoclinic crystalline phases, about 15nm in size, was obtained. The p/T threshold of about 5-6MPa/265-280°C was necessary to obtain good quality of zirconia powder. A new method for quantitative description of grain-size distribution was applied, which is based on analysis of the fine structure of the X-ray diffraction line profiles. It permitted to follow separately the effect of synthesis conditions on the grain-size distribution of the monoclinic and tetragonal phases.

Microstructure of Haynes ® 282 ® Superalloy after Vacuum Induction Melting and Investment Casting of Thin-Walled Components

The aim of this work was to characterize the microstructure of the as-cast Haynes® 282® alloy. Observations and analyses were carried out using techniques such as X-ray diffraction (XRD), light microscopy (LM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray spectroscopy (EDS), wave length dispersive X-ray spectroscopy (WDS), auger electron spectroscopy (AES) and electron energy-loss spectrometry (EELS). The phases identified in the as-cast alloy include: γ (gamma matrix), γʹ (matrix strengthening phase), (TiMoCr)C (primary carbide), TiN (primary nitride), σ (sigma-TCP phase), (TiMo)2SC (carbosulphide) and a lamellar constituent consisting of molybdenum and chromium rich secondary carbide phase together with γ phase. Within the dendrites the γʹ appears mostly in the form of spherical, nanometric precipitates (74 nm), while coarser (113 nm) cubic γʹ precipitates are present in the interdendritic areas. Volume fraction content of the γʹ precipitates in the dendrites and interdendritic areas are 9.6% and 8.5%, respectively. Primary nitrides metallic nitrides (MN), are homogeneously dispersed in the as-cast microstructure, while primary carbides metallic carbides (MC), preferentially precipitate in interdendritic areas. Such preference is also observed in the case of globular σ phase. Lamellar constituents characterized as secondary carbides/γ phases were together with (TiMo)2SC phase always observed adjacent to σ phase precipitates. Crystallographic relations were established in-between the MC, σ, secondary carbides and γ/γʹ matrix.

Rapid prototyping in manufacturing of core models of aircraft engine blades

Purpose – The purpose of this paper is to present the advantages of computer-aided design/rapid prototyping (CAD/RP) usage in designing and manufacturing of the core models used for precise casting with direct and single solidification of aircraft engine turbine blade cores. Design/methodology/approach – The process of modelling three-dimensional CAD geometry of research blade in relation to the model of the core was presented with different wax types used in the RP technique. Findings – The geometry of the blade model has been designed in a way which allows making a silicon mould on the basis of a base prototype in the process of rapid tooling (RP/RT). Filing by different wax types was investigated in mean of the impact on filling accuracy of the mould cavity. Originality/value – The resulting models were used to make ceramic moulds and carry further work on the development of casting technology in the process of directional solidification and single crystal solidification of core blades of aircraft engines.

Characterization of Single-Crystal Dendrite Structure and Porosity in Nickel-Based Superalloys Using X-Ray Micro-Computed Tomography

X-ray micro-computed tomography system has been used for visualization in two- (2-D) and three dimensions (3-D) of the dendrite structure and pores in single-crystals fabricated by Bridgman investment casting technique. The system described in the paper reconstructs 3-D geometry from a set of 2-D images obtained by multiple slicing of an X-ray radiography image. The results obtained in this study demonstrate the effect of withdrawal rate on the primary dendrite arm spacing and porosity in single-crystal made of CMSX-4 alloy.

Influence of grain boundaries misorientation angle on intergranular corrosion in 2024-T3 aluminium

The special attention has been paid to the influence of misorientation angle of a random grain boundary (GB) on susceptibility to intergranular attack. The detailed observations of the microstructure of the intergranular corrosion (IGC) in 2024-T3 aluminium alloy (AA2024-T3) subjected to galvanic corrosion tests in two different solutions containing chloride ions (0.1 M and 0.5 M NaCl) were carried out using Scanning Electron Microscopy (SEM). The Electron Backscattered Diffraction (EBSD) technique was used to determine the grain boundary character distribution (GBCD) in the initial sample and a GBCD of corroded grain boundaries on a sample subjected to the corrosion test. The results are discussed in terms of the influence of the misorientation angle on the susceptibility of the grain boundaries to corrosion.

Structure and Properties of Nickel Aluminide Layers on INCONEL 100

The paper presents the results of investigations into the structure and properties of Ni-Al diffusion layers produced on INCONEL 100 by Chemical Vapour Deposition (CVD). The process was carried out in aluminium chloride (AlCl3) mixed with hydrogen atmosphere. The as-deposited layers were subjected to thermal treatment in vacuum to optimize their adhesion, hardness and temperature-resistance. Microstructural characterization of the coatings was carried out by scanning electron microscopy (SEM) The chemical composition was measured via EDS and the phase content was investigated by X-ray diffraction XRD. The resistance to high temperature of the coatings at atmospheric pressure was tested by applying 24-hours cycles at 950 °C. Scratch-tests provided data on the microhardness and adhesion of the coatings. The results indicate that the layers produced on the INCONEL 100 exhibit a very good adhesion combined with exceptional corrosion resistance at high temperatures.

Organic Viscosity Modifiers for Controlling Rheology of Ceramic Slurries Used in the Investment Casting

The paper presents results of the study on the rheology modifiers of ceramic slurries used in the investment casting. The ceramic slurries used in the study were based on aluminum oxide powder in silica sol binder. Following modifiers were used as thickening agents: mpj, locust bean and xanthan gums. The influence of the substances on the slurry viscosity were tested with a silica sol binder before application to the ceramic slurries. The viscosity measurements were carried out with the use of ARES and Brookfield rheometres. The results obtained demonstrate the potential of employing the investigated substances as rheology modifiers for ceramic slurries used in the investment casting.

Fatigue strength of butt joints welded from duplex steel

Welding tests were conducted using the flux-cored arc welding method on a plate made from duplex steel, grade UNS S31803, thickness of 9.5 mm with the increased 10 mm root gap. An analysis of fatigue strength was carried out, using the finite element method, on butt joints which underwent axial tension. Experimental research of fatigue strength was conducted. The influence of welding, with various root gaps, on fatigue strength was determined. A fractographic analysis of selected samples, after fatigue strength examinations, was executed. It was proven that the increase of the root gap has an influence on a decrease in fatigue resistance; however, it fulfils the requirements prescribed by Det Norske Veritas rules.

Hybrid method for rapid prototyping of core models of aircraft engine blades

The paper presents the possibility of using CAD/RP for the design and manufacture of the core models used for precise casting of core aircraft engine turbine blades, with directional crystallization process and single crystallization. The process of modelling 3D CAD geometry of research blade in relation to the model of the core was presented. The sample design, blade base model, was made by one of the incremental method of rapid prototyping Jetting System. The geometry of the blade model has been designed in a way, which allows making a silicon form on the basis of a base prototype in the process of rapid prototyping tools (Rapid Tooling). The form allows the attachment of the blade core in a place designed specifically for this purpose. The silicon form has enabled the production of wax models with the inner core. This task was achieved by proper shaping of forms with the plane of its division. The resulting models were used to make ceramic moulds and carry further work on the development of casting technology in the process of directional crystallization and single crystallization of core blades of aircraft engines.