Jan Cwajna

Characterization of reinforcement distribution in Al/(Al2O3)p composites obtained from composite powder

A composite powder Al–(Al2O3)p obtained in a rotary-vibration mill was used as a semifinished component to manufacture particle-reinforced metal matrix composites (PRMMCs) using cast and powder metallurgy technologies. For a quantitative description of the inhomogeneity of Al2O3 particle distributions in the aluminum matrix the following methods were applied: nearest neighbor distance, radial distribution function, influence zone morphology, systematic scanning and variance analysis. All the methods showed a significantly less inhomogeneous distribution of reinforced particles in the composite manufactured with the powder metallurgy method. It was also shown that systematic scanning and variance analysis method enables precise descriptions of particle clustering as well as composite microstructure anisotropy.

Characterization of carbide phase in nonledeburitic high-speed steel containing Ti and Nb

The article has intended to give a summary of the investigations of carbides in the new nonledeburitic high-speed steel (NHSS). The carbide phase and its changes during heat treatment have proved to be both qualitatively and quantitatively different from that in conventional HSS. The influence on cutting performance from the dispersed phase has been established. These factors of service properties can be effectively controlled by means of the heat treatment.

Economical non-ledeburitic tool alloys—alloying philosophy, structure and properties

Abstract Economical non-ledeburitic tool alloys are materials of significantly lower carbide particles segregation than in conventional HSSs. Owing to worked out carbon and carbide formers balance, classical eutectic carbides were replaced by primary, hard MC type carbide particles of uniform arrangement. Numerous variants of wrought and cast alloys were produced; tools made of these materials exhibited high service properties.

Analysis of Stray Grain Formation in Single Crystal CMSX-4 Superalloy

Abstract Modern single crystal (SX) turbine blades are fabricated by directional solidification using a grain selector. The grain selection process was investigated by numerical simulation and verified by the experiment. A coupled ProCAST and cellular automaton finite element (CAFE) model was used in this study. According to the latest literature data, we designed the grain selector. Simulation confirmed an optimal grain selection efficiency of the applied selector geometry. The obtained experimental results reveal the possibility of stray grain formation in SX castings with a designed selector, in contrast to the simulation results.

Application of confocal laser scanning microscopy, atomic force microscopy, and the profilometric method in quantitative fractography

The paper presents methodology and results of a quantitative description of profiles and fracture surfaces of chosen grades of sintered carbides subjected to three-point bending. Three grades of WC-Co type sintered carbides (H30, G10, B23G) with different sizes of tungsten carbide particles (from 0.5 to 8.0 μm of average diameter) were tested. Quantitative descriptions of the fracture profiles and surfaces were performed using confocal laser microscopy, atomic force microscopy, and profilometry methods. With experimental conditions of the measurements preformed, their possibilities and limitations were analyzed. An attempt towards an evaluation of the individual methods regarding their labor consumption was made.

Effect of microstructure on properties of sintered carbides

Abstract The paper presents the methodology and results of a quantitative description of sintered carbides of WC–Co type. Quantitative relationships between the sintered carbide microstructures and properties have been determined. A set of quantitative metallography parameters has been identified which constitutes structural criteria for quality evaluation and criteria of selection for sintered carbides.

Influence of Pouring Temperature on Castability and Microstructure of QE22 and RZ5 Magnesium Casting Alloys

Magnesium alloys are widely used in automotive and aerospace industries due to their great connection of low density and good mechanical properties. They are also characterized by good castability and weldability. Their weak high temperature properties and corrosion resistance, led to development of magnesium alloys containing rare earth elements. Casting is the most popular way of manufacturing magnesium elements. However, there is a lack of investigations concerning impact of different factors on fluidity of these alloys. This paper presents results of investigations on influence of pouring temperature on castability and microstructure of QE22 and RZ5 magnesium alloys. In case of QE22 alloy, the filling length of the liquid alloy increased with the increasing pouring temperature. In RZ5 no such dependence was noted. This is probably caused by oxide films in the structure of material. Grain refinement and eutectics volume fraction also didn’t present correlation with pouring temperature.

Analysis of influence of measurement conditions on repeatable results of thermal diffusivity of ceramic moulds designed for manufacturing the superalloys castings

The article presents the study results concerning development of methodology for measuring thermal diffusivity with the laser-flash method with special attention being paid to their repeatability. The first stage involved the literature review of the problem determining an influence of variable measurement parameters including presence of graphite coating, error correction methods and laser power. The main part of the study includes evaluation of the sample structure influence. A real ceramic mould of specific porosity and green compacts made after its grinding were examined. Influence of sample thickness and interval between individual laser shots were also determined. The analysis was performed by using the Netzsch LFA 427 instrument designed for direct measurement of thermal diffusivity with the laser-flash method. The material analysed included different types of ceramic moulds designed for manufacturing the elements made of nickel based superalloys. The preliminary study performed showed that the main factor that has an influence on obtaining correct and repeatable results of thermal diffusivity study is proper preparation of samples i.e. using them in a form of directly cut out from the mould, selection of data acquisition time and interval between individual shots. It is especially important in the case of measurements taken at high temperature when radiation mechanism of heat transfer is of basic significance.

Fracture Surface Development Coefficient and Sialon Ceramics’ Bending Strength

Resistance to brittle cracking is one of the most important functional properties of sialon ceramics. Evaluation of the resistance requires an analysis of decohesion processes occuring in the material. Aiming at a comprehensive description of the morphology of typically brittle fractures, a quantitative characterization was made using different methods and techniques, regarding the surface of fractures formed in a three-point bending test. By using the parameter Sdr, determined via the surface stereometry method, the fracture surface development coefficient, RS, typical for fractography, was calculated. Analysis of the research results indicates a proportional relation between parameter RS and the sialon ceramics’ bending strength.

Quantitative Description of Overlaps on Sialon Ceramics Fractures by the Multifractal Method

A quantitative description of overlaps on fractures in sialon ceramics, is presented in the paper. A conventional analysis, aiming at the determination of the percentage share of overlaps on the basis of quantitative fractography, was preceded by stereometric/fractal analyses. They enabled the selection of representative sections of samples and then, the production of transverse microsections in those places for an analysis of the fractures’ profiles using the light microscopy method and fractographic image analysis. Based on the compared results from both methods, a successful verification was made of the research methodology developed earlier for sintered carbides and proven for a chromium-molybdenum steel.