Tibor Berecz

Effect of High Energy Ar-Ion Milling on Surface of Quenched Low-Carbon Low-Alloyed Steel

Surface preparation for electron backscatter diffraction (EBSD) measurements requires a lot of time and experience. We chose a lath martensitic iron based alloy to demonstrate the efficiency of ion polishing techniques. The average image quality (IQ) values from the EBSD measurements were assigned to be the characteristic parameter for surface goodness. The ideal ion sputtering time and the angle of incidence were determined, and the corresponding inverse pole figure (IPF) and IQ maps were compared to the mechanical polishing treatment.

Examination of the orientation relationships between the main phases of duplex stainless steel by EBSD

Duplex stainless steels are a famous group of the stainless steels. Duplex stainless steels consist of mainly austenitic and ferritic phases, which is resulted by high content of different alloying elements and low content of carbon. These alloying elements can effect a number of precipitations at high temperatures. The most important phase of these precipitation is the σ-phase, what cause rigidity and reduced resistance aganist the corrosion. Several orientation relationships have been determined between the austenitic, ferritic and σ-phase in duplex stainless steels. In this paper we tried to verify them by EBSD (electron backscatter diffraction).

Corrosion Resistance of TIG Welded Joints of Stainless Steels

The aim of this work was to analyze the performance of joints made by TIG (Tungsten Inert Gas) welding process in austenitic and duplex stainless steels with special regards to their corrosion resistance. Three different types of stainless steel were butt welded with TIG method. Ferric-chloride test and electrochemical treatments revealed how does the TIG process affects the corrosion resistance depending upon the alloy used for welding the joint. This work focuses on the weldability of the 2304, 2404 and 304 type stainless steel heterogeneous welds.

Decomposition of the Ferritic Phase in Isothermally Aged SAF 2507 Duplex Stainless Steel

Duplex stainless steels constitute a famous group of the stainless steels. They consist of mainly ferritic and austenitic phases. The ratio between these phases is regulated by numerous alloying elements and low content of carbon. Because of this strong alloying a lot of metallurgical processes can take place at high temperature, e.g. the decomposition of ferritic phase into σ-phase and secondary austenite. In this paper the changes of amounts of these three phases are studied by automated EBSD, saturation magnetization measurement, XRD-analysis and micro-hardness test. Similar results were obtained by the different applied measurements for the change of phase ratios due to the isothermal heat treatment.

Effects of Plastic Deformation, Heat Treatment and Molybdenum and Nickel Concentration on Lath Martensitic Microstructure

Lath martensitic microstructures were produced in steels containing 0.15% of carbon and various amounts of molybdenum and nickel. The behavior of the lath martensitic microstructure was studied during cold rolling in steels with six different chemical compositions. All materials have endured 75% deformation without damage. In addition, the effects of heat treatments on microstructures and hardness were investigated as well.

Crystallographic relations during decomposition of the ferritic phase by isothermal ageing of duplex stainless steel

In highly alloyed and duplex stainless steels the range of alloying elements leads to many different phases precipitating at higher temperatures. Duplex stainless steels consist of almost equal ratios of austenite and ferrite, and between 923 and 1273 K the ferrite begins decomposing into secondary austenite (γ2) and the σ phase. Several orientation relations between the austenitic, ferritic and σ phases have been determined by other researchers. The calculation and testing of mathematical expressions for these orientations are important for a close understanding of changes in duplex steel hardness, ductility, and other qualitative measures imposed by annealing or heat ageing. The method described in this article also offers an approach for determining parent phase orientations from inherited orientations in other metallic microstructures. When the orientation relations of adjacent grains calculated from mathematical equations and those measured by electron backscatter diffraction were compared, naturally it was found that the average orientation differs less between grains that inherit matrix structure from common parents. However, it was also found that the degree of difference depended on the variants involved in the orientations. This phenomenon can be explained by features of the microstructure and decomposition of the ferritic phase: initially the microstructure contains only primary austenite (γ1) and ferrite, then after a while it contains [beside primary (γ1) austenite] increasing amounts of secondary (γ2) austenite and the σ phase, and decreasing amounts of ferrite. The presence of two variants of austenite makes it difficult to verify parent relations for secondary (γ2) austenites.

Studying of Microstructural Effects of Surface Rolling in Materials of Railway-Car Wheel Axles by EBSD and Non-Destructive Magnetic Evaluation

Surface rolling is a cold-working technology for hardening the surface of components made from steel or ductile cast iron. This process is able to increase the hardness of surfaces and to improve fatigue properties, so it is usually used on the axles (shafts) of railway-car wheels. In this paper the influence of surface strengthening technology on the microstructure of the material of railway car wheel axles is studied by Vickers microindentation hardness test, optical microscopy, scanning electron microscopy (SEM) automated EBSD (Electron Backscatter Diffraction) and non-destructive magnetic evaluation.

Investigation of the Influence of Surface Strengthening Technology on the Material of Railway Car Wheel Axles

Surface rolling is a cold-working technology for hardening the surface of components made from steel or ductile cast iron. This process is able to increase the hardness of surfaces and to improve fatigue properties, so it is usually used on axles (shafts) of railway car wheels. In this paper the influence of surface strengthening technology on the microstructure of the material of railway car wheel axles is studied by micro hardness tests, optical microscopy, scanning electron microscopy (SEM) and X-ray line profile analysis.