Solid State Phenomena Vol. 226

Abstract: In recent years, the leading scientific centres focus their research on improvement of mechanical properties of steels used for car manufacturing. These steels belong to a so-called 2^nd generation of steels showing above-the-average plasticity while maintaining high strength. Thanks to these properties, they may be used successfully in automotive, armaments or railway industries for elements absorbing energy of a collision and ensuring high rigidity of a structure owing to their resistance to breaking. These steels are called TWIP (Twinning Induced Plasticity) steels based on their hardening mechanism. In this paper, results of studies on the influence of parameters of thermo-plastic deformation on selected properties and structure of an X45MnAl20-3V austenitic steel showing the TWIP effect are presented. Moreover, an analysis of influence of the deformation on the structure of the studied steel in tensile tests has been carried out. The studied steel was manufactured by classic casting to a concast mould, obtaining ingots with dimensions of 100×100 mm, then subjected to rolling in 4 roll passes to a final thickness of 12 mm and 3 mm. The finish-rolling temperature was 950°C and the sheets were cooled in 2 media, i.e. in air and in water. It was confirmed that the studied steel belongs to the TWIP group of steels, with mechanical twinning being the prevailing process of hardening during deformation.

Abstract: T23 is modern bainitic steel designed for use in supercritical boilers. According to producer’s data weldability of this steel is good enough to avoid post-weld heat treatment. However, some of the T23 weld joints in as-welded condition have not met the minimal ductility requirement. The impact test revealed significant differences between the joints in as-welded and heat treated condition. Metallographic and fractographic examinations have been conducted in order to explain those differences. The specimens with low impact strength were characterized by brittle fracture and non-tempered martensite presence in weld metal. It was concluded that avoiding formation of disadvantageous structure in weld metal requires conducting of post weld heat treatment or applying multi-pass welding technique with annealing run.

Abstract: The paper presents tests results of mechanical properties, hardness measurements, microstructure and the content of ferrite with the use of ferrite meter (feritscope) FMP30 and quantitative metallography technique with the use of Met-Ilo program in welded joints of steel X2CrNiMoCuWN25-7-4 with the use of TIG method. On the basis of achieved results of tests it was concluded that the applied technology of welding was correct and the usefulness as well as limitations of both methods were proved in the assessment of ferrite and austenite content in welded joints from duplex steel.

Abstract: The selection of quartzites most suitable for the production of ferrosilicon is realized by way of time-consuming industrial trials or laboratorial studies of, among others, the ability of the silica contained in quartzite to form silicon carbide with a selected reducer. Under industrial conditions, the basic criterion for the evaluation of the suitability of a raw material for the production of ferrosilicon are the technical and economic indicators of the process. Under laboratorial conditions, simple and reliable research methods are searched for, which would allow to determine the usefulness of quartzite in the process of carbon silica reduction. The article discusses comparative thermogravimetric studies as well as alternative investigations of the specific heat of three selected quartzites which fulfill the chemical composition criterion, used in the mixed charge as raw materials for ferrosilicon FeSi75 smelting.

Abstract: Paper presents results of quantitative evaluation of porosity conducted on big, thin walled airfoil turbine blades made from Inconel 713C alloy. To decrease mass, blades are design and manufacture like thin walled cored castings. Manufacturing of big thin walled casting airfoil blades is extremely difficult. During exploitation casting work undergo cycle fatigue. In that cause casting should be free of casting defects, including porosity. Conducted research focused on Inconel 713C superalloy pouring temperature effect on porosity level of cored casted turbine blade. Results were compared to porosity of solid casted turbine blade. It was found that porosity of cored blades is lower than solid blade porosity. In cored blades higher porosity is located on airfoil convex side. Airfoil concave side has lower porosity.

Abstract: Characterization of top surface and microstructure of silicide coatings obtained during diffusion process of pack cementation type and laser remelting treatments was showed in this article. The basic materials were pure Mo sheet and TZM molybdenum alloy. The coatings were deposited in powder process and glazed by different types of lasers. In first step the phase’s compositions of coatings was described by XRD analysis in initial condition and after remelting process. The morphology of the coatings top surface was described as well. All types of coatings were characterized by network of cracks on top surface of the coatings. Laser treatment of the silicide top surface changed morphology of the top surface, especially their cracks network. LM and SEM analysis revealed that internal coatings morphology was very similar in all cases.

Abstract: The paper presents the results of research on surface condition of zinc coatings. Profilometric studies were performed for zinc coatings formed in industrial continuous hot-dip galvanization process and for the same coatings after two years of use. The results include the geometrical shape of 2D and 3D surfaces, distribution of vertices on the surface and roughness and waviness profiles. The parameters R_a, R_z, S_a and S_z were used to define the surface roughness. The study was conducted using FRT Microprof optical profilometer with data acquisition and analysis by MARK III software package.

Abstract: In the paper the results of tests on obtaining coatings in a ZnAl bath of eutoctoid composition on steel with various contents of silicon by use of the batch hot dip method are presented. The growth kinetics of coatings obtained in a ZnAl23 bath with the addition of 1% and 2% of Si on steel with low silicon content (0.01% Si), on Sandelin steel (0.035% Si) and on high-silicon steel (0.27% Si) have been defined. The structure of coatings on tested steels was developed. It has been established that coatings obtained on the Sandelin steel and on high-silicon steel have similar thickness and structure as compared to coatings obtained on low-silicon steel.

Abstract: The cyclic oxidation behavior of diffusion protective Al and SiAl coatings used on Ni-superalloy namely MAR-M247 at 1100°C for 38 cycles in the air under cyclic heating and cooling conditions has been investigated in the present work. Cyclic oxidation test was carried out in laboratories of Silesian University of Technology in Katowice, Poland. Cylindrical samples were casted from mentioned alloy in factory PBS Velká Bíteš, a.s., Czech Republic. The oxidation kinetics of coated and uncoated superalloys was analyzed by thermo-gravimetric technique. It was observed that all the coated and bare superalloys obey a parabolic rate law of oxidation. SEM/EDX techniques were used to analyses the oxidation products of all samples. MAR-M247 with Al coating showed good oxidation resistance due to the formation of a compact and adhesive thin Al₂O₃ scale on the surface of the coating during oxidation. SiAl coating showed equally good oxidation resistance. The oxidation progress of uncoated alloy MAR-M247 was very fast.

Abstract: The 23MnNiCrMo52 steel is used to produce coil chains for the mining industry. The chemical composition of that steel is responsible for the high strength of chains but their corrosion resistance is not sufficient. The chains are delivered as naturally black, treated with anti-corrosion oil or painted. They are not generally protected against corrosion by hot dip zinc coatings due to their specific shape and complex chemical composition of steel. In the paper the authors present the results of tests on obtaining zinc coatings on the 23MnNiCrMo52 steel. The growth kinetics of the coatings has been defined, their structure has been developed and the chemical composition of particular structural components of the coating has been established. It has been determined that the obtained coatings are continuous and uniform and their morphology depends on the chemical composition of the galvanized steel.