Papers by Author: Marek Szkodo

Abstract: The work shows the results of the tests of 9Cr-1Mo steel, which was for 10 years operated in the CCR platforming unit in Group Lotos SA in Gdańsk, and then in the laboratory was sulphidised during 166 h at a temperature of 600 °C. Sulphidation was performed in a mixture of H₂-H₂S gases at the vapour pressure of sulphur 4.1·10^-14 atm, so the order of magnitude of vapour pressure was less than that of the dissociation pressure of FeS. Although sulphidising took place in conditions which preclude any iron sulphide formation, research results have demonstrated that after 166 hour exposure in reaction mixture in 9Cr-1Mo steel produces iron and chromium sulfides. Sulphide precipitates form under a layer of fine carbides, located directly on the surface of steel. Formation of scale sulphide here is most likely caused by the penetration of hydrogen sulphide through the porous layer of carbides that increases the pressure of hydrogen sulphide. Thus the vapour of sulphur in apertures and narrow passages occurs between the layer of carbides and the rest of oversaturated carbon layer top, until its pressure value is reached allowing the formation of sulphide scaling.

Abstract: Cavitation erosion performance of modified macroscopic internal structure 316L stainless steel was investigated. The samples processed by means of SLM method were subjected to cavitation erosion test. The scanning electron microscope Philips 30/ESEM was used to examine morphology of eroded surface.

Abstract: This paper presents investigation of cavitation erosion resistance of nitrided austenitic stainless steel X5CrNi18-10. The diffusion layers were produced by using different parameters of reactive atmosphere (N₂:H₂). The microstructure, chemical composition and phase identification of the modified layer were examined using scanning electron microscopy, glow-discharge optical emission spectrometer and X-ray diffractometry, respectively. Cavitation erosion resistance of produced surface layers was investigated in a rotating disc facility. As a property characterizing the cavitation erosion resistance of manufactured surface layers were proposed incubation period and mass loss after 330 min of cavitation test. It was found that cavitation erosion resistance of modified surface layers is lower than reference material (not treated X5CrNi18-10 stainless steel).

Abstract: This paper presents investigations of nitrided cases after the glow-discharge nitriding process. The nitrided cases were obtained by using a different chemical composition of gas mixture at the temperature of 450^OC. The glow-discharge nitriding process was carried out on austenitic stainless steel, grade of steel X5CrNi18-10. The chemical composition and phase identification of the nitrided cases were examined by using the glow-discharge optical emission spectrometry (GD-OES) and X-ray diffractometry (XRD)

Abstract: This paper summarizes the results of experimental studies in which the aluminum alloy AW7075-T651 was friction stir welded (FSW) using various combinations of process parameters (rotational - R and travel speed - T). Mechanical properties of the test welds were assessed by using static tensile test and Vickers hardness measurement. The temperature of the welded plates was monitored during welding by means of thermocouples placed on both sides of the joint line, 15 mm from the weld axis as well as by using thermo camera. The microstructure, chemical composition and phase identification of the welding joints were examined using optical and scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffractometry (XRD). Investigations revealed that the temperatures at the weld center can reach values close to 550 °C and raised with R/T ratio increasing. It was found that tensile strength of welded joints is not correlated with R/T ratio and averages about 60% to 80% of tensile strength of a base material AW7075-T651. XRD analysis demonstrated that there is also deformation texture in the nugget (WN) and the thermo-mechanical affected zone (TMAZ) with strong dependence on process parameters.

Abstract: This work presents investigations of cavitation properties of different austenitic microstructures formed by laser beam machining of X5CrNi18-10 and C45 steels. X5CrNi18-10 steel was alloyed with TiC and Mn powders and surface layer of C45 steel was enriched with Ni, Mn, Cr and Nb. For alloying the cw CO2 laser beam was used as a power source. Cavitation behaviour of produced layers was investigated in a rotating disc facility. The results reveal different susceptibility to plastic deformation and strain hardening degree of surface in the early stage of cavitation erosion.

Abstract: This work presents investigations of relative cavitation resistance of carbon steel (C45) at the initial stage of erosion, after melting its surface by 6 kW CO2 laser beam. The research work was carried out on the rotating disk facility. Three areas were determined on the surface of investigated sample. Each area was eroded with different intensity. The procedures were elaborated for calculation of resistance of processed surface to plastic deformation under cavitation loading and of relative intensity of cavitation using image analysis of monochromatic picture of eroded surface. The results indicate that increase of cavitation loading intensity results in decrease of relative cavitation resistance.

Abstract: This paper presents investigation of surface layers. The diffusion layers were produced by using different parameters of reactive atmosphere (N2:H2). The research of the surface layers was performed using scanning electron microscope (SEM). The results of energy dispersive X-ray (EDX) analysis and X-ray diffraction (XRD) analysis are presented. Research reveals the influence of chemical constitution of reactive atmosphere on the change of properties of nitrided layers.

Abstract: In the work phase investigations of special brass CuZn38Al2MnFe alloy are presented. The microstructure, chemical composition and phase identification of the investigated alloy were examined using scanning electron microscopy (Philips 30/ESEM), light microscopy Leica coupled with PC computer with installed MultiScan program, energy dispersive X-ray spectroscopy (EDX) and X-ray diffractometry (XRD), respectively. The investigation of volume fraction existing phases was carried out using image analysis. It was found in the test bend that presence of Fe4Mn77Si19 phase in microstructure caused an increase of brittleness of the tested alloy.

Abstract: This work presents a mathematical model describing the cavitation erosion of materials. The model of cavitation erosion is based on Weibull’s distribution. The model describes the influence of material properties and also dimensions of the eroded area and volume of the eroded material on cavitation erosion curves i.e. cumulative volume loss and volume loss rate as a function of time of cavitation loading. In addition, there is a possibility to define cavitation resistance of materials, upon the base of the adduced model.