Seznam abstraktů 2025: SEKCE D - POVRCHOVÉ INŽENÝRSTVÍ

Cold Spray technology represents an innovative method for surface repairs and restoration, which finds wide application across various industrial sectors. This article focuses on the applications of this technology in the repair of aircraft landing gear components and pressure vessels. Additionally, the paper addresses the repair of the turbine split line in a nuclear power plant using a mobile cold spray device.
In the repair of the landing gear component, the technology was utilized to replenish material at the site of corrosion damage. The replenished material was an aluminium alloy AM7075. The repair of the pressure vessel was conducted using AISI 316L material.
The mobile cold spray device was deployed for the repair of the turbine split line in a nuclear power plant, enabling rapid and efficient surface restoration using a nickel-based material without the need to dismantle large components. This approach not only reduced downtime but also lowered repair costs and increased overall maintenance efficiency.

Glow discharge emission spectroscopy (GDOES) is a well-established method for bulk elemental analysis and quantitative concentration-depth profiling of metals, alloys, surface-modified materials and various coating-substrate systems. A self-consistent calibration/quantification formalism exists in GDOES, providing an excellent accuracy and making possible multi-element, multi-matrix analyses based on dedicated, application-specific calibrations. The thereby used calibration model of GDOES [1] reflects well the fundamental glow discharge physics, enabling thus also analyses of materials for which no matrix-matched reference materials are available, such as high-entropy alloys, uncommon element combinations, and also conductive compounds such as some nitrides, oxides and carbides. Especially useful is GDOES for depth-resolved analysis of light elements, for which no other common methods are available or for which such methods do not work well. Examples will be given about quantitative surface- and depth profile analysis by GDOES of hydrogen [2], boron [3], oxygen and nitrogen.

[1] Z. Weiss, Calibration methods in glow discharge optical emission spectroscopy: a tutorial review, Journal of Analytical Atomic Spectrometry 30 (2015), 1038 - 1049

[2] Z. Weiss, Analysis of hydrogen in inorganic materials and coatings: a critical review, Hydrogen 2 (2021), 225 - 245

[3] Z. Weiss, P. Ashcheulov, N. Lambert, A. Taylor, J. Lorincik, K.-D. Sung, M. Davydova, V. Mortet, Analysis of boron- and phosphorus-doped diamond layers by glow discharge optical emission spectroscopy in argon and neon, Vacuum 210 (2023), 111890

The unique combination of properties of surface as well as core of steel can be achieved by the electron beam hardening. However, in order to achieve desired results, it is first necessary to obtain a surface of sufficient hardness (i.e. to increase the hardness of the surface layer using surface hardening techniques). Due to the high power of electron beam welding machines and properties of the electron beam itself, the above-named technology makes it possible to harden workpieces within a wide range of thicknesses up to about 2 mm. However, it should be noted that for such low depth of modified materials wider range of mechanical tests such as impact test or hardness maps are difficult for conducted. The analysis of the process is limited. Thus, the numerical simulation or physical simulation allow to analysis many different aspects of surface hardening. In the paper the results of electron beam hardening as well as physical simulation based on Gleeble system for C45 steel were compared. The different cooling systems were applied such as: air and water. The results indicated that at the proper cooling time the results of electron beam welding as we as physical simulation can be effectively compared. The light microscopy as well as SEM were adopted and detailed microstructure were discussed. The similar microstructure after EB process as well after physical simulation were obtained. However, only for narrow range of cooling time the results are comparable.

In the design and analysis of shell and tube heat exchangers, choosing the appropriate material is essential. Materials are chosen based on several factors, such as excellent thermal conductivity, strong corrosion resistance, and robust structural integrity. Traditional materials are often utilized in manufacturing heat exchangers due to their unique characteristics that enhance the heat exchanger's overall effectiveness. Nonetheless, exploring advanced alternative materials is essential for optimizing design and boosting efficiency. This research emphasizes designing and optimizing shell and tube heat exchangers with graphene-based materials. The study seeks to utilize graphene's superior thermal conductivity, mechanical strength, and corrosion resistance to improve the performance and longevity of heat exchangers. This research investigates the use of graphene as both a coating material and a primary component in composite materials. Shell and tube heat exchanger model were designed in the ANSYS software. There were several different phases of simulation tests that were conducted; first, each part of the heat exchanger model was tested with graphene composite material where the graphene is combined along with different traditional materials, after that the next phase of the test was carried out by analysing the graphene-based heat exchanger model for thermal analysis, corrosion analysis and structural analysis, etc., The study finds that materials based on graphene offer improved thermal conductivity and mechanical strength in the construction of heat exchanger models relative to traditional materials. The combination of graphene with conventional materials broadens its applicability to various industrial applications.

Using final machining, as a finishing technology, components with specific precise dimensions are obtained. Despite the precise type of machining, the integrity of the surface is significantly affected, and the material acquires some negative surface properties that cause a decrease in corrosion resistance. Such properties are increased hardness of the surface layers (and therefore reduced toughness), roughness or tensile residual stresses. The combination of these parameters leads in many cases to susceptibility to stress corrosion cracking or other corrosion degradation phenomena. In this work, final turning was used as the machining process using a tool with a positive cutting geometry and a sharp cutting edge, while the cutting parameters - cutting speed (100 and 250 m/min) and feed (0.12, 0.2 and 0.3 mm) were combined. The depth of cut remained the same in all cases (0.8 mm). The studied and compared materials were austenitic stainless steels AISI 304 and AISI 321. After turning their surface properties such as roughness or hardness were analysed. The susceptibility to stress corrosion cracking was monitored using the ASTM G36 test, where the samples were exposed to a boiling magnesium chloride solution for up to 96 hours. The samples were observed using SEM, where the areal density of cracks was monitored, as well as the depth and length of cracks on cross-sections. As part of the influence of cutting parameters, increased values of areal density were found with an increase in feed but also with an increase in cutting speed, while the surface of austenitic steel AISI 304 was significantly affected compared to AISI 321 under the same conditions. In addition to the exposure method, an electrochemical method was also used, specifically the electrochemical potentiokinetic reactivation analysis, the double loop method (DL-EPR), where it was observed whether the final turning in any way affects the sensitivity to intergranular corrosion, or how the resulting roughness affects the measurement itself.

This study investigates the application of infrared (IR) thermography for evaluating thermal sprayed coatings, focusing on distinguishing coatings subjected to different thermal treatments and varying porosity levels. Experimental thermographic analysis demonstrated the capability of IR thermography to differentiate between coating variants. The Fourier transform method and phase analysis at low frequencies proved remarkably effective. This approach enabled the visualization of areas with differing thicknesses in the thermographic images and facilitated detailed analysis through phase-frequency plots. The results highlight the potential of IR thermography as a powerful, non-destructive tool for characterizing thermal sprayed coatings, offering insights into their structural and thermal properties. This method holds promise for quality control and optimization in industrial applications involving thermal spray processes.

This study investigated how boronizing affects the electrochemical corrosion behaviour of boronized carbon steel 1020 (0.049 wt.% C and 12.700 wt.% B) and stainless steel 304 (0.003 wt.% C and 8.940 wt.% B). Both materials were boronized using Borax powder at 900°C for eight hours, forming boride layers on their surfaces. The light optical microscope revealed distinct differences between the two steels with carbon steel 1020 developing a thick sawtooth-shaped boride layer while stainless steel 304 formed a thin more compact layer. XRD (X-ray diffraction) analysis confirmed the presence of the FeB phase in both samples. Case boronizing significantly increased the surface hardness of both steels with carbon steel 1020 showing a greater hardness than stainless steel 304 as confirmed by hardness profiling. Corrosion resistance improved in both materials after boronizing, though the effect was more pronounced in carbon steel 1020 which saw a nearly fivefold increase in corrosion resistance compared to its untreated reference sample. Despite that stainless steel 304 remained the most corrosion-resistant overall even after the slight improvement from boronizing.
In conclusion, boronized carbon steel 1020 exhibited the greatest overall improvement in mechanical properties particularly in terms of hardness and corrosion resistance making it an excellent candidate for applications requiring enhanced durability and long service life.