Seznam abstraktů 2023: SEKCE D - MODERNÍ TRENDY V POVRCHOVÉM INŽENÝRSTVÍ

High Pressure Cold spray (CS) belongs to the family of thermal spraying technologies. The technology consists in accelerating microscopic particles to supersonic speed and depositing them on a substrate, where kinetic energy is converted into deformation and thermal energy at the moment of impact. Compared to conventional processes, CS offers particular advantages, as the spray material is neither melted on nor melted off during the process. This fact minimizes the thermal influence on the layer and substrate. A typical CS beam is narrow and well-defined. Because CS can be used for the fabrication of near-net-shape articles this technology has been recently applied as an additive manufacturing process. With cold spray is possible to produce individual components. It is also possible to repair damaged components. In comparison with fusion based high temperature additive manufacturing processes, CSAM (cold spray additive manufacturing) has shown to retain the original properties of the feedstock, to produce oxide-free deposits, and to not influence underlying substrate materials during manufacturing process. This lecture aims to provide a brief introduction to cold spray technology and CSAM.

The use of anti-corrosion paint coatings on steel pipes is a common practice for their protection against corrosion. However, such coatings may have an impact on the results of the thermographic inspection, which can be used, for example, for their corrosion damage identification. In this study, we investigated the influence of anti-corrosion paint on the thermographic inspection of curved steel tube parts. Long pulse thermography inspection was conducted on painted and unpainted samples, and the results were compared. It was found that the used painting reduced the absorbed energy, however, the contrast of the found defect indications was better on painted samples. The experiments indicated that any inhomogeneity of an inspected surface due to, for example, the painting process, the presence of old painting layers, or the presence of surface corrosion, can cause irregular surface absorption patterns. It can result in signals from this unevenness that can reduce the contrast of the indications of defects. These findings can have significant implications for the use of thermography as a non-destructive testing technique for curved steel tube parts, for example, steel pipes, especially those in operation with correction paint or corrosion layers.

Manufacturers like Airbus have strict specifications concerning the process sequence of fuselage shell forming. Coating may only take place after forming because conventional processes induce large deformation which could cause coating failure. A novel incremental bending process known as Deharde Polygon Forming® (DPF®), has the potential to challenge existing process sequence restrictions due to lower deformations. Thus, it is to be investigated if precoated sheets can be formed by DPF® with regard to the coating properties. Correspondingly, in the scope of this work, starting from the initial state of coated EN AW 2024 - T351, the changes of the Seevenax-313-81 coating were analyzed. Therefore, three different strain states were induced by Marciniak tests and scaled fuselage shells were produced by DPF® from which specimen were obtained. Afterwards, the evolution of coating properties such as hardness, Young's modulus, wear and friction coefficient were investigated by scratch and indentation tests with a Triboindenter TI 950. In parallel, the formed specimens were analyzed for coating failure by using integrated optics. It was found, that the samples of pre-stretched specimens by Marciniak tests and scaled DPF® do not undergo significant changes in their coating properties. However, the former was found to have cracks in the coating. In contrast, for scaled DPF® fuselage shells, where compressive stresses are induced by contact with the tool or spring steel package, no failure were detected in the surface of the coating. The results indicate potential for flexibilization of the process chain regarding forming and coating.

The aim of the present study was to investigate the effect of the concentration of precursors in the reaction mixture on the microstructure and electrochemical corrosion properties of MgAl-LDH coatings deposited on magnesium alloy AZ31. The concentrations of precursors Mg(NO3)2 and Al(NO3)3 were set to 0.1, 0.05, and 0.02 M and 0.1, 0.05, and 0.02 M, respectively. The deposition time ranged from 12 to 48 hours. The microstructure of LDH coatings and their chemical composition were characterized by scanning electron microscopy with an energy dispersive spectrometer (SEM-EDS). Electrochemical corrosion properties were evaluated using potentiodynamic polarization in 0.1 M NaCl solution.

This paper investigates the properties of epoxy based coatings modified with antimicrobial metal nanoparticles and microparticles. Samples of modified epoxy coating with 1% of copper or silver microparticles or nanoparticles were prepared, applied on geopolymer samples and their tribological properties were investigated by linear reciprocating tribological test and drop test to measure change in wear resistance and hydrophobicity. Properties of coatings on geopolymer samples treated with cold, atmospheric plasma were also investigated.

Magnesium and its alloys are very promising candidates for the development of temporary, degradable implants due to their biodegradability, biocompatibility and suitable mechanical compatibility with human bone. However, Mg materials are susceptible to corrosion in a physiological environment, so it is desirable to increase their corrosion resistance. Calcium phosphate (CaP) coatings are often investigated due to their good corrosion resistance and biocompatibility with bone tissues.
In this work, the effect of different concentrations of glycerol-2-phosphate and EDTA on the preparation of CaP coating on AZ31 alloy was investigated. The reaction was carried out hydrothermally at 120 °C for 2 h. To increase the adhesion of CaP coating to the surface of the substrate, AZ31 alloy was pretreated in 2 M NaOH at 120 °C for 24 h. Surface analysis was performed using a scanning electron microscope (SEM) with an energy dispersive X-ray spectroscope (EDS) and X-ray diffraction (XRD). Potentiodynamic polarization (PDP) measurements in 0.15 M NaCl were used to evaluate the corrosion properties of the prepared CaP coatings.

Dispersion of the nanoparticles in the electroless Ni-B bath is affected by various parameters. Among those, surface chemistry of the particles and bath plating composition changes more significantly the driving force for nanoparticles deposition. Therefore, optimization of these parameters is needed to obtain best possible mechanical properties. In this paper, the hardness and deposition rate of electroless Ni-B-nanodiamond composite coating was optimised by changing the concentration of electroless bath components using response surface method (RSM). The nanodiamonds and optimized coatings were characterized using XPS, FIB-SEM, GDOES, microhardness, and nanoindentation. Molecular dynamic simulation was used to study the role of nanodiamonds on borohydride reaction during electroless deposition. The role of nanodiamonds on the improvement of scratch resistance and toughness was discussed and confirmed by SEM, EDS, and Raman spectroscopy. The behaviour of nanodiamonds changes with the applied load during scratch test and observed behaviours based on the results of the Raman spectroscopy include cracking, graphitization, and lubrication. On the other hand, combining the results of Raman spectroscopy and molecular dynamic simulation on Rockwell C indentation test pointed to volume expansion caused by nanodiamond SP3 to SP2 phase transformation as a main reason for toughness improvement. Exceptional toughness and scratch resistance of the designed coating gives Ni-B coating excellent opportunities to be used in wider range of automobile and aerospace industries.

Magnesium alloys are characterized by high corrosion rates. This undesirable phenomenon can be slowed down by corrosion inhibitors. Particularly environmentally friendly molecules are in the spotlight. A possible candidate for a green inhibitor may be humic acid isolated from lignite. In this work, the corrosion behavior of AZ31 was investigated in 0.1 M NaCl with and without humic acid at pH 9. Surface analysis was performed using a scanning electron microscope (SEM) with an energy dispersive X-ray spectroscope (EDS) and Fourier-transform infrared (FTIR) spectroscopy. Corrosion behavior was investigated using potentiodynamic polarization (PDP) measurements. The results showed that lignitic humic acid accelerates corrosion in 0.1 M NaCl at pH 9 and this effect was concentration dependent.

The weight reduction of automotive body and parts become much more crucial to decrease CO2 emissions. The use of high-strength steels has increased within the scope of vehicle weight reduction studies. The corrosion resistance must be also ensured for automotive structural components. Therefore, zinc-coated high strength steels have been developed. Liquid metal embrittlement (LME) occurs during resistance spot welding (RSW) on Zn-coated high strength steels The liquid zinc from the coating penetrates along the grain boundaries in the material, where it leads to surface cracking. In this study, LME formation was investigated on zinc coated high strength steels during RSW. The effect of different type of zinc coating on LME formation was also considered. The results show that the type of zinc coating as well as the grade of the steel have considerable affect on LME formation. The maximum LME crack length was mesuared as 309 µm on GI coated TBF 1180- TBF 1180 welded joints by RSW.

In this study, the effect of citric acid as a chelating agent on the microstructure, chemical, and phase composition of hydrothermally prepared CaP coatings on AZ31 magnesium alloy was observed. The coatings were deposited in a reaction mixture at pH 5, 7, and 9, where the concentration of the chelating agent was set at 5, 50, and 500 mM, respectively. The microstructure and chemical composition of all deposited coatings were characterized by scanning electron microscopy with an energy dispersive spectrometer (SEM-EDS). The measured data were compared with thermodynamic calculations using Hydra-Medusa chemical equilibrium software.

In this paper, the main advantages of profile GDOES analysis in evaluating the thickness of zinc coating applied using hot-dip and electroplating technology on steel sheets are assessed, including the evaluation of electroplating zinc coating with chromate and chromite passivation layer.
Zinc coating is one of the surface treatments of steel products and structures in order to protect them against corrosion attack by the surrounding aggressive environment and contributes to increasing their service life. The thickness, phase structure, and chemical composition of the Zn coating influence its protective properties. In addition to destructive and non-destructive methods, optical and electron microscopy, which require time-consuming preparation of Zn-coated steel sheet samples, are also used to evaluate Zn coating. Based on the experimental work and its results, it was found that the use of GDOES profile analysis can replace optical and electron microscopy with high accuracy.