Piotr Śliwiński | Silesian University of Technology (original) (raw)

Papers by Piotr Śliwiński

Metal ..., 2020

Shape memory alloys (such as Ni-Ti) are a unique class of active materials, which can recover to ... more Shape memory alloys (such as Ni-Ti) are a unique class of active materials, which can recover to their original shape after applying stimuli, such as deformation due to stress, heat or magnetic field. These alloys possess attractive characteristics such as ability to provide large recoverable strain during mechanical loading (pseudoelasticity), shape recovery upon heating (shape memory effect), and potent biocompatibility, which make alloys one of the suitable actuators for biomedical applications. In the present paper the results of microstructure, martensitic transformation behaviour and superelastic properties of Ni-Ti alloys fabricated using a EBAM technique, which applies wire as the additive material were presented. It was revealed that the microstructure of the deposit exhibited typical solidification features of columnar grains of austenite, due to epitaxial growth mechanism. Moreover, EBSD investigations revealed that the preferential grain orientation in [001] is a result of the adopted material layer deposition. TEM studies have shown presence of martensitic needles partially twinned within austenitic matrix, and a low dislocation density within austenite confirming ability of the EBAM manufactured sample to pseudoelastic deformation at room temperature.

Journal of Physics: Conference Series

One of the most popular thermal spraying technology is atmospheric plasma spraying (APS). However... more One of the most popular thermal spraying technology is atmospheric plasma spraying (APS). However, it should be noted, that numerous imperfections in the APS surface layers can be occurred. The porosity, microcracks as well as lamellar microstructure occurred. Moreover, the adhesion of the coating is limited. However, the reduction of porosity and other imperfections by remelting process can be eliminated. The laser or electron beams for remelting are the most popular technologies. Mainly, power of the beam and travelling speed influence on the thickness and the final properties of the remelted coatings. In the paper, the electron beam (EB) process for remelting of plasma spraying surface layers in relation to microstructure is presented. The Ni20%Cr + 30%Re APS coating on stainless steel substrate 316Ti grade by electron beam was remelted. The effect of remelting process on microstructure was presented. The light microscopy (LM) as well as scanning electron microscopy (SEM) and ene...

Key Engineering Materials

In this work, electron beam was used for butt brazing of austenitic stainless steel with grade 2 ... more In this work, electron beam was used for butt brazing of austenitic stainless steel with grade 2 titanium. Due to its low solidus temperature and high silver content, AWS BAg-21 filler containing Ag, Cu, Sn and Ni was selected. The joints were brazed with a defocused oscillating beam using offset. The resulting brazed joints were subjected to static tensile testing, light microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) analysis and hardness tests. By using appropriate parameters it was possible to reduce the phenomenon of diffusion of titanium atoms into the joint, which improved the properties of the obtained joints. The maximum tensile strength obtained was 244.2 MPa.

METAL 2020 Conference Proeedings, 2020

METAL 2021 Conference Proeedings, 2021

Electron beam brazing combines the advantages of carrying out the process in a vacuum with the po... more Electron beam brazing combines the advantages of carrying out the process in a vacuum with the possibilities of precisely controlled heat source. Under high-temperature vacuum conditions the oxide layer is decomposed, which improves the wetting properties of the base metal, thus resulting in better joint properties. Brazing in an inert vacuum atmosphere also allows the use of a very reactive base and filler materials. Compared to brazing in vacuum furnaces, electron beam brazing enables the heating of precisely selected areas without the need to heat the entire element, which results in less significant structural changes in the base material and less energy consumption. In this article, AISI 304 grade stainless steel sheets were brazed with the use of various copper or silver fillers. The joints were subjected to microstructure, hardness and shear strength tests. The results show the effectiveness of the electron beam method in making brazed joints on the example of stainless steel base material and the copper and silver-based fillers.

Biuletyn Instytutu Spawalnictwa

The surface hardening of steel components makes it possible to achieve high abrasive wear resista... more The surface hardening of steel components makes it possible to achieve high abrasive wear resistance without the necessity of hardening the entire cross-section of a given element. As a result, lower stress are introduced and the cost of the process can be reduced. Because of very high heating rates (of up to 10⁹ K/s) as well as the ease of dynamic deflection and focusing, the use of the electron beam to harden component surfaces enables the obtainment of surface layers characterised by required properties. This article constitutes an overview of publications concerning electron beam-based surface hardening.

Materials

The aim of this work was to develop a new coating material based on Ni20Cr alloy modified with up... more The aim of this work was to develop a new coating material based on Ni20Cr alloy modified with up to 50%wt. rhenium. The modification was carried out by the mechanical mixing of the base powder and ammonium perrhenate with the subsequent thermoreduction in an H2 atmosphere. The obtained powder consists of a nickel–chromium core surrounded by a rhenium shell. The characterization of the powders—including their microstructure, phase and chemical composition, density, flowability, particle size distribution, and specific surface area—was performed. The influence of plasma current intensity and hydrogen gas flow on in-flight particle temperature and velocity were investigated. The results indicate that there is interdiffusion between the base Ni20Cr and the rhenium shell, resulting in intermediary solid solution(s). The modified powders have a higher specific surface area and a lower flowability, but this does not prevent them from being used as feedstock in plasma spraying. In-flight m...

Biuletyn Instytutu Spawalnictwa w Gliwicach, Mar 1, 2021

Electron beam brazing is a joining technology combining the advantages of a precisely controlled ... more Electron beam brazing is a joining technology combining the advantages of a precisely controlled heat source and those of vacuum brazing process. The oxide layer decomposes in high-temperature vacuum conditions, which improves the wetting process and, consequently, leads to the obtainment of more favourable properties of the brazed joint. In comparison with brazing in vacuum furnaces, the electron beam brazing process enables the precise heating of selected areas without the necessity of heating the entire element, which, in turn, results in smaller structural changes in the brazed material and the lower consumption of energy. During tests discussed in this article, sheets made of stainless steel AISI 304 were brazed using various copper and silver filler metals. Brazed joints were subjected to microstructural tests and shear strength tests. The results revealed the high efficiency of the electron beam brazing of corrosion-resistant steel sheets using filler metals.

Welding Technology Review, 2021

Contemporary grades of structural steels are produced using a very advanced thermo-mechanical tre... more Contemporary grades of structural steels are produced using a very advanced thermo-mechanical treatment processes, so their properties strongly depend on the obtained structure. Corrosion-resistant austenitic steels have a high hot cracking tendency. Therefore, it is advantageous to use welding technologies, such as laser welding, that limit the size of the joint and its heat-affected zones and thus the deformations caused by the welding process. Laser welding is also characterized by small amount of heat transferred into the material during the process which limits the hot cracking tendency. During the tests, 8 samples made of S960QL steel and S304 steel, were prepared using a Trumpf TruDisk 3302 laser welding device. The produced samples were subjected to macro- and microscopy metallographic tests. Static tensile test and bend test were also performed as well as a hardness Vickers test under a load of 100N. Good quality joints were obtained, characterized by a small number of we...

This article presents the results of the metal deposition process using additive materials in the... more This article presents the results of the metal deposition process using additive materials in the form of filler wire and metal powder. An important problem in wire deposition using a CO2 laser was overcome by using a combination of the abovementioned methods. The deposition of a multicomponent alloy—Inconel 625—on a basic substrate such as structural steel is presented. The authors propose a new approach for stopping carbon and iron diffusion from the substrate, by using the Semi-Hybrid Deposition Method (S-HDM) developed by team members. The proposed semi-hybrid method was compared with alternative wire and powder deposition using laser beam. Differences of S-HDM and classic wire deposition and powder deposition methods are presented using metallographic analysis, within optic and electron microscopy. Significant differences in the obtained results reveal advantages of the developed method compared to traditional deposition methods. A comparison of the aforementioned methods perfo...

Journal of Materials Engineering and Performance, 2021

The electron beam additive manufacturing (EBAM) method was applied in order to fabricate rectangu... more The electron beam additive manufacturing (EBAM) method was applied in order to fabricate rectangular-shaped NiTi component. The process was performed using an electron beam welding system using wire feeder inside the vacuum chamber. NiTi wire containing 50.97 at.% Ni and showing martensitic transformation near room temperature was used. It allowed to obtain a good quality material consisting of columnar grains elongated into the built direction growing directly from the NiTi substrate, which is related to the epitaxial grain growth mechanism. As manufactured material showed martensitic and reverse transformations diffused over the temperature range from −10 to 44 °C, the applied aging at 500° C moved the transformation to higher temperatures and transformation peaks became sharper. The highest recoverable strain of about 3.5% was obtained in the as-deposited sample deformed along the deposition direction. In the case of deformation of the alloy aged at 500 °C for 2h, the formation o...