L. K. Varga

57191521187

Publications - 5

3D printed metal-insulator layered structure

L. K. Varga István Hatos B. Kocsis

Publication Name: Journal of Magnetism and Magnetic Materials

Publication Date: 2022-12-01

Volume: 563

Issue: Unknown

Page Range: Unknown

Description:

Additively manufactured metal–insulator layered structures are facing a contradictory demand. Laser sources with different wavelength are required to melt the two materials. In the present study we attempt to additively manufacture metal–insulator composite using a fiber laser. Three different procedures are presented. Firstly, production of a core–shell soft magnetic composite by laser-powder bed fusion technology from a unique amorphous alloy. Lastly the preparation of Fe-Si and Fe-TiN layered structure is discussed. Further improvement of Fe-TiN can be achieved by oxidation heat-treatment. Microstructure, porosity and complex permeability spectra were studied.

Open Access: Yes

DOI: 10.1016/j.jmmm.2022.169994

Development of High-Entropy Alloy Coating by Additive Technology

L. K. Varga B. Kocsis Gábor Gulyás

Publication Name: Frontiers in Materials

Publication Date: 2022-01-18

Volume: 8

Issue: Unknown

Page Range: Unknown

Description:

In this research study, various additively fabricated coatings and bulk 3D-printed parts were prepared, using the mechanical and corrosion-resistant properties of CrMnFeCoNi (Cantor alloy) and AlCrMnFeNi high-entropy alloys (HEAs). The coatings were applied to an EN 1.0038 carbon steel substrate using direct metal laser sintering. We attempted to optimize the 3D printing parameters of HEA alloys. The effect of volumetric energy density (VED) on the microstructure was investigated by scanning electron microscopy. We also examined the change of relative concentration of alloys in the direction of 3D printing (z-axis) as well as the volumetric failures (cracks and gaps). Standard salt spray tests were performed to test the corrosion resistance of various coatings after 3D printing. The use of both raw materials applied as thick films was successful; they retained their corrosion-resistant properties even with a change in their composition. Regarding the crystal structure, no difference was found between the base material and the material applied as a coating on the basis of X-ray diffraction investigations. Bulk HEA printing experiments need further optimization concerning their structural integrity and density in the case of the Cantor alloy. Bulk 3D printing experiments of the AlCrMnFeNi alloy did not yield satisfactory results because of the formation of dendritic microstructure and brittle BCC phase, and the residual internal stress resulted in part distortion and improper printing.

Open Access: Yes

DOI: 10.3389/fmats.2021.802076

Preparation of soft magnetic composite from Fe-6.9wt%Si by different heat treatment strategies.

I. Zsoldos L. K. Varga B. Kocsis

Publication Name: Iop Conference Series Materials Science and Engineering

Publication Date: 2020-08-25

Volume: 903

Issue: 1

Page Range: Unknown

Description:

Present study investigated the effect of isothermal heat treatment strategies between 800 °C and 1150 °C on the magnetic properties of toroidal samples made from Fe-6.9wt%Si powder. The samples were prepared by classical powder metallurgy method since the classical sheet forming methods no longer work with the high silicon content. Our results presented here are part of a series of comparative experiments where we study the effectiveness of the insulating layers created during and before the compacting of soft magnetic composites (SMCs). Our goal was to create a soft magnetic composite made of ferromagnetic and inorganic insulating material with a frequency limit already in the megahertz range and a Snoek limit of few gigahertz. In the case of samples made from Fe-6.9wt%Si powder, the computed tomography results showed that significant porosity is to be expected after pressing. Its positive effect occurred during the heat treatment in the atmospheric agent, where silicon is precipitated and deposited on the surface of the particle. This coating is an electrically insulating layer at the grain boundaries. Depending on the heat treatment strategy, 1 or 2 ferromagnetic phases were observed. The frequency limit approached the target values, but due to the low value of static permeability, the Snoek limit did not reach the gigahertz range. However, there is a significant improvement in magnetic properties compared to the heat-treated samples in a protective gas.

Open Access: Yes

DOI: 10.1088/1757-899X/903/1/012042

Metallographic and magnetic analysis of direct laser sintered soft magnetic composites

I. Fekete L. K. Varga B. Kocsis

Publication Name: Journal of Magnetism and Magnetic Materials

Publication Date: 2020-05-01

Volume: 501

Issue: Unknown

Page Range: Unknown

Description:

In this present study, soft magnetic composite samples were made from iron-silicon alloys. For the purpose of optimizing 3D printing parameters, preliminary experiments were performed. Metallographic and computed tomography investigations were used to determine the appropriate sintering settings. Besides the microscopic and CT analysis, considering the permeability spectra have been compared to the samples.

Open Access: Yes

DOI: 10.1016/j.jmmm.2020.166425

Soft Magnetic Composites Prepared by 3D Laser Printing

I. Fekete L. K. Varga István Hatos B. Kocsis

Publication Name: Acta Physica Polonica A

Publication Date: 2020-01-01

Volume: 137

Issue: 5

Page Range: 886-888

Description:

In this study, iron and inorganic insulator powders have been used for preparing soft magnetic metal-insulator type composites by 3D laser printing. These samples have been compared with those obtained by traditional pressing and sintering method. Considering the permeability spectra, an increase of the frequency limit has been found for the laser printed samples. In addition to the AC and DC magnetic parameters, the results of XRD and SEM investigations are also presented.

Open Access: Yes

DOI: 10.12693/APhysPolA.137.886