István Hatos

57193384609

Publications - 11

Effect of Energy Density on the Mechanical Properties of 1.2709 Maraging Steel Produced by Laser Powder Bed Fusion

I. Fekete Gusztáv Fekete István Hatos H. Hargitai

Publication Name: Materials

Publication Date: 2024-07-01

Volume: 17

Issue: 14

Page Range: Unknown

Description:

The unusual combination of the fundamentally contradictory properties of high tensile strength and high fracture toughness found in maraging steel makes it well suited for safety-critical applications that require high strength-to-weight materials. In certain instances, additive manufacturing (AM) has produced materials that may be desirable for safety-critical applications where impact toughness is a key property, such as structural parts for the aerospace industry or armor plates for military applications. Understanding the influence of process parameters and defect structure on the properties of maraging steel parts produced via laser powder bed fusion (LPBF) is a fundamental step towards the broader use of AM technologies for more demanding applications. In this research, the impact energy of V-notched specimens made of 1.2709 maraging steel produced by LPBF was determined via Charpy impact testing. Specimens were produced using different processing parameter sets. By combining the process parameters with the porosity values of the parts, we demonstrate that an almost full prediction of the impact properties can be achieved, paving the way for significantly reducing the expenses of destructive testing.

Open Access: Yes

DOI: 10.3390/ma17143432

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

Laser powder bed fusion and casting for an advanced hybrid prototype mold

Martin Zobač I. Fekete J. G. Kovács B. Zink István Hatos Dániel Török Tatyana Ageyeva Róbert Boros H. Hargitai

Publication Name: Journal of Manufacturing Processes

Publication Date: 2022-09-01

Volume: 81

Issue: Unknown

Page Range: 748-758

Description:

One of the factors limiting the throughput of injection molding is cooling time, which is the most significant part of the total cycle time. The cooling efficiency of molds can be considerably improved with additive manufacturing techniques. A 3D printed injection mold with conformal cooling channels reduces cooling time by 30–40 %. However, the cooling efficiency of these molds can be further improved with a multi-material approach and the use of materials with excellent thermal and mechanical properties. In this study, we propose a hybrid mold insert made of steel and copper, produced with the combination of Laser Powder Bed Fusion (L-PBF) and casting. The steel shell that contains conformal cooling channels was printed by L-PBF. Then this shell was cast with copper. We found that the hybrid mold insert we developed has lower residual cooling time and heat extraction is more uniform than the conventional printed steel insert. The developed hybrid mold insert enables a reduction of residual cooling time by 15 %.

Open Access: Yes

DOI: 10.1016/j.jmapro.2022.07.034

Influence of local porosity on the mechanical properties of direct metal laser-sintered 1.2709 alloy

I. Fekete István Hatos Dóra Harangozó H. Hargitai

Publication Name: Strojniski Vestnik Journal of Mechanical Engineering

Publication Date: 2020-01-01

Volume: 66

Issue: 6

Page Range: 351-357

Description:

Powder bed metal printing has demonstrated its potential for the direct manufacturing of complex parts. It has great flexibility compared to conventional manufacturing. There are also some difficulties and problems, e.g., because the process stops during production. When the process is restarted, the first layer may be thicker due to technological limitations. In this paper, the effects caused by the presence of these thicker layers were investigated. The possibility of re-melting the layers to reduce porosity were also analysed. A tool steel powder grade 1.2709 was used to produce samples with an increased thickness of melted layers.

Open Access: Yes

DOI: 10.5545/sv-jme.2020.6573

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

Conformal cooling with heat-conducting inserts by direct metal laser sintering

István Hatos B. Kocsis H. Hargitai

Publication Name: Iop Conference Series Materials Science and Engineering

Publication Date: 2018-11-30

Volume: 448

Issue: 1

Page Range: Unknown

Description:

With the development of layer manufacturing technologies injection mold inserts with conformal cooling channels can be manufactured. If the cooling channels can be placed along the geometry, the heat removal is uniform and effective. In tight mold regions, formation of cooling channel is not possible or not efficient. The combination of conformal cooling and heat conductive insert can be an ideal solution for the effective cooling.

Open Access: Yes

DOI: 10.1088/1757-899X/448/1/012027

Effect of locally increased melted layer thickness on the mechanical properties of laser sintered tool steel parts

I. Fekete T. Ibriksz István Hatos András Lajos Nagy B. Kocsis H. Hargitai

Publication Name: Iop Conference Series Materials Science and Engineering

Publication Date: 2018-10-18

Volume: 426

Issue: 1

Page Range: Unknown

Description:

Additive technologies have several advantages over conventional manufacturing, such as the freedom of geometry of the products and internal structures. There are also some limitations and problems, deriving from stopping the process during the production. By restarting the process, the building often continues with a thicker starting layer due to the deposition of two or more layers. The effect of skipped melting of layers is investigated in this paper. Maraging steel powder (MS1) was used in direct metal laser sintering (DMLS) process to produce samples with increased thickness of melted layers. The layer thickness was increased in 20 μm steps up to 160 μm with 0.5 mm offset between the increased thickness layers. Porosity caused by the uneven melting was measured by optical microscope, mechanical tests were carried out to quantify the effect of skipped layers and fractured surfaces were observed under SEM. We have found that the yield strength and tensile strength are not affected if the layer thickness is slightly increased locally in the laser sintered part, while even a small increase in porosity greatly reduces the total elongation of the specimen. The decrease of impact energy due to the porosities shows similar correlation with the decrease of percentage elongation at break. However, the Charpy impact test is much more sensitive to layer skipping, the lack of melted layers lowers the impact strength significantly.

Open Access: Yes

DOI: 10.1088/1757-899X/426/1/012014

Surface modification and wear properties of direct metal laser sintered hybrid tools used in moulds

I. Fekete J. G. Kovács T. Ibriksz Mária B. Maros István Hatos H. Hargitai

Publication Name: Journal of Mechanical Engineering

Publication Date: 2018-01-01

Volume: 64

Issue: 2

Page Range: 121-129

Description:

Injection moulding is one of the most productive plastic forming processes. Product development and the reduction of production time require new solutions in tooling design and manufacturing. Direct metal laser sintering (DMLS) allows moulds to be built with special cooling systems, which offer curved cooling lines that can follow the geometry of the part (conformal cooling). One disadvantage of DMLS, its high cost, can be dramatically reduced with the building of hybrid structures. With conventional tool steels as the base plate and only the special geometry of the part sintered on the top, the final geometry can be manufactured after sintering by conventional process technologies. We produced hybrid structures by direct metal laser sintering maraging steel (MS1) powder onto the surface of commercial mould steels and studied the effect of different heat treatments on porosity, tribological behaviour and the microstructure. The transition zone was also characterized.

Open Access: Yes

DOI: 10.5545/sv-jme.2017.4942

Characterization of internal stresses in hybrid steel structures produced by direct metal laser sintering

J. G. Kovács István Hatos H. Hargitai

Publication Name: Materials Science Forum

Publication Date: 2017-01-01

Volume: 885

Issue: Unknown

Page Range: 196-201

Description:

In this study hybrid structures were produced by direct metal laser sintering of maraging steel (MS1) powder onto the surface of commercial mold steels. The over-sintering method should be analyzed to find the optimum pre- and post-heat treatment to minimize the internal stresses. The internal stress is directly proportional to the deformation if the solid thick part is reduced to thin plate like parts. Based on this recognition the deformation of the plates over-sintered with MS1 could be analyzed in order to explore the internal stresses and the effect of different pre- and postheat treatments were examined.

Open Access: Yes

DOI: 10.4028/www.scientific.net/MSF.885.196

Enhanced injection molding simulation of advanced injection molds

N. K. Kovács A. Suplicz J. G. Kovács T. Tábi B. Zink István Hatos H. Hargitai F. Szabó

Publication Name: Polymers

Publication Date: 2017-01-01

Volume: 9

Issue: 2

Page Range: Unknown

Description:

The most time-consuming phase of the injection molding cycle is cooling. Cooling efficiency can be enhanced with the application of conformal cooling systems or high thermal conductivity copper molds. The conformal cooling channels are placed along the geometry of the injection-molded product, and thus they can extract more heat and heat removal is more uniform than in the case of conventional cooling systems. In the case of copper mold inserts, cooling channels are made by drilling and heat removal is facilitated by the high thermal conductivity coefficient of copper, which is several times that of steel. Designing optimal cooling systems is a complex process; a proper design requires injection molding simulations, but the accuracy of calculations depends on how precise the input parameters and boundary conditions are. In this study, three cooling circuit designs and three mold materials (Ampcoloy 940, 1.2311 (P20) steel, and MS1 steel) were used and compared using numerical methods. The effect of different mold designs and materials on cooling efficiency were examined using calculated and measured results. The simulation model was adjusted to the measurement results by considering the joint gap between the mold inserts.

Open Access: Yes

DOI: 10.3390/polym9020077

Understanding and analyzing the effect of residual stresses in direct metal laser sintering through optical deformation measurement

Zoltán Weltsch István Hatos Valentin Szabó

Publication Name: Progress in Additive Manufacturing

Publication Date: 2025-01-01

Volume: Unknown

Issue: Unknown

Page Range: Unknown

Description:

Residual stresses are one of the main challenges in metal additive manufacturing, particularly in direct metal laser sintering (DMLS). These stresses often lead to deformation once parts are removed from the build plate. In this study, we investigated the causal relationship between internal stresses and deformation behavior using a specially designed twin-cantilever geometry. This setup allowed parallel evaluation of different stress-relief treatments on a single component while minimizing cross-effects. High-precision optical 3D scanning was used to measure full-surface deformations before and after support removal and stress-relief heat treatment. The 1.2709 maraging steel (X3NiCoMoTi18-9-5) specimens were produced using a DMLS process with standard parameters, and stress-relief annealing was performed at 600 °C for 24 h. Results show that the heat treatment significantly reduced distortion on the supported side of the parts, with changes under 5%, while unsupported regions showed increased deformation, exceeding 60% in some cases. This indicates that internal stresses remain largely intact during heating and can further distort softened material if not mechanically constrained. The study confirms the critical role of constraint during heat treatment and demonstrates that optical metrology offers a reliable method to evaluate deformation trends. The results provide important insights into stress management strategies for DMLS parts and highlight the limitations of thermal relief in unconstrained geometries.

Open Access: Yes

DOI: 10.1007/s40964-025-01371-3