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Consideration of Absorption Coefficient Changes in Numerical Simulations of Laser Forming

Authors: Helge Kügler, Frank Vollertsen

Abstract

Material processing with laser beams is well-known in nowadays production. Compared to CO2 lasers, modern solid state lasers are, amongst others, popular because of higher energy efficiency and higher absorption when metals like steel and aluminum are irradiated. However, the absorption of metals is not only dependent on the chemical composition of the work piece metal and the laser beam wavelength. Previous investigations determined the oxidation of the surface as an influence on laser beam absorption changes due to multiple irradiation. In this study, a method is presented for considering the absorption coefficient changes caused by surface oxidation in numerical simulations. Reproductions of single trajectories were assigned with appropriate absorption coefficients calculated from a function generated by reference tryouts. With the described approach, benefits are gained for numerical simulations of laser beam forming (like bending) and other processes with an iterative heat input.

Key words: laser bending; absorptivity; iterative processes; simulation accuracy

DOI: 10.24867/ATM-2019-1-001

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The effect of friction stirs welding speed on microstructure, mechanical properties and IGC of EN AW-5083 plates

Authors: Miloš Pavlović, Ljubica Radović, Igor Radisavljević, Nenad Radović

Abstract

The aim of this work was to evaluate the influence of welding speed on microstructure, mechanical properties, as well as Intergranular corrosion (IGC) susceptibility of EN AW-5083 alloy welded using FSW. FSW was performed using constant rotation speed of 750 rev/min, while welding speed was varied from 73 mm/min, 150 mm/min to 190 mm/min. Results show that increase of welding speed lead to decrease of the size of the nugget. This behavior is attributed to decrease of heat input during welding. Accordingly, lower grain size provides increase of the strength. All tested welds are resistant to IGC, evaluating by mass loss according to NAMLT test, and resistivity slightly decrease with increasing welding speed.

Key words: friction stir welding, EN AW-5083 alloy, welding speed, heat input; microstructure, mechanical properties.

DOI: 10.24867/ATM-2019-1-002

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Microstructural Analysis of Inconel 625 Nickel Alloy / UNS S31803 Duplex Stainless-Steel Dissimilar Weldments

Authors: Tuba Karahan, Tolga Mert, Mustafa Tümer, Zaim Mithat Kerimak

Abstract

In this study, Inconel 625 nickel alloy and UNS 31803 duplex stainless steel (DSS) dissimilar pairs were welded with MIG welding process. Weld metal, obtained with ERNiCrMo-3 filler wire, was subjected to mechanical and microstructural investigations. Notch impact test and micro hardness measurements were realized on weld metal in order to evaluate31803 mechanical properties. Microstructural changes in fusion line of the base metals were examined using optical and electron microscopes. Phase precipitations rich of Ti and Mo elements were detected among dendritic austenite arms in the weld metal. It was observed that ERNiCrMo-3 filler metal had sufficient toughness because of high nickel content.

Key words: Inconel, duplex stainless steel, toughness, hardness, microstructure

DOI: 10.24867/ATM-2019-1-003

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Influence of cutting parameters on the quality of the cut surfaces of steel swith a laser beam

Authors: Dobre Runchev, Filip Zdraveski, Irena Ivanova

Abstract

The main objective of the research covered in this paper is to present results for the quality of surfaces thermally cut with a laser beam. The variety of steel materials used as samples on which laser cutting is performed are the following Č.0146 (1.0330), Č.0147 (1.0333), Č.2131 (1.5024), SS Ferbec CR, HARDOX 450 and HARDOX 550. Thermal cutting is carried out with a CNC controlled Fiber laser BAYKAL type BLS–F–1530. The quality of the cut surface is analyzed based on varying the power of the laser beam, changing cutting speed and the type of additional gas (oxygen, air and nitrogen). By visual inspection, measuring the roughness of the cut surface and measuring the width of the intersection, it is determined the influence of the factors like type of the base material, type of gases, the power of thelaser beam and the cutting speed, in accordance with the standards DIN EN ISO 9013-2002 and the JUS C.T3.022.

Key words: Laser cutting, cut surface, roughness measurement;

DOI: 10.24867/ATM-2019-1-004

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Rapid Prototyping of Art Sculptural Shapes According to the Sample

Authors: Sasa Zivanovic, Slobodan Tabakovic, Sasa Randjelovic

Abstract

The aim of this paper is to spread the use of Rapid Prototyping technology (RP) - Additive Manufacturing (AM), into design, restauration and making Art sculptural shapes according to the sample. Rapid prototyping is being used since its origin in designers’ fields for a product design, and here it is presented in art design according to the sample, and it has been proved that it is a crucial tool in any design process. In this paper presents a procedure for the rapid prototyping of two models of monuments, the preparation of the model in the STL format and the making of scaled real models of the monuments.

Key words: rapid prototyping-additive manufacturing; art sculptural shape; programming; verification; simulation;

DOI: 10.24867/ATM-2019-1-005

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Influence of HVOF deposition thickness on adhesion strength of WC–CrC–Ni coatings

Authors: Alin Constantin Murariu, Ion Aurel Perianu

Abstract

In this paper, adhesion strength of WC–CrC–Ni coatings obtained by HVOF thermal spraying process of WOKA7504 powder has been studied in correlation with deposition thickness, chemical and structural properties. Besides the parameters strictly related to the process, deposition thickness was found to be the most significant factor affecting the adhesion strength. In the frame of experimental program 304L stainless steel and S235JR structural steel were used as substrate. Mechanical tests, SEM and EDX analysis, have been performed in order to assess structural and mechanical properties, phase composition of the deposited layers. Maximum average adhesion strength has been experimentally found of 23.4 N/mm2 for stainless steel and of 35.8 N/mm2 for structural steel, for a deposition thickness of 220 µm, achieved in two layers. Once the coatings’ thickness increases, the adhesion strength decreases constantly and over thickness of 400 to 650 µm, the existing coating imperfections and elongated carbides placed in the interlayer interface area could fail due to the thermal stresses during the HVOF thermal spraying process, since they are brittle stress concentrators and thus leading tocracking of coatings at small loads, since the coating layershave high hardness of 990 to 1151 HV 1.

Key words: protective coatings, tungsten carbide, HVOF, adhesive strength, failure mechanism

DOI: 10.24867/ATM-2019-1-006

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Performance Evaluation of the Effects of Post Weld Heat Treatment on the Microstructure, Mechanical and Corrosion Potentials of Low Carbon Steel

Authors: Isiaka Oluwole Oladele, Davies Babatunde Alonge, Timothy Olakunle Betiku, Emmanuel Ohiomomo Igbafen1, Benjamin Omotayo Adewuyi

Abstract

The effect of Post Weld Heat Treatment (PWHT) on the microstructure, mechanical and corrosion properties of low carbon steel have been investigated. The welding process was conducted on butt joint using Manual Metal Arc Welding (MMAW) techniques at a welding voltage of 23 V and welding current of 110 A with the use of E6013 and 3.2 mm diameter as filler material. Heat treatment through full annealing was carried out on the welded low carbon steel. The mechanical properties (hardness, impact toughness and tensile properties) of the AW and PWHT samples were determined. The microstructure of the AW and PWHT samples was characterized by means of an optical microscopy. Corrosion behavior of the sample was studied in3.5 wt.% NaCl environment using potentiodynamic polarization method. The results showed that the AW samples has good combination of mechanical and corrosion properties. The microstructure revealed fine grains of pearlite randomly dispersed in the ferrite for the AW base metal (BM) sample while agglomerated and fine particle of epsilon carbide or cementite randomly dispersed on the ferritic phase of the heat affected zone (HAZ) and weld metal (WM), of the AW, respectively. The PWHT samples shows that the annealing process allow diffusion and growth of the fine grains into partial coarse grains of ferrite and pearlite which did not encourage improvement of the properties. Therefore, it was concluded that the welding parameters put in place during welding of the low carbon steel are optimum for quality weld.

Key words: low carbon steel; welding; post weld heat treatment; mechanical properties; microstructure; corrosion behaviour.

DOI: 10.24867/ATM-2019-1-007

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