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Comparative studies on the microstructure and corrosion behaviour of forged and SLM processed 316L stainless steel

Authors: Dino Woelk, Norbert Kazamer, Gabriela Mărginean

Abstract

The corrosion behaviour of forged and SLM (Selective Laser Melting) processed 316L samples was investigated in a 3.5% NaCl solution at neutral and light acidic pH. The influence of the oxygen concentration in the testing solution on the corrosion resistance of the alloy was also proved. This made it possible to qualitatively evaluate the influence of the additive manufacturing process on the microstructure of the 316L alloy in comparison to that of the forged steel. Therefore, the logarithmic polarisation curves generated during the electrochemical investigations were compared, especially in respect to the corrosion potential respectively corrosion current density. The results showed that the corrosion resistance of the 3D-printed samples was inferior to that of the forged 316L. Instead of the pitting corrosion that often appears during exposure of the forged material to chloride containing media, the SLM processed material exhibited rather an extensive surface attack. The microscopic examination of the samples revealed large differences in porosity between the microstructures obtained by means of the two manufacturing methods, whereby the 3D-printed samples exhibited a larger number of voids.

Key words:selective laser melting, 316L, corrosion behaviour;

DOI: 10.24867/ATM-2021-1-001

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Porosity distribution in metal injection molded parts

Authors: Samir Butković, Emir Šarić, Muhamed Mehmedović

Abstract

Metal injection molding technology is commonly used in production of small and very complex parts. Residual porosity is unavoidable characteristic of P/M parts, affecting their final properties. During injection molding phase powder-binder separation can occur, causing green density variation through cross section of the part. This behaviour is particularly pronounced as complexity of the parts increases. As a consequence, zones with different density and residual porosity can be seen after sintering. In this regard, porosity and hardness distribution of the sintered ring-shaped part is analysed and presented in the paper.

Key words:Metal injection molding, sintering, porosity distribution;

DOI: 10.24867/ATM-2021-1-002

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Multi response parameters optimization of ZA-27 nanocomposites

Authors: Sandra Gajević, Slavica Miladinović, Onur Güler, Hamdullah Çuvalcı, Nenad Miloradović, Blaža Stojanović

Abstract

In this study, Taguchi-Grey relational analysis was used to investigate and optimize wear parameters such as sliding speed, reinforcement of Gr and reinforcement of Al2O3, and their effect on dry sliding wear performance of ZA-27 nanocomposites. Nanocomposites were synthesized via hot pressing process with pre-processing mechanical milling. Sixteen experimental tests were performed based on design of experiments which was created with the help of Taguchi L16 orthogonal array. Grey relational analysis (GRA) was applied for determination of optimal combination of parameters in order to improve tribological characteristics. Optimal combination of factors, obtained with Taguchi Grey relational analysis was sliding speed of 100 rpm, reinforcement content of 1 vol.% Gr and reinforcement content of 4 vol.% Al2O3. Validation of results was done by using Artificial Neural Network (ANN). Developed model had overall regression coefficient 0.99836, and output values showed good correlation with experimental results. Based on this research, it can be observed that nanocomposites with reinforcement of Gr and Al2O3 can be potentially employed in many industries as a good substitute for the base alloy. In addition, as a result of the analysis of the worn surfaces, it was determined that with the increase of the Al2O3 ratio, the hard Al2O3 nanoparticles turned the dominant wear mechanism into abrasive. Also, it was determined that the Gr nanoparticles appeared on the abrasive wear lines.

Key words:Hybrid nanocomposite, ZA27 alloy, wear loss, coefficient of friction, ANOVA, GRA, ANN;

DOI: 10.24867/ATM-2021-1-003

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The material selection of the heating plates used in the vulcanization process obtained using different MCDM methods

Authors: Jelena Mihajlović, Goran Petrović, Dušan Ćirić, Miloš Madić

Abstract

The material selection problem is one of the most important steps in the development process of a part of any subassembly assembly, machine, product, etc. The material selection process needs a systematic and time-consuming approach to choose the optimal material to satisfy the product’s requirements. That is to say, many confronting criteria and possible material types (alternatives) available, makes this problem Multi-Criteria Decision-Making problem (MCDM). This paper shows the applicability of the MCDM methodology in the material selection problem for steam heating plates for the vulcanization process used in the inner tube manufacturing process. Specifically, the criteria weights are obtained by CRITIC (Criteria Importance Through Intercriteria Correlation), ENTROPY and PIPRECIA (Pivot Pairwise Relative Criteria Importance Assessment) methods, while TOPSIS (Technique for the Order Preference by Similarity to Ideal Solution) method has been implemented in this process for evaluation and ranking of the possible alternatives (material types).

Key words:Material selection, CRITIC, ENTROPY, PIPRECIA and TOPSIS method

DOI: 10.24867/ATM-2021-1-004

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The influence of continuous casting technology on the cleanliness of carbon steel

Authors: Aida Imamović, Raza Sunulahpašić, Mirsada Oruč, Omer Kablar, Derviš Mujagić

Abstract

The influence of the production method, i.e. casting technology on the cleanliness and thus the quality of carbon steels is best determined through the presence and type of non-metallic inclusions. A large number of inclusions, especially oxide and complex ones, can significantly affect the mechanical properties of carbon steels and limit their application for the production of finished products.

This paper presents the influence of the presence, type and amount of non - metallic inclusions in B500B carbon steel according to ASTM / AISI produced by continuous casting technology without and with the application of stream protection.

Key words: carbon steel, continuous casting, non-metallic inclusions, stream protection

DOI: 10.24867/ATM-2021-1-005

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Influence of the polymer matrix type on cavitation resistance of composites

Authors: M. Dojčinović, M. Pavlović, S. Jezdimirović, B. Purić, A. Cvetković

Abstract

Cavitation resistance of polymer matrix / basalt powder composites was determined in this work. Two types of composites were tested: epoxy resin / basalt powder composite and polyester resin / basalt powder composite. In both cases, a basalt powder was used as reinforcement in the resin (grain size 20μm, in the amount of 15 wt%). An ultrasonic vibration method with a stationary sample was used to test the cavitation resistance of composites in laboratory conditions. The change in sample mass with test time was monitored to define cavitation rate. Scanning electron microscopy was used to monitor the morphology of composites surface damage.

Key words:cavitation, composite, cavitation damage;

DOI: 10.24867/ATM-2021-1-006

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