PSI - Issue 61

ScienceDirect Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2023) 000 – 000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2023) 000 – 000 Available online at www.sciencedirect.com Procedia Structural Integrity 61 (2024) 42–46

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2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of IWPDF 2023 Chairman 10.1016/j.prostr.2024.06.007 2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of IWPDF 2023 2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of IWPDF 2023 © 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of IWPDF 2023 Chairman Abstract Cold plastic deformations recognizably cause increasing lattice imperfections such as point defects and dislocations in the structure, which could then have an effect on diffusion characteristics of the material. In order to explore such an effect of flow forming, a flow formed AISI 4140 steel and an annealed 4140 steel were subjected to the HDA process in a molten Al7020 bath at 750  C for 4 min, and a subsequent diffusion annealing was performed at 800  C, and their coating characteristics such as coating thickness and hardness were compared. The results indicated that the coating thickness of the flow formed samples was higher (80  m) than that of the annealed sample (50  m) after the HDA process. Diffusion annealing increased the coating thickness of both samples five times, reaching 400  m and 250  m for the flow formed and the annealed samples, respectively. Comparing the measured thickness of the coatings revealed that flow forming accelerates diffusion during the HDA process, probably due to the defect structure induced by the flow forming. On the other hand, the coating hardness was in between 1000-1100 HV for both samples, implying that the initial condition of the sample does not have a remarkable effect on hardness after the HDA process. 1. Introduction Flow forming is a cold deformation technique for the manufacturing of axisymmetric components. During the flow forming, a rotating initial tube (preform) is pushed by rollers through the thickness direction of the tube. Flow-forming is highly used in aerospace and defense industry to manufacture rotating shafts, rocket motor cases and versatile tubes. In order to protect these parts from oxidation and corrosion, coating must be applied (Erdogan et al. 2023; Karakaş et al. 2021). Aluminum protects steel especially due to the instantaneous formation of a thin and compact oxide alumina film, which is practically insoluble in most common corrosive media. Diffusional coatings are applied by different types of coating technics such as cladding, brazing, welding, hot dipping and spray metallizing. Abstract Cold plastic deformations recognizably cause increasing lattice imperfections such as point defects and dislocations in the structure, which could then have an effect on diffusion characteristics of the material. In order to explore such an effect of flow forming, a flow formed AISI 4140 steel and an annealed 4140 steel were subjected to the HDA process in a molten Al7020 bath at 750  C for 4 min, and a subsequent diffusion annealing was performed at 800  C, and their coating characteristics such as coating thickness and hardness were compared. The results indicated that the coating thickness of the flow formed samples was higher (80  m) than that of the annealed sample (50  m) after the HDA process. Diffusion annealing increased the coating thickness of both samples five times, reaching 400  m and 250  m for the flow formed and the annealed samples, respectively. Comparing the measured thickness of the coatings revealed that flow forming accelerates diffusion during the HDA process, probably due to the defect structure induced by the flow forming. On the other hand, the coating hardness was in between 1000-1100 HV for both samples, implying that the initial condition of the sample does not have a remarkable effect on hardness after the HDA process. Keywords: Hot-dip aluminizing, Flow-forming, Microstructure 1. Introduction Flow forming is a cold deformation technique for the manufacturing of axisymmetric components. During the flow forming, a rotating initial tube (preform) is pushed by rollers through the thickness direction of the tube. Flow-forming is highly used in aerospace and defense industry to manufacture rotating shafts, rocket motor cases and versatile tubes. In order to protect these parts from oxidation and corrosion, coating must be applied (Erdogan et al. 2023; Karakaş et al. 2021). Aluminum protects steel especially due to the instantaneous formation of a thin and compact oxide alumina film, which is practically insoluble in most common corrosive media. Diffusional coatings are applied by different types of coating technics such as cladding, brazing, welding, hot dipping and spray metallizing. * Corresponding author. Tel.: +90 5384182551 E-mail address: aptullah.karakas@repkon.com.tr 3rd International Workshop on Plasticity, Damage and Fracture of Engineering Materials (IWPDF 2023) Hot-Dip Aluminizing of Flow-formed AISI 4140 Steel Aptullah Karakaş 1,2 and Murat Baydoğan 2 3rd International Workshop on Plasticity, Damage and Fracture of Engineering Materials (IWPDF 2023) Hot-Dip Aluminizing of Flow-formed AISI 4140 Steel Aptullah Karakaş 1,2 and Murat Baydoğan 2 1 Repkon Machine and Tool Industry, Istanbul 34980, Türkiye 2 Department of Metallurgical and Materials Engineering, Istanbul Technical University, Istanbul 34469, Türkiye 1 Repkon Machine and Tool Industry, Istanbul 34980, Türkiye 2 Department of Metallurgical and Materials Engineering, Istanbul Technical University, Istanbul 34469, Türkiye Keywords: Hot-dip aluminizing, Flow-forming, Microstructure * Corresponding author. Tel.: +90 5384182551 E-mail address: aptullah.karakas@repkon.com.tr