PSI - Issue 61

Aptullah Karakaş et al. / Procedia Structural Integrity 61 (2024) 42 – 46 Aptullah Karakas/ Structural Integrity Procedia 00 (2019) 000 – 000

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Hot dip aluminizing (HDA) is one of the most important commercial process for aluminizing of steel, because it is the most economical process among aluminizing processes for the mass production of aluminized steel (Bahadur 2012). There are two types of hot dip aluminizing methods according to ASTM A463/A463M such as type 1 for high temperature oxidation resistance and type 2 for corrosion resistance. Hot dip galvanizing process is mostly applied for corrosion resistance. However, it is not suitable for high temperatures and upper temperature limit is 200  C. Therefore, Type 2 hot dip aluminizing may provide an alternative for the applications that require improved corrosion resistance (Dey et al. 2023). HDA is highly used in industry being a promising alternative to other methods such as galvanizing, nickel or chrome plating and physical vapor deposition because it is a cost effective method and can be completed in a very short process time. Hot dip aluminizing (HDA) is also effectively used at elevated temperatures because aluminide phases like FeAl, Fe 2 Al 5 and Fe 3 Al have high melting points and highly resistant to high temperature oxidation (Dey et al. 2023; Yürektürk and Baydoğan 2018). Flow-forming is a cold plastic deformation process to form symmetrical parts. Deformation hardening effect of the flow-forming process is one of the advantages and AISI 4140 Cr-Mo steel is used in flow-forming processes especially for defense industry (Yazgan et al. 2023). Dislocations are generated during cold plastic deformation of metals such as flow forming process. The amount of vacancies and line defects increase and accelerate diffusion of atoms. Therefore, it is expected that coating thickness must be thicker after hot dip aluminizing of flow-formed specimen in comparison with non-flow formed specimen (Yu et al., 2023; Verhoeven, 1989). Therefore, in this study, potentiality of hot dipped aluminizing of a flow formed AISI 4140 steel was investigated. 2. Experimental Procedure Flow-forming processes were first carried out on annealed AISI 4140 steel preforms with 55% thickness reduction ratio. Secondly, the specimens were taken from the preform and the flow-formed tubes by EDM with the dimensions of 30x30x3 mm for hot dip aluminizing. For this purpose, the specimens were ground with 180 grid sandpaper and then hold in ultrasonic bath 2 minutes for surface cleaning. Subsequently, the specimens were immersed into Al7020 alloy bath at 750  C, hold in the bath for 4 min. and then removed from the bath and cooled in air to the room temperature. Diffusion annealing was performed at 800  C. After the aluminizing was completed, the specimens were

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Figure 1: (a) Preform and flow-formed tubes; (b) aluminized samples.