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Öğe Effect of powder-pack aluminizing on microstructure and oxidation resistance of wire arc additively manufactured stainless steels(Elsevier Science Sa, 2023) Gurol, Ugur; Altinay, Yasemin; Gunen, Ali; Bolukbasi, Omer Saltuk; Kocak, Mustafa; Cam, GurelThis study investigated the effect of powder-pack aluminizing treatment on the high-temperature oxidation of ER307 stainless steel components fabricated by wire arc additive manufacturing (WAAM) during isothermal oxidation at 1000 degrees C for 5 h, 25 h, and 50 h. Scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), X-ray diffraction (XRD), X-Ray fluorescence (XRF), nanoindentation testing, and oxidation testing were used to characterize the aluminized and non-aluminized samples produced by WAAM. The results showed that the powder-pack aluminizing increased the surface nano-hardness up to 13.95 GPa and the modulus of elasticity up to 159 GPa, as well as improving the microstructure of WAAM ER307 stainless steel. Indeed, aluminide coatings remained stable up to temperatures exceeding 1000 degrees C, and the growth of hematite, the main oxide phase, was inhibited by a preferential alumina growth (Al2O3), resulting in an improvement in oxidation resistance in the range of 46-70 %. In addition, owing to the advantages of low-temperature aluminizing, the microstructure, mechanical properties, and oxidation resistance of these alloys have been improved without causing sigma phase formations, which constitute a significant problem in high-temperature heat treatment of stainless steels.Öğe Improving oxidation resistance of wire arc additive manufactured Inconel 625 Ni-based superalloy by pack aluminizing(Elsevier, 2023) Bolukbasi, Omer Saltuk; Serindag, Tarik; Gurol, Ugur; Gunen, Ali; Cam, GuerelThe aluminide coating layer was formed on wire arc additive manufactured (WAAM) Inconel 625 (IN625) Ni-based superalloy by a pack-aluminizing process at 700 degrees C for 3 h. The aluminide coatings were evaluated utilizing X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and nanoindentation techniques. In addition, the oxidation performances of the aluminide coatings were compared with as-built WAAM IN625 samples based on their exposure in the open-air environment for 5, 25, and 50 h at 1000 degrees C. The aluminizing process provided a dense aluminide coating with a thickness of 35 mu m, continuous throughout the surface. The coating layer consists of mainly NiAl, Ni2Al3, Cr2Al, and MoAl5 phases and exhibited a nano-hardness of 12.85 +/- 0.43 GPa. Moreover, the applied heat treatment also improved the surface hardness and elasticity modules of WAAM Inconel 625. The stability of aluminide phases (NiAl, Ni2Al3) at temperatures exceeding 1000 degrees C and the formation of stable Al2O3 oxide islands on the surface provided 6.63 times, 2.70 times, and 2.65 times better oxidation resistance in the aluminized samples than the as-built WAAM IN625 in the 5 h, 25 h and 50 h oxidation periods at 1000 degrees C, respectively. In contrast, the increase in the oxidation time changed the oxidation mechanism of as-built WAAM IN625 from Cr2O3 to Cr2O3 and spinel phases such as NiCr2O4, NiMoO4, and NiO. On the other hand, the increase in the oxidation time in aluminized samples caused Kirkendall voids formation and their degradation. Therefore, it was concluded that the mechanical properties could be improved, and the oxidation resistance of these alloys could be improved with the aluminizing heat treatment.(c) 2023 CIRP.Öğe A new approach to improve some properties of wire arc additively manufactured stainless steel components: Simultaneous homogenization and boriding(Elsevier Science Sa, 2023) Gunen, Ali; Gurol, Ugur; Kocak, Mustafa; Cam, GurelArc-directed energy deposition (Arc-DED), also commonly referred to as wire arc additive manufacturing (WAAM), is a cost-effective 3D metal additive manufacturing process in which large metallic parts can be produced due to high deposition rates. Stainless steels, widely used in many areas due to their excellent corrosion resistance, are one of the most produced materials by the WAAM method. However, stainless steels have low surface hardness. Moreover, the high heat input in the deposition process in WAAM sometimes causes the mechanical properties of stainless steels to be lower than casting or wrought stainless steels. These considerations limit the use of WAAM stainless steels, especially in abrasive environments. For this purpose, 307ER stainless steel produced by WAAM method was subjected to homogenization and boriding process simultaneously at 1000 degrees C for 1 h and the effect of applied heat treatment on microstructure, phase components, hardness and wear resistance was investigated. The results showed that with the boriding process, a 30 mu m thick boride layer consisting of FeB, Fe2B, Cr5B3 and MnB phases with a hardness of 21.5 GPa and a modulus of elasticity of 310 GPa was formed in addition to the dissolution of interdendritic regions in the as-built structure and a complete homogenization of the microstructure. Furthermore, owing to the high hardness and elasticity modulus in addition to the boride layer's self-lubrication properties obtained on the WAAM samples surfaces, 31.84 times and 8.06 times increased in wear resistance at room temperature and 500 degrees C temperature, respectively, and a decrease in friction coefficients was obtained. Moreover, the results showed that the simultaneous homogenization and boriding processes of stainless steels produced by the WAAM method would improve their microstructure and tribological behavior. This way, these steels can be used in wider areas of application.