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Öğe Characterization and fracture toughness evaluation of the thick-walled wire arc additively manufactured low alloy steels(Springer Heidelberg, 2023) Dagyikan, Kadir; Gurol, Ugur; Kocak, MustafaWire arc additive manufacturing (WAAM) has recently gained great attention in producing metallic parts due to significant cost savings, high deposition, and its convenience. However, there is still limited knowledge concerning testing for mechanical properties of the WAAM-produced steel parts using different welding wires. This paper presents the results of the extensive experimental study aimed at assessing the mechanical properties of the WAAM-produced multi-pass thick-walled steel parts using two different ER70S-6 and one ER110S-G welding wires. This study focused on revealing the role of the microstructure on the fracture toughness values, which were obtained from the specimens extracted in two directions, namely, transversal direction (T) and longitudinal direction (L) according to the deposition direction. Before extraction of the toughness specimens, the computed radiography (CR) tests were performed to detect if any welding defects occurred during the layer deposition. Next, the microstructural features of the thick-walled WAAM parts were characterized by stereo microscopy (SM), optical microscopy (OM), and scanning electron microscopy (SEM). Finally, the mechanical properties of the part were evaluated by Charpy V-notch (CVN) impact toughness, tensile, and hardness tests. The results exhibit an anisotropic material behavior in as-built conditions for each filler metal. Therefore, careful consideration of notch orientations and their effects on mechanical properties is important in assessing the fitness-for-service performance of the WAAM-produced low-alloyed steel parts.Öğe Characterization of a low-alloy steel component produced with wire arc additive manufacturing process using metal-cored wire(Walter De Gruyter Gmbh, 2022) Gurol, Ugur; Dilibal, Savas; Turgut, Batuhan; Kocak, MustafaIn this study, a low-alloy steel component was manufactured using specially produced E70C-6M class of metal-cored welding wire according to AWS A5.18 standard for the WAAM process. The manufactured low-alloy steel component was first subjected to radiographic examination to detect any weld defect. Uniaxial tensile tests were conducted for the bottom, middle and upper regions. The micro-hardness tests were performed parallel to the deposition direction. The results show that microstructures varied from base metal to the face region of the WAAM component, including the bottom, middle and top sections. The bottom region showed lamellar structures; the middle and upper region presented equiaxed ferrite structure with a small amount of grain boundary pearlites and the face region displayed a mix of equiaxed and lamellar structures of ferrites. The yield and ultimate tensile strengths of the top, middle, and bottom regions exhibited similar results varying between 370 MPa and 490 MPa, respectively. In contrast, the top region showed an elongation value about 15% higher than other regions. Moreover, the yield and ultimate tensile strength for WAAM-produced component were found to be 14% and 24% lower than the multiple-pass all-weld metal of E70C-6M class of metal-cored wire.Öğe Characterization of Armour Steel Welds Using Austenitic and Ferritic Filler Metals(Springer India, 2022) Gurol, Ugur; Karahan, Tuba; Erdol, Sevim; Coban, Ozan; Baykal, Hakan; Kocak, MustafaIn this study, fillet welding processes were performed on high strength Miilux Protection 500 (MIL-A-46100) steel, which is used as armour material in defence industry, using GMAW method with austenitic ER307 and ferritic ER110S-G filler metals. The characterization of welded structure was carried out by performing elemental mapping processes as well as microstructural examination and microhardness tests. Results showed that hardness of weld metal was found to be 46% and 78% of the base metal hardness for austenic and ferritic filler metal, respectively. The fine-grained heat-affected zone was found to be the highest hardness while intercrital heat-affected zone was found to be lowest hardness through heat-affected zone. The smoother decrease was obtained in the softening zone with austenitic filler metal due to lower thermal conductivity. Consequently, the hardness values at a distance of 6 mm from the plate edge for both filler metals reached the hardness of base metal and both welded structures met the minimum requirements of the military standards.Öğe Characterization of Fillet Welded Armor Steel Performed by Robotic Gas Metal Arc Welding: Effect of Heat Input on Microstructure and Microhardness(Springer, 2023) Coban, Ozan; Kaymak, Fatih; Gurol, Ugur; Kocak, MustafaIn this research, fillet welding was conducted on 8-mm thick Miilux OY Protection 600 (MIL-A-46100) armor steel using AWS A5.9 GeKa ER307 austenitic filler wire. The welding process involved robotic MIG/MAG with five different heat inputs ranging from 0.3 to 1.2 kJ/mm. The study focused on examining the influence of heat input on the microstructure, elemental changes, microhardness, and dimensions of the weld metal and the heat-affected zone (HAZ). These investigations were conducted to determine the welding parameters that they satisfy the quality requirements of the MIL-STD-1185 standard for this steel grade and weld consumable. Through analysis of macrostructure, microstructure, and microhardness, it was observed that increasing the heat input led to a decrease in hardness for both the weld metal and the HAZ, while expanding the HAZ width. The weld metal exhibited a homogenous hardness distribution at lower and higher heat inputs, but hardness increased from the root to the face for both heat inputs of 0.5 and 0.7 kJ/mm welds. Notably, a significant decrease in hardness occurred in the transition of partial transformation region (intercritical HAZ) and tempering region (subcritical HAZ) for heat inputs above 0.7 kJ/mm, indicating softening. Moreover, the width of the subcritical heat-affected zone substantially increased. Evaluation of the distance required to reach base metal hardness from the welding toe revealed that a heat input of 1.2 kJ/mm exceeded the maximum requirement of 15.9 mm according to the MIL-STD-1185 standard. However, the requirements of the military standard were satisfied for other heat input values. These findings were associated with microstructural changes in grain size, martensite, bainite, martensite/austenite morphology and their fractions, as well as delta ferrite morphology. The results successfully demonstrated that robotic GMAW welding can be applied using lower strength (undermatched) filler metal to satisfy the requirements of the respective standard of MIL-STD-1185.Öğe A comparative study on the microstructure, mechanical properties, wear and corrosion behaviors of SS 316 austenitic stainless steels manufactured by casting and WAAM technologies(Elsevier, 2023) Gurol, Ugur; Kocaman, Engin; Dilibal, Savas; Kocak, MustafaReplacing the traditional casting method with wire arc additive manufacturing (WAAM) to produce complex shaped parts will lead to using cost-effective technology even for challenging engineering applications depending on their geometry and number of the parts to be produced. This work performed a comparative study on the stainless steel 316 parts manufactured by WAAM and sand casting to reveal the microstructural, mechanical, wear, and corrosion behaviors. The WAAM components were manufactured using three different cooling dwell times and compared in terms of microstructures with the as-cast and heat-treated cast parts to reveal the properties of the WAAM parts. It was concluded that WAAM is a viable engineering alternative to the casting technology. Results showed that the WAAM and cast parts revealed similar microstructures, including delta ferrite and austenite phases, but the cast parts had a coarser grain and lower amount of delta ferrite due to slower cooling during the solidification. The yield and tensile strength of WAAM parts showed an increasing trend with the increase in dwell time, and on average, their yield strength was similar to 1.5 times higher than in cast parts due to the smaller grains and more elevated delta-ferrite content resulting from rapid cooling. Furthermore, the greatest wear resistance was obtained in the cast parts after solution annealing heat treatment followed by water quenching. In contrast the highest corrosion resistance was obtained from WAAM parts produced using a dwell time of 120 sec. In conclusion, WAAM technology can be an excellent alternative to casting technology for producing stainless-steel parts with optimized process parameters.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 Effect of the notch location on the Charpy-V toughness results for robotic flux-cored arc welded multipass joints(Walter De Gruyter Gmbh, 2022) Gurol, Ugur; Coban, Ozan; Cosar, Ibrahim Can; Kocak, MustafaIn this study, the effect of the notch locations on the Charpy-V toughness values of the all-welded joint obtained using robotic flux-cored arc welding was investigated with respect to microstructures at the notch locations. Charpy impact tests were performed through the thickness with notch location at the centerline as well as off-set regions of the weld metal in addition to the microhardness measurements conducted. The detailed weld metal characterization was conducted using a stereo microscope, optical microscope, and scanning electron microscope at the same location where the Charpy tests and microhardness tests were performed. The sub-zero impact toughness test results indicated that the columnar weld metal regions exhibited low toughness values while the centerline microstructure consisting of mainly reheated regions displayed much higher toughness values even at the test temperature of -60 degrees C, satisfying the toughness requirement of the requested 47 J value. It is concluded that a small variation of the through-thickness notch position may result in different toughness values for the same weld metal. On this basis, the notching procedure of the Charpy-V samples for the multi-pass weld metal should be conducted with care and obtained results should be explained with respective notch position and microstructure.Öğe Fabrication and Characterization of Wire Arc Additively Manufactured Ferritic-Austenitic Bimetallic Structure(Korean Inst Metals Materials, 2023) Gurol, Ugur; Turgut, Batuhan; Kumek, Hulya; Dilibal, Savas; Kocak, MustafaBimetallic parts are used in many industrial fields, such as pressure vessels, shipbuilding, aerospace, and automotive industries. Conventional bimetallic part production involves a combination of two different metals that are joined using welding and brazing operations. Additive manufacturing technologies offer a cost-effective and innovative manufacturing alternative for complex 3D-shaped parts that can have multi-material designs for better structural performance. However, the structural performance of bimetallic components is primarily influenced by the combination of the employed materials, the interface's morphology, and interface bonding strength. This work investigated the microstructure and mechanical behavior of a bimetallic thick-walled structure as WAAM Wall fabricated by depositing low-alloyed metal-cored wire on the top of 316L stainless steel by robotic wire arc additive manufacturing (WAAM) process. The results showed that both low-carbon steel and austenitic stainless steel SS316L wires are suitable for manufacturing defect-free bimetallic WAAM components, which may widen the design flexibility to manufacture bi-metallic and or functionally graded WAAM components. However, detailed microstructural characterization indicated that martensitic microstructure containing chrome carbides was developed at the bimetallic interface due to an increase in Ni and Cr contents, resulting in a sudden increase of 95% in hardness and a sharp decrease of 70% in fracture toughness at the interface region compared to the SS 316L side. This high-hardness region also resulted in an increase of about 113% and 86% for yield and tensile strengths and a sharp reduction of 69% for elongation values in horizontal interface specimens compared to vertical interface specimens.Öğe Investigation of the microstructural and mechanical properties of welding joints made with underwater electrodes(Gazi Univ, Fac Engineering Architecture, 2022) Gurol, Ugur; Baykal, Hakan; Yildiz, N. Benuse; Yilmaz, Can; Daniskan, Omur; Kocak, MustafaIn this study, the metallurgical properties of all-weld-metal, which welded underwater and atmospheric conditions by using rutile-based electrodes and low alloy S355J2+N steel plates, were investigated. Underwater welding process were performed at a depth of 4 meters in the open sea with paraffin coated GeKaTec UW E7014 underwater electrodes that specially developed according to the AWS A5.35 standard for the first time in Turkey. The welded plates were firstly subjected to non-destructive tests according to the AWS A5.35 standard. Then, tensile test, Charpy-V impact test, hardness test and microstructure examinations were carried out to determine the mechanical properties and to identify the effects of sea water on the microstructural transformation. The results showed that there was no significant change in the yield and tensile strengths of the welds performed in both environments. However, compared to the welds performed at atmospheric conditions, it was observed that the welds performed underwater were 6-8% harder and the Charpy impact values obtained at-2 degrees C together with the % elongation values were lower by 48% and 22%, respectively. As a result, it has been observed that welds made underwater met with the requirements of AWS A5.35 standard quality Level 1.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.