The stainless steel 304L (commercially supplied) and Monel K-500 that was prepared through cold pressing of metal matrix composite materials powder mixtures were joined by diffusion welding. Welding was performed under uniaxial compression using the 50 µm-thick nickel (Ni) and aluminum (Al) 2024 interlayers under 3 MPa at 950–980°C for 60 min in an argon gas atmosphere. After welding, the diffusion and intermediate zones of the samples were characterized using X-ray diffraction, optical microscopy, scanning electron microscopy, and energy-dispersive spectrometry analysis. As evaluating the diffusion zone with interlayer, it was determined that different interlayers expanded due to increasing temperature of the diffusion area. Interlayers expanded more on the K-500 side and relatively less on the 304L side. On the other hand, when samples with Ni interlayers were examined, high amount of Ni contained by both base material (304L) and interlayer led to the formation of rich Ni phases in the diffusion side. The brittle FeNi, Fe ₃ Ni ₂ , CuNi, Cu ₉ Si, Cu _0,81 Ni _0,19 , Fe _0,64 Ni _0,36 , CrNi, Cr ₂ Ni ₃ , FeNi ₃ , FeCu ₄ , and Al _0.71 Cr _0.3 Fe _17.65 , which were identified to form irregularity in the diffusion zone. These intermetallic phases increased the hardness and significantly decreased the ductility of different material couples joined by diffusion welding. As a result, the microhardness and lap shear tests were applied to specimens to characterize the mechanical properties of the joint zones. The maximum hardness and maximum lap shear values were obtained at joint that made with the Al interlayer at 980°C as 432.8 HV and 165 MPa.

Due to its super plasticity, low weight, and high mechanical resistance properties, generally, Ti6Al4V is used for aeronautical applications. However, it has low resistance to plastic shearing. In addition, it has poor wear resistance. For these reasons, a lot of techniques have been developed to improve its wear resistance. Investigations of microstructure and interfacial reactions of diffusion bonding of Ni and Ti6Al4V materials have been performed experimentally. Ni samples were prepared with 50 ± 5 µm Ni powders in cylindrical shape. For diffusion bonding, Ag foil was used for improving the interlayer and connection quality. Nickel and its alloys can be joined by using some different processes, and the use of an interlayer can further facilitate the joining process and improve the joint quality. The experiments were carried out under the protected atmosphere. Argon gas was used for protection. The experiments were performed under 5 MPa pressure for 60 min duration at 850 °C, 900 °C, and 950 °C thermal conditions. Investigations of metallurgical structure occurring in the interface areas were examined by optic analysis of EDS, SEM, and X-ray. The strength of the joints was tested by lap-shear tests. From observations, the best quality of the coalescence at interfaces was indicated at elevated temperatures.

Purpose: The purpose of this paper is to investigate interface characterization of CO₂ laser welded AISI 304 austenitic stainless steel and AISI 1010 low carbon steel couple. Laser welding experiments were carried under argon and helium atmospheres at 2000, 2250 and 2500 W heat inputs and 200‐300 cm/min welding speeds.Design/methodology/approach: The microstructures of the welded joints and the heat affected zones (HAZ) were examined by optical microscopy, SEM, EDS and X‐Ray analysis. The tensile strength of the welded joints was measured.Findings: The result of this study indicated that the width of welding zone and HAZ became much thinner depending on the increased welding speed. On the other hand, this width widened depending on the increased heat input. Tensile strength values also confirmed this result. The best properties were observed at the specimens welded under helium atmosphere, at 2500 W heat input and at 200 cm/min welding speed.Originality/value: There are many reports which deal with the shape and solidification structure of the fusion zone of laser beam welds in relation to different laser parameters. However, the effect of all influencing factors of laser welding has up to now not been extensively researched. Much work is required for understanding the combined effect of laser parameters on the shape and microstructure of the fusion zone. This paper, therefore, is concerned with laser power, welding speed, defocusing distance and type of shielding gas and their effects on the fusion zone shape and final solidification structure of some stainless steels.

GR5 (Ti6Al4V) is a material commonly used in aerospace and space, biomedical and automobile sectors, consisting of pure titanium at a minimum of 99% purity. Besides being lightweight, GR5 is separate from similar materials with its ability to resist corrosion at high levels and show high strength. SX steel is high silicon-content austenitic stainless steel with the ability of good quality of welding and excellent corrosion resistance in high concentration sulfuric acid and nitric acid. SX is used in areas such as acid coolers, acid piping systems, acid distributors, acid towers and tanks, pumps, nozzles, internals, strainers and mesh pads. With improving technology, the need for steel-titanium materials that are resisted to acid and made with welded joint is increasing. In this study, the effect of GR and SX materials of welding temperature on the connection is examined with diffusion welding method using copper intermediary layer. The material pairs are combined with a pressure of 5 MPa and a fixed welding time of 60 minutes in an argon gas environment in a silicon bar oven at the temperature of 980, 1000 and 1020°C. The SEM-EDS-AFM analysis of the combined samples is performed, the metallographic structure of the intermediary layer in the diffusion-affected region is examined by the optical microscope, and the possible phases are tried to be determined by the XRD analysis. The micro stiffness values of the connection area are analyzed.

SX steels, a type of stainless steel enriched with high silicon content, are frequently used in critical applications of the industry due to their resistance to many acids. Areas of use are acid tanks, acid coolers, acid pipe systems and acid radiators. Increasing areas of use have increased the need to combine with different materials. This study aimed to join the different layers by diffusion welding method using Cu, Ni, Al7072 and Al8079. The samples were combined by keeping them under 5MPa pressure for 60 minutes at 1000 °C in an argon gas environment. Phase changes occurring in the junction area due to the effect of different interlayers were tried to be determined by SEM-EDS and XRD analyses. The changing metallographic structure of the intermediate layers was examined using an optical microscope, and the microhardness change of the joining region was determined with the HV hardness measuring device. While alpha-ferrite structure was observed in the Cu interlayered connections in the samples, multiphase structures were observed in the Al7072 and SX-Al8079 interconnected samples, and the presence of intermetallic phases was detected in both the interface and diffusion zones in the Ni interlayered samples.