Serkan Yıldırım, Mehmet; Aydın, Kemal; Kalyon, Ali; Kaya, Yakup

This study examines the diffusion bonding behavior between 316L stainless steel and H13 tool steel, focusing on the effects of key process parameters. Specifically, the influence of bonding pressure, bonding temperature, and holding time on joint quality and mechanical performance is systematically investigated. The Taguchi optimization method was employed to determine the optimal bonding conditions, with shear strength serving as the primary performance indicator. The bonding interfaces were characterized through scanning electron microscopy to analyze microstructural evolution and diffusion behavior. Analysis of variance was conducted to assess the influence of process parameters on shear strength, identifying temperature as the most significant factor. The optimum shear strength was experimentally validated, and a confidence interval was calculated to ensure statistical reliability. The results demonstrated that higher bonding temperatures and moderate pressures led to improved diffusion at the interface, enhancing joint integrity. The findings contribute to a better understanding of the diffusion bonding process and its potential for high-performance applications in aerospace, biomedical, and tooling industries.

Aydın, Kemal; Yıldırım, Mehmet Serkan; Kaya, Yakup

This study examines the diffusion bonding of 316 L stainless steel and H13 hot work tool steel, aiming to optimize process parameters and assess the resulting microstructural and mechanical properties. Both materials were bonded at varying temperatures (700, 750, and 850 °C) and times (15, 30, and 60 min). The joints are analyzed using scanning electron microscopy (SEM), energy-dispersive spectroscopy, and X-ray diffraction (XRD) to evaluate interfacial morphology, chemical composition, and phase formation. Microhardness measurements indicate an increase in hardness from the 316 L side to the H13 side, suggesting intermetallic phase formation. Shear strength tests show the highest strength at 850 °C for 30 min, with longer times leading to strength reduction due to brittle intermetallic compounds. SEM analysis reveals improved bonding interfaces with fewer voids at higher temperatures and longer times, but the Kirkendall effect causes void formation, negatively impacting mechanical properties. XRD confirms α-Fe and γ-Ni phases, with Fe3C forming at 850 °C for 60 min. This study underscores the importance of process parameters in optimizing joint properties and minimizing brittle phase formation, providing insights for industrial applications requiring robust and corrosion-resistant joints.

Hıdıroglu, Mehtap; Aydın, Kemal; Kahraman, Nizamettin

During resistance spot welding (RSW), the thermal cycles that occur cause microstructural differentiations in the heat-affected zones of martensitic steels, leading to internal stresses. In this context, a new and innovative methodology has been developed to minimize the adverse effects of heterogeneous hardness changes in the welding area on joint durability. This methodology utilizes a unique prototype setup based on the regional rapid cooling (RRC) process, which is integrated into the welding machine and operates in synchronization with the machine during the process. Through this setup, the aim is to effectively control the microstructure and hardness values in the welding area. This innovative approach presents potential improvements in the field of welding technology by aiming to optimize material performance during the welding process. According to microstructure results, the RRC process has narrowed the heat-affected zone to 1.27 mm, increased the hardness values by 9.2%, showed a 3% increase in tensile-shear strength, a 9% increase in cross-tension strength, and based on fatigue strength results, no fractures occurred in all specimens subjected to a force of 0.3 kN.