Dissimilar Rotary Friction Welding of Inconel 718 to F22 Using Inconel 625 Interlayer

Dissimilar metal joining has always been a challenging task because of the metallurgical incompatibility and difference in melting points of alloys being joined. Diffusion and mixing of alloying elements from dissimilar base metals at the weld often cause unwanted metallurgical changes resulting in unsuccessful welds or underperformance of the weldment. Solid-state dissimilar friction welds of Inconel 718 and F22 were prepared in this study with an Inconel 625 interlayer to address the carbon enrichment of Inconel 718 during the welding. Defect-free rotary friction welds were produced in this study. Microstructural and mechanical properties investigation of the weldments and base metals was carried out, and results were analysed. Intermixing zone was observed at the weld interface due to the softening of the metal at the interface and rotatory motion during the welding. The high temperatures and the plastic deformation of the intermixing zone and thermo-mechanically affected zone (TMAZ) resulted in the grain refinement of the weld region. The highest hardness was observed at the Inconel 718/F22 weld interface due to the plastic strain and the carbon diffusion. The tensile specimens failed in the F22 base metal for the weld prepared with and without the Inconel 625 interlayer. Inconel 718/F22 welds exhibited lower toughness values compared to the Inconel 718/F22 welds prepared with Inconel 625 interlayer.

Microstructural Control of the Interface Layer for Strength Enhancement of Dissimilar Al/Cu Joints via Ni Addition during TIG Arc Brazing

Dissimilar metal joining between Al and Cu is effective for reducing the weight and cost of electrical components. In this study, dissimilar lap joining of pure Al to pure Cu with an Al-Ni filler material was conducted using tungsten inert gas (TIG) arc brazing, and the effect of Ni on the joint strength associated with the microstructure of the intermetallic compound (IMC) layer at the dissimilar interface was examined. The addition of Ni effectively increased the interfacial strength of the joints. Regardless of the addition of Ni, the joints fractured in the thick Al2Cu layer formed at the Al/Cu interface. However, the Ni addition reduced the thickness of the IMC layer and led to the formation of Al7Cu4Ni particles in the weakest Al2Cu layer. Both the thickness reduction and reinforcing Al7Cu4Ni particle formation are thought to contribute to the increase in joint strength of the Al/Cu dissimilar interface.