Journal of Welding Science

In this study, gas-tungsten arc welding was used for the cladding of two high entropy alloys of AlCoCrFeNi (Al1) and Al0.7CoCrFeNi (Al0.7) onto plain carbon steel plates. The welding process was carried out at a welding current of 180 A and a welding speed of 1.4 mm/s. The microstructures, craking behavior, phase composition, and hardness of the clads were characterized using various methods, such as optical microscopy (OM), field emission scanning electron microscopy (FESEM), X-ray diffractometry (XRD) analysis, and microhardness measurements. The results indicated that the Al1 clad had a petal-like structure of the BCC and Cr-rich phases. Both intergranular and transgranular cracks were identified in the Al1 alloy, which were recognized to be solidification cracks. Thermal stress and brittleness of the BCC phase promote cracking of the Al1. On the other hand, in the Al0.7 alloy, in addition to the BCC phase, a new FCC phase was  formed with various Widmanstatten and dendritic morphologies in the clad microstructure and the Cr-rich phase was not observed. Furthermore, in this alloy with lower Al content, a crack-free clad was obtained. The crack prevention in the Al0.7 alloy was attributed to a combination of factors, including a decrease in the solidification range, formation of the FCC phase, and reduction in hardness.

High entropy alloys are especially suitable for use as filler metals in brazing due to their excellent properties. in the present study, three powders with the composition of CoxCrxCuxFexMnxNix (X atomic percentage of the element) were designed using the criteria of these alloys as well as jmatpro software. in the next step, using mechanical alloying, filler nano powder was synthesized and characterized by X-RAY analysis (XRD) test and the effect of filler composition on the thermal behavior of the alloy was studied. then the filler was used in Inconel 600 super alloy brazing, the single-phase solidification behavior and the absence of boron and silicon in the high entropy filler led to the creation of a continuous microstructure without eutectic components or brittle phases in the brazing interface. thus, the shear strength test was performed and 545 MPa  was the highest shear strength obtained among the three filler compounds. in brazing conventional filler metal, incomplete isothermal solidification and subsequent thermal solidification of the residual liquid results in large grains of chromium-rich boride phase distributed throughout the microstructure. not using compounds that lower the melting point in the filler for the purpose of joining the nickel-based superalloy is considered an important step in reducing the subsequent brazing processes.