Additive manufacturing of Ti-6Al-4V/V-interlayer/17-PH steel functionally graded material using angular and spheroidal V powders

The applications of V as an interlayer in functionally graded materials (FGMs) fail prematurely because of its angular shape. In this study, a radiofrequency thermal plasma process was employed to change the shape of V powder from angular to spheroidal. The angular and spheroidal V powders were then used to fabricate two FGMs, namely, Ti-6Al-4V/angular V/17-PH and Ti-6Al-4V/spherical V/17-PH. Unlike the angular V powder, the spherical V powder created a sound joint interface with a uniform layer and no cracks or delamination. The spheroidized V interlayer was thicker than the angular V interlayer. Unlike the spheroidized V interlayer, the angular V interface exhibited microcracks surrounded by sigma phases. Moreover, Ti-6Al-4V/spherical V/17-PH exhibited superior mechanical properties. The high flowability associated with the fine spherical powders of Ti-6Al-4V/spherical V/17-PH significantly enhanced the efficiency of additive manufacturing and improved the microstructure and mechanical properties of the deposited joint.