Correlation between special bud-shaped area and molten pool flow in laser cladding high-entropy alloy on TC4 surface

Compared with the single principal component composition of traditional alloy materials, multi-principal high -entropy alloys (HEAs) tend to cause non-uniform distribution of coating elements. In this paper, an experimental study of laser cladding of HEA coating on the surface of TC4 is carried out. In observing the morphology of the cladding layer, it is found that there are special bud-like areas where Ti element accumulate abnormally at the bottom of the cladding layer. Because it has apparent traces of molten pool agitation, it is inferred that its cause is closely related to the flow of the molten pool. The mechanism of the non-uniform distribution of elements in the laser cladding layer of HEA was studied from the perspective of molten pool flow. From the cross-section and the longitudinal-section of the molten pool, the influence of the molten pool flow on the Ti element's abnormal accumulation in the special bud-shaped area is explored. It was revealed that, a Marangoni circulation is formed at the bottom of the melt pool during laser cladding, under which the element Ti is stirred into the melting pool due to its low melting point, creating a large accumulation of elements.