Flux compositions adapted for use in laser welding, repair and additive manufacturing applications. Flux compositions contain 5 to 60 percent by weight of an optically transmissive constituent, 10 to 70 percent by weight of a viscosity/fluidity enhancer, 0 to 40 percent by weight of a shielding agent, 5 to 30 percent by weight of a scavenging agent, and 0 to 7 percent by weight of a vectoring agent, in which the percentages are relative to a total weight of the flux composition. Also disclosed are processes involving melting of a superalloy material in the presence of a disclosed flux composition to form a melt pool covered by a layer of molten slag, and allowing the melt pool and the molten slag to cool and solidify to form a superalloy layer covered by a layer of solid slag.