nickel base superalloys , including in some embodiments 5 % to 7 % fe , which were previously developed and used for their corrosion resistance , also possess favorable characteristics for use as a braze filler in repair or joining of superalloy substrates , such as those used to form turbine engine blades and vanes , heat exchangers , vessels , and piping . in particular , such corrosion - resistant nickel base superalloys have favorable characteristics for wide - gap brazing of gaps greater than one millimeter in superalloy substrates that preserves favorable material properties throughout the braze region in the substrate .