A nickel-based braze alloy composition is described, including nickel, about 1 weight % to about 5 weight % boron (B); and about 1 weight % to about 20 weight % germanium (Ge). The composition is free of any silicon. Superalloy articles that contains a crack or other type of void or gap filled with the nickel-based braze alloy composition are also described, along with methods for filling such a gap. Related articles of manufacture and brazing processes to join metal components are also disclosed.