TWI Industrial Member Report Summary 343/1987
By I A Bucklow
Oxide-dispersion-strengthened (ODS) alloys develop their creep resistance from a combination of a dispersion of fine oxide particles plus a massive and elongated grain size. They cannot be fusion welded without local destruction of the dispersion and interruption of the grain structure, but brazing offers the possibility of a compromise whereby joints can be made in which the degradation of high temperature properties is still within acceptable limits. The most promising condition for joining these alloys is in the fine-grained form (i.e. before recrystallisation to the massive form) with the object of obliterating the joint line by subsequent epitaxial grain growth. Two Ni ODs alloys were joined by brazing alloys containing B and Si in the form of foils or sputtered coatings, and also by brazes without B but with an enhanced Si content as the melting point depressant. Joints were examined metallographically for the presence of porosity, agglomerations of dispersoid, second-phase particles, and effects upon the parent metal microstructure. Techniques for making sputtered braze coatings of different compositions were explored.