Development and Evaluation of Wide Clearance Braze Joints in Gamma Prime Alloys.

Abstract : The mechanical properties of wide-clearance brazed butt joints in ALLOY 713C are reported. The joints vary in clearance from 10 to 70 mils and are made by a two-step technique. The joint is first filled with a powdered metal which has a relatively high melting point and then a partial sintering step is performed. The joint is completed by filling the porous sinter powder with a nickel brazing alloy. Brazing filler metal powders and sinter filler metal powders were evaluated for their compatibility and brazing was improved by cleaning the base metal pieces by the fluorocarbon cleaning process (FCP). For the right filler metal combination (Rene 80 with D 15 alloy) joint tensile strengths rivalled the base metal. There is no evidence of variations in strength with widths of clearance. In slow strain rate tests such as thermal fatigue and stress rupture, the results were widely scattered. The scattering is related to a plane of pores that develops at the upper faying surface of the joint during brazing. A case is made for the probability that the mechanical properties of such joints, when of high integrity, would rival and perhaps excel those of the ALLOY 713 base metal. (Author)