Material - Brazing Alloys - Titanium Alloy Joining Wetability and Erosion Characteristics

Abstract

Abstract : Brazing tests involving commercially pure titanium honeycomb core joined to various titanium alloy face plates (commercially pure, Ti 5Al 2-1/2 Sn, Ti 6Al-4V, nickel plated Ti 5Al-2-1/2 Sn, nickel plated Ti 6Al-4V, and nickel plated Ti 8Mn) with an eutectic composition silver copper brazing alloy (Handy and Harman Co., BT alloy, 72% silver - 28% copper). Heating the BT alloy to its flow point (1435 F) in contact with the various titanium alloys and in the presence of an inert atmosphere showed that lithium additions to the brazing alloy and nickled plating on the titanium alloys was not necessary to achieve good flows and wetability. This was attributed to the ability of titanium to absorb its own oxide at temperatures above 1300 F, a situation in which titanium alloys appear to possess a certain self-cleaning capability in the presence of inert atmosphere and moderate oxide coatings. The erosion of titanium, especially the 0.002 in. thick honeycomb core material was attributed to its solution in the brazing alloy, a character istic which requires use of minimum brazing time to obtain satisfactory joints.