Mechanical properties of joints of stainless steel and titanium brazed with silver filler material

Abstract

Joining of titanium and its alloys with stainless steel by means of welding methods and obtaining joints characterised by good operation properties constitutes nowadays a significant problem in relation to research and technology. Apart from specialised welding technologies, brazing is one of the basic methods applied for joining these material combinations having diversified physical and chemical properties. Brazing is especially recommendable in the production of systems and heat exchangers for chemical industry as well as subassemblies of nuclear reactors and aircraft engines and accessories. Similarly as in case of welded joints of stainless steel and titanium, mechanical properties of brazed joints of the aforesaid materials are connected with the occurrence of hard and brittle intermetallic phases appearing often in the form of continuous layers on braze boundaries. This work reports testing of strength properties and investigation of structures of vacuum-brazed joints of stainless chromium-nickel steel (X6CrNiTi18-10) and titanium (Grade 2) at 820–900◦C for 5–20 min by means of silver brazing filler metals grade B-Ag72Cu-780 (Ag72Cu28), B-Ag68CuSn-730/755 (Ag68Cu28Sn4), and B-Ag65CuSnNi-740/767 (Ag65Cu28Sn5Ni2). Conducted investigation of joint structures indicates brittle layers of solid solutions on the base intermetallic phase where the test pieces lost their continuity in the shear test. The test results allowed to specify the most convenient brazing parameters of the tested material system from the mechanical properties point of view. Kinetic of creation and development of brittle layers of solid solutions on the base intermetallic phases in structures of brazed joints will be presented in separate publication. This publication regards only to the results of structural test which are connected with mechanical properties of joints. K e y w o r d s: vacuum brazing, stainless steel, titanium, mechanical properties of brazed joints, brazing parameters