Use of a cobalt based metallic-glass in joining mosi2 to stainless steel

摘要

The successful use of a cobalt-based metallic-glass in joining molybdenumdisilicide (MoSi(sub 2)) to stainless steel 316L was demonstrated. Such joints are being investigated for sensor tube applications in glass melting operations. The cobalt-based metallic-glass (METGLAS(trademark) 2714A) was found to wet the MoSi(sub 2) and stainless steel surfaces and provide high quality joints. Joining was completed at 1050 C for 60 minutes in two different ways; either by feeding excess braze into the braze gap upon heating or by constraining the MoSi(sub 2)/stainless steel assembly with an alumina (Al(sub 2)O(sub 3)) fixture during the heating cycle. These steps were necessary to ensure the production of a high quality void free joint. Post-brazing metallographic evaluations coupled with quantitative elemental analysis indicated the presence of a Co-Cr-Si ternary phase with CoSi and CoSi(sub 2) precipitates within the braze. The residual stresses in these molybdenum disilicide (MoSi(sub 2))/stainless steel 316 L joints were evaluated using X-ray diffraction and instrumented indentation techniques. These measurements revealed that significant differences are induced in the residual stresses in MoSi(sub 2) and stainless steel depending on the joining technique employed. Push-out tests were carried out on these joints to evaluate the joint strength.