Use of a Cobalt-Based Metallic Glass for Joining MoSi₂ to Stainless Steel

Abstract

The successful use of a cobalt-based metallic-glass in joining molybdenum disilicide (MoSi 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 TM 2714A) was found to wet the MoSi 2 and stainless steel surfaces and provide high quality joints. Joining was completed at 1050 o C for 60 minutes in two different ways; either by feeding excess braze into the braze gap upon heating or by constraining the MoSi 2 /stainless steel assembly with an alumina (Al 2 O 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 2 precipitates within the braze. The residual stresses in these molybdenum disilicide (MoSi 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 2 and stainless steel depending on the joining technique employed. Push-out tests were carried out on these joints to evaluate the joint strength.