The evolution of advanced ceramic materials over the past two decades has not been matched by improvements in ceramic joining science and technology, particularly for high temperature applications. Of the techniques being evaluated for joining ceramics, brazing has been found to be the simplest and most promising method of fabricating both ceramic/ceramic and ceramic/metal joints. A key factor in ceramic brazing is wetting of the ceramic by the filler metal. / This study deals with the application of brazing for the fabrication of $ rm Si sb3N sb4/Si sb3N sb4$ and $ rm Si sb3N sb4/Mo$ joints using Ni-Cr-Si brazing alloys based on AWS BNi-5 (Ni-18Cr-19Si atom%). Thermodynamic calculations were performed to predict wetting at $ rm Si sb3N sb4$/Ni-Cr-Si alloys interfaces. By using some simplifying assumptions and suitable scaling of the reaction, the model predicted that Ni-Cr-Si alloys with Ni/Cr = 3.5 and X$ sb{ rm Si}$ $<$ 0.25 would react chemically with and wet $ rm Si sb3N sb4$. Good agreement was found between the theoretical calculations and experimental results. / Brazing experiments were carried out to study the joinability of $ rm Si sb3N sb4$ with various Ni-Cr-Si filler metals which had already shown good wetting characteristics on $ rm Si sb3N sb4$. The $ rm Si sb3N sb4/Si sb3N sb4$ joints formed with a 10 atom% Si brazing alloy exhibited the highest strength ($ approx$120 MPa) which was mainly due to the presence of a CrN reaction layer at the ceramic/filler metal interface. The high temperature four-point bend strengths of $ rm Si sb3N sb4/Si sb3N sb4$ joints were markedly higher than the room temperature values. A high strength of about 220 MPa was achieved when the joints were tested at 900$ sp circ$C. / From the results of the $ rm Si sb3N sb4/Mo$ joining experiments it was found that the joint quality and microstructure were strongly influenced by the composition of the filler metal and such brazing variables as time and temperature. Of all the $ rm Si sb3N sb4$/Mo joints, those made with the S10 brazing alloy at 1300$ sp circ$C for 1 min. exhibited the highest strength of 55 MPa. / Finally, in all the cases, the shear strength of all the joints was found to be lower than their four-point bend values.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.41370 |
| Date | January 1993 |
| Creators | Hadian, Ali Mohammad |
| Contributors | Drew, R. A. L. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Mining and Metallurgical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001393744, proquestno: NN94628, Theses scanned by UMI/ProQuest. |
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