Flexural Strength and Shear Strength of Silicon Carbide to Silicon Carbide Joints Fabricated by a Molybdenum Diffusion Bonding Technique

Abstract

The capability to form robust SiC‐to‐SiC joints is needed to enable the fabrication of complex SiC‐based structures. In this work, molybdenum foils are used to develop a diffusion bond with SiC during a vacuum heat treatment at 1500°C for 10 h. The bond consists of a central region of Mo2C with Mo5Si3+carbon and/or Mo5Si3C phases at the SiC interface. Flexure strength determined using a standard 4‐point flexural test method (ASTM C1161) over the temperature range from room temperature to 1100°C showed that the molybdenum foil joined SiC failed at a somewhat lower value (263–50 MPa) than similarly tested monolithic chemically vapor deposited (CVD) SiC without any bond (443–197 MPa). Differences in elastic properties and coefficient of thermal expansion between SiC and the phases produced in the molybdenum foil joint region likely result in the formation of slightly larger flaws in the SiC near the joint, which are fracture initiation sites that result in lower flexural strength values for molybdenum‐joined SiC. Shear strength results obtained using a double‐notched specimen are also compared for the joined and monolithic specimens, which provides fracture strength data that can be used for comparisons. The shear strength values for the molybdenum‐joined SiC (264–61 MPa) are found to be within the data scatter of the monolithic material (397–31 MPa). These results indicate that a molybdenum foil diffusion bonding technique can be used to produce joints that are as strong as continuous bars of monolithic SiC in shear‐type loading, but they have lower flexural strength values than monolithic SiC. However, the flexure strength values for molybdenum foil‐joined SiC are within the range of values or higher than values reported in literature for the joining of SiC using reaction forming, reaction‐bonding, polymer precursors, and niobium diffusion bonding.

Microstructure of reaction layer and its effect on the joining strength of SiC/SiC joints brazed using Ag-Cu-In-Ti alloy

“…Ti + SiC = TiC + Si (1) 5Ti + 3Si = Ti 5 Si 3 (2) With the development of interfacial reaction, SiC decomposes gradually and TiC nucleates at the However, it is different in our work from those reported results. An In-containing layer is found between SiC substrate and TiC layer.…”

“…Ceramic joining techniques provide a lower-cost and higher-reliable method to solve the problem. Different ceramic joining techniques, including adhesive, brazing, diffusion bonding, glass bonding and reaction bonding, have been developed to meet different demands [1][2][3][4][5][6]. Among these techniques, active brazing attracts great interest for its high joining strength and convenience in engineering applications.…”

Assessment of Silicon Carbide Composites for Advanced Salt-Cooled Reactors

“…[126] Also, the authors did not indicate any pretest cleaning procedure for the nickel crucible. Nishimura et al, did observe "black deposits," identified as Ni 31 Si 12 , on the surface of the silicon carbide specimens after exposures for three and ten days. The nickel silicide, Ni 31 Si 12 , was postulated as forming from a reaction between nickel and silicon carbide.…”

“…The diffusion bonding is typically facilitated by inserting thin metallic foil(s) between the joining surfaces of SiC. Metals like titanium [30] and molybdenum [31] have successfully been applied as the filler material. The TEP joining takes advantage of reduced melting temperature for particular silica-bearing oxide systems (such as yttria-alumina-silica) to develop SiC-based joint material through the solution and re-precipitation process.…”

A Study On The Metal Carbide Composite Diffusion Bonding For Mechanical Seal

“…Diffusion bonding is a promising approach for high temperature joints [11,12]. And diffusion bonding, a solid-state bonding process that allows the contact surfaces to be joined under pressure and at elevated temperatures with minimum macroscopic deformation, has been used for the bonding of almost all the metallic materials with incompatible chemical and metallurgical properties, whose bonding is not appropriate by classical welding methods [13].…”