Diffusion bonding of Nickel to Silicon Carbide, Silicon Nitride, and Yttria Stabilized Zirconia
Open Access
- Author:
- Stutzman, Amanda
- Graduate Program:
- Materials Science and Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- August 20, 2021
- Committee Members:
- Douglas Edward Wolfe, Thesis Advisor/Co-Advisor
Jeremy Michael Schreiber, Thesis Advisor/Co-Advisor
John C Mauro, Program Head/Chair
Matthew H Lear, Committee Member - Keywords:
- dissimilar joining
nickel
silicon carbide
silicon nitride
yttria stabilized zirconia
diffusion bonding - Abstract:
- Undersea vessels face continual challenges to dive deeper and move more quickly through the water. With increasing ocean depth comes substantial increase in pressure, requiring that vessels be constructed of materials with high tolerance for compressive stress. In addition, the material must be tough to prevent fracture and failure if damage is caused, either on land or in operation. Certain ceramic materials, such as silicon carbide (SiC), silicon nitride (Si3N4), and yttria stabilized zirconia (YSZ) fit the bill, having high tolerance for compressive stress and high values of fracture toughness. However, ceramic materials can be susceptible to wear, particularly fretting wear if a component is rubbed back and forth across the surface, leading to catastrophic failure. This work explores the application of a metallic layer, in this case nickel, to these tough ceramic materials to act as a wear surface to prevent ceramic damage. Bonding of dissimilar materials, such as metals to ceramics, can be challenging due to large differences in coefficient of thermal expansion, ductility, Young's modulus, fatigue/fracture mechanics, crystal structure, and atomic bonding among others between the two materials. Processes, such as mechanical joining, adhesive/chemical joining, brazing, and hybrid joining have been successful in bonding metal to ceramic. However, challenges such as galvanic corrosion, crevice corrosion, and stress concentration limit their application. Diffusion bonding is a process that has been proven effective for the joining of metal to ceramic. However, differences in coefficient of thermal expansion still pose challenges during and after the bonding process. This work details the exploration of both traditional diffusion bonding processes and diffusion-enhanced bonding processes for the joining of metals to ceramics. The traditional approaches tested include bonding of a 99.9+$\%$ pure Ni foil to SiC, Si3N4, and YSZ disks using (1) a hot isostatic press (HIP), with or without added weight to promote interfacial contact and (2) field assisted sintering (FAST). Diffusion-enhanced bonding approaches focused on bonding the Ni to the ceramic prior to diffusion treatment, so that diffusion enhances the sealing of the interface and the bond strength rather than forms the bond. Several approaches were tested for applying the Ni to the ceramic disks, including: cold spray, electroless plating, electroplating, and electron beam physical vapor deposition (EBPVD). After the Ni was bonded to the ceramics, diffusion heat treatments were carried out in the HIP at various times and temperatures based on literature values of the diffusion coefficient for each materials combination. Post-heat treatment diffusion characteristics were analyzed by scanning electron microscopy (SEM) with energy-dispersive x-ray spectroscopy (EDS). Adhesion of heat-treated specimens was characterized by tape tests per ASTM standard D3359. Preliminary results indicate success in bonding Ni to SiC, Si3N4, and YSZ using a diffusion-enhanced approach on electroplated specimens. Diffusion of Si throughout the entire Ni layer was detected for heat-treated Ni-plated SiC substrates, forming the \delta-(Ni2Si) phase. Diffusion in plated Si3N4 and YSZ samples was less extreme, with only traces of elemental diffusion detected in these cases. Diffusion in plated Si3N4 and YSZ samples could likely be promoted through higher temperature and/or longer time heat treatments, though care must be taken to avoid any eutectic melting in either system. The benefit to coating adhesion is inconclusive due to the small, pre-cut specimens used for analysis. Adhesion testing using replicated, un-cut 1 in. buttons by either tape testing (ASTM standard D3359) or tensile testing (ASTM standard C633) would provide more conclusive results regarding the adhesion enhancement (or degradation) resulting from the diffusion process.