Titanium carbonitride (Ti(C,N)) cermets have become more popular in recent research due to their mix of high hardness, high hot hardness, good ductility, chemical stability, and low densities. These mechanical properties make Ti(C,N)-cermets especially desirable as a replacement for current ‘hardmetals’, such as tungsten carbide cobalt (WCCo), as it is known that WC-Co exhibits poor mechanical behaviour at elevated temperatures. Additional interest and research has been conducted in reference to binders which enhance the cermet’s capability to retain strength at high temperatures while remaining ductile. One such binder, Ni3Al actually increases in yield strength up to a temperature of ~900°C. In this thesis, the production method utilizing melt infiltration for TiC, Ti(C0.7,N0.3), Ti(C0.5,N0.5), and Ti(C0.3,N0.7)-based cermets with Ni3Al binder contents of 20, 30 and 40 vol. % have successfully been developed and utilized. This process produced high density samples at each nitrogen content for all binder contents, excluding Ti(C0.3,N0.7). Ti(C0.3,N0.7)-Ni3Al samples at 20 and 30 vol. % suffered from poor infiltration and could not be tested. The reciprocating wear mechanisms were examined, using a ball-on-flat test, utilizing WC-Co spheres with a diameter of 6.35 mm as a counter-face, and test parameters of 20 Hz, 2 hrs., and applied loads of 20, 40, 60 and 80 N. The wear tracks were examined using optical profilometry, SEM, and EDS to determine the volumetric wear rate, and the dominant wear mechanisms. The wear volume, and wear mechanisms were compared with the effect of binder content, nitrogen content, and applied load.

<p dir="ltr">A current engineering challenge is to understand and validate material systems capable of maintaining structural viability under the elevated temperature and environmental conditions of hypersonic flight. One aspect of this challenge is the joining of multiple materials with thermal expansion mismatch, which can lead to residual stress, resulting in debits in component lifetime under in-service loading. The focus of this work is a series of studies focused on a ceramic-metal composite (WC/Cu), a zirconia coating applied to a carboncarbon (C/C) composite, and a silicide (R512E) coating applied to a Nb-based alloy (C103). Each of these material systems are candidates for elevated temperature applications in which dissimilar constituents result in residual stress in the material. Each study leveraged experimental residual strain measurements, with the primary focus on the use of synchrotron X-ray diffraction, in conjunction with representative models, and microscopy to illuminate the active mechanisms in the development and evolution of residual stress in the bulk material. The combination of experimental and modeling predictions provides a framework to inform the viability and lifing of material systems exhibiting dissimilar expansion properties.</p>