Resistance to fracture of thermal sprayed ceramic coatings
- Univ. of British Columbia, Vancouver, British Columbia (Canada)
The fracture process zone due to bridging and frictional interactions of crack interfaces is expected to be a major toughening source for sintered ceramics. Analysis of microstructures, fracture surfaces and observations of crack paths in thermal sprayed ceramics suggests, that crack interface bridging could have a major contribution to toughening also of these materials. The frictional interactions of crack interfaces effectively results in shielding of the crack tip from externally applied stress. The paper reports the first attempt to quantify the bridging zone in thermal sprayed ceramics. The fracture process zone has been characterized in terms of the bridging (or shielding) stress profile, as a function of the crack opening displacement, for thermally sprayed WC/Co (12wt% and 17wt%) and Al{sub 2}O{sub 3}/TiO{sub 2} (3wt% and 13wt%). The incremental fracture resistance, due to crack interface bridging and frictional dissipation of fracture energy, is estimated to be at the level of {approximately}20 J/m{sup 2} for brittle composites (Al{sub 2}O{sub 3}/3wt% TiO{sub 2}; Al{sub 2}O{sub 3}/13wt% TiO{sub 2} and WC/12wt% Co), and {approximately}55 J/m{sup 2} for WC/17wt% Co. The shielding stress profile appears to be characteristic for the material and sensitive to the process parameters. The maximum shielding stress in thermal sprayed ceramics under consideration did not exceed 10 MPa, the value being characteristic of heavily microcracked geomaterials or cements. It is tentatively concluded, that the data on the bridging stress profile can be utilized for maximization of the resistance to fracture and thermal shock of thermal sprayed ceramics.
- OSTI ID:
- 160517
- Report Number(s):
- CONF-940684-; ISBN 0-87170-509-5; TRN: 96:006049
- Resource Relation:
- Conference: 1994 national thermal spray conference, Boston, MA (United States), 20-24 Jun 1994; Other Information: PBD: 1994; Related Information: Is Part Of 1994 Thermal spray industrial applications: Proceedings; Berndt, C.C.; Sampath, S. [eds.] [State Univ. of New York at Stony Brook, NY (United States). Dept. of Materials Science and Engineering]; PB: 816 p.
- Country of Publication:
- United States
- Language:
- English
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