Fatigue Crack Growth in Plasma-Sprayed Refractory Materials
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Fatigue crack growth in self-standing plasma-sprayed tungsten and molybdenum beams with artificially introduced notches subjected to pure bending was studied. Fatigue crack length was measured using the differential compliance method, and fatigue crack growth rate was established as a function of stress intensity factor. Crack opening under compressive stress was detected. Fractographic analysis revealed the respective crack formation mechanisms. At low crack propagation rates, the fatigue crack growth takes place by intergranular splat fracture accompanied by splat decohesion in Mo coating, eventually by void interconnection in W coating. Frequently, the crack deflected from the notch plane being attracted to stress concentrators formed by voids or favorably oriented splat interfaces. At higher values of the stress intensity factor, the intergranular cracking of splats becomes more common and the crack propagated more perpendicularly to the specimen surface.
Keywordsfatigue crack growth rate molybdenum RF induction plasma tungsten
This study was supported by the Czech Science Foundation Grant Project GAČR 14-36566G.
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