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7367 |
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Thursday, May 05, 2022, Hall G2 3:00 PM Medical Industry |
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Fatigues resistance driving factors for titanium plasma sprayed coated samples |
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PIERFRANCESCO Robotti / Lincotek Medical Trento, Italy Andrea Venturoli* / Lincotek Medical Trento, Italy Gioacchino Conoscenti/ Lincotek Medical Trento, Italia Roberto Chiesa/ Politecnico di Milano, Italy |
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Introduction: this work investigates the effects of different thermal plasma spray (TPS) processes and coatings on the fatigue resistance of a titanium alloy substrate, usually a popular combination in cementless total hip replacement. The use of a TPS coating process may reduce the fatigue resistance of the original substrate. At the same time the dimensions of the hip prostheses, and consequently their resistant cross-section, is been decreased year after year to accomplish the global trend to perform surgical operations with a minimally-invasive approach. Materials and Methods: One air-developed coating 300 µm thick (Ti-APS) and one formed in controlled atmosphere, 800 µm thick (Ti-CAPS) were considered. Initially we have isolated the influence of corundum (Al2O3) grain sizes blasting on the fatigue resistance. Subsequently, the effects of the most representative parameters of the two plasma spray processes were investigated. Rotating bending fatigue limit was determined through stair case method (ISO 12107:2003). The testing campaign involved more than one hundred samples. Metallographic analyses (thickness, porosity and roughness examination) were carried out on coatings and complemented by morphological analyses both on the primary crack surface and on the cross-sectional area of the specimens, which underwent fatigue failure. Results: the titanium substrate fatigue resistance decreased after being blasted with direct relationship with the grain size. Ti-CAPS process showed a relatively limited further deleterious influence on the fatigue resistance with respect to only sandblasted samples. By contrary a remarkable fatigue limit decreased was seen for Ti-APS coated samples against either Ti-CAPS and simply sandblasted samples. No significant further differences were noted by changing plasma spray parameters in both Ti-APS and Ti-CAPS family of samples. The experiment pointed out the critical importance of crack oxidation as one of the fatigue failure driving factor. |