高速フレーム溶射およびプラズマ溶射したアルミナ被覆ステンレス鋼の疲労挙動

概要

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Rotating bending fatigue tests have been conducted in laboratory air using type 403 stainless steel with Al_2O_3 coating thermally sprayed by high velocity oxygen fuel (HVOF) process. Two different coating thicknesses of 150μm and 300μm were evaluated. The test results were compared with those of specimens with atmospheric plasma sprayed (APS) ceramics coating, and the effects of coating thickness and spraying process on fatigue behaviour were investigated. The fatigue strengths of the coated specimens were lower than those of the substrate, and decreased with increasing coating thickness when the stress was calculated including the coating thickness in the specimen diameter. On the other hand, the fatigue strengths of the coated specimens were improved compared with the substrate, when the stress was calculated from the nominal diameter of the uncoated specimen. Exceptionally, the HVOF sprayed specimens whose coating thickness was 300μm exhibited significantly lower fatigue strengths than the substrate. The dependence of fatigue strength on coating thickness and spraying process was discussed based on the observation of crack initiation in the substrate and cracking in the coatings.
2009-01-25