Fatigue of Electroformed Nickel
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A 2–3 mm nickel mould, manufactured solely by electroforming, showed early cracking under thermal load cycles. Possible causes were attributed to material, design, or service deficiencies. The root cause of early fracture has been investigated thoroughly and is reported here. Monotonic and cyclic properties of electroformed nickel have been obtained at room and elevated temperature. Fatigue mechanisms were identified and compared to pure nickel. Finite element modeling of the mould under thermal cycles enabled the study of material, design, and in-service applications of the mould. It was found that over constraining the mould, while it was in service, caused excessive thermal stresses which accelerated crack initiation and propagation. Remedies to avoid failure are proposed.
KeywordsElectroformed nickel Thermal cycle Fatigue failure Thermal stress
The authors acknowledge the help of Dr. S. Winkler with the microstructure studies.
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