This article emphasizes that as global competition for materials strains the supply chain, companies must know where a shortage can hurt and then plan around it. Advancements in material science are required to design materials that minimize the use of elements that are not sustainable, without losing the properties that enable product integrity. The article also highlights that elements that are determined to be high both in impact to the company and in supply and price risk require a plan either to stabilize their supply or to minimize their usage. The article also presents several examples that demonstrate the intelligent application of material science in product design. As competition for the world’s resources increases in the future, it is critical for material users to determine what changes in design and materials will allow for continued growth. This starts with an assessment of where the risks are, which is followed by a response that encompasses sourcing, manufacturing, and engineering.
Abstract.Compressive hold-time low-cycle fatigue is one of the important damage modes in Ni-based superalloy hot-gas path components. In strain controlled LCF, the compressive hold typically degrades fatigue life significantly due to creep relaxation and the resultant generation of tensile stress upon returning to zero strain. Crack initiation typically occurs on the surface, and therefore, the cracks are covered with layers of oxides. Recent finite element modeling based on experimental observations has indicated that the in-plane compressive stress in the alumina layer formed on the surface of the bond coat assists rumpling and, eventually, leads to initiation of cracks. The stress in the oxide layer continues to assist crack extension by pushing the alumina layer along the crack front during the compressive hold. In-situ measurements of the growth strains of alumina were performed using high energy synchrotron X-rays at Argonne National Lab. Specimens of single-crystal superalloys with and without aluminide coatings were statically pre-oxidized to form a layer of alumina at 1093 and 982• C. For the in-situ synchrotron measurements, the specimens were heated up to the pre-oxidation temperatures with a heater. The alumina layers on both bare and coated specimens show compressive in-plane strains at both temperatures. The oxide strains on the superalloys showed dependency on temperature; on the other hand, the oxide strains in the aluminide coatings were insensitive to temperature. The magnitude of the compressive strains was larger on the superalloys than the ones on the aluminide coatings.
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