Defect-tolerant characteristics of laser sintered CoCrMo alloy ensured by strong structural hierarchies
(English)Manuscript (preprint) (Other academic)
Laser sintering of a CoCrMo alloy have been found to introduce intergrown structural features on several length scales from nano- to macro-levels, i.e. structural hierarchies. The quenching of the small laser formed melting pool, when the laser focus spot moves away, will preserve high temperature phases or microstructures. A micron-sized cellular microstructure will form with Mo being enriched in a nanometer thin zone at the cell boundaries and carbide formation is suppressed. Clusters of elongated cells (crystallites) join along one common crystal structure direction forming larger up to 100 µm bundles and these grow in different intercrossing directions in the microstructure. The interlocked framework prohibits mechanical creep or deformation by sliding along weak structure planes and consumes the energy of a propagating crack. A macro-scale “weld line” structure can be formed in 3-dimensions by the bottom-up approach; the sintering of layer by layer with a tailored scan track. The sintered alloy contained three types of defects comprising micron sized voids or cracks occurring at the cluster boundaries and larger cracks at the “weld line” boundaries. Unexpected good mechanical properties are achieved despite the observed microstructural defects and the laser sintered Co-Cr-Mo alloy seems very defect tolerant. This positive effect is ascribed to the strong structural hierarchies found in the laser sintered CoCrMo alloy.
laser sintereing, Alloy, mechanical property, microstrcture
IdentifiersURN: urn:nbn:se:su:diva-101095OAI: oai:DiVA.org:su-101095DiVA: diva2:698914