Electromechanical Behavior and Environmental Resistance of Laser-Fabricated Oxides on Stainless Steel

Samantha Lawrence, Purdue University

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Concentrated, nanosecond-pulsed laser exposure of oxidizing metals in ambient atmosphere produces metastable dielectric oxide coatings with characteristic colors. These oxide films, when placed on welded or sealed systems, can act as passive indicators of tampering for components in critical energy applications. The combined properties of the oxide-substrate system control the coupled electromechanical behavior and environmental stability of the oxide. Characterization of oxides grown on 304L stainless steel using electron microscopy and X-ray diffraction indicated that films consist of multiple crystalline phases with misfit strains leading to through-thickness cracking. Nanoindentation was used to assess the mechanical behavior, including fracture and residual stresses during growth and resistance to wear. Immersion testing in corrosive environments confirmed both that observed oxide cracking is through-thickness and that the substrate is modified during laser processing. Finally, electrically conducting nanoindentation indicated that defect structure and electromechanical response vary with processing conditions and environmental exposure. Combining techniques provides a unique approach for defining the coupling of electro- and chemo-mechanical behavior, and thus the applicability, of laser-fabricated oxide films grown on engineering alloys in harsh conditions.

Abstract Author(s): Samantha K. Lawrence, David P. Adams, David F. Bahr, Neville R. Moody