Concurrent Enhancement of Fatigue Life and Corrosion Resistance via Laser Shock Peening

点击翻译按钮获取中文摘要

This research project addresses the fundamental science associated with surface deformations induced by laser shock peening (LSP), and their use to improve the stress corrosion cracking (SCC) resistance of metallic components in addition to LSP's well-known effect on fatigue life. SCC is a phenomenon where the combination of a tensile load in a corrosive environment causes premature failure. This failure is often sudden, catastrophic and occurs at loading levels far below a material's yield strength, making it difficult to predict. Depending on the material and environment, SCC can occur through different mechanisms, thus there is a need to identify mitigation approaches. Shockwaves generated on the surface using LSP impart compressive residual stresses, without thermal effects, and have traditionally been used to improve the material's fatigue life. They also induce other changes at the microstructural level, which may help mitigate SCC concurrently. Improving material performance will enhance the capability of existing technologies, potentially by allowing them to operate at higher tensile loads for longer times. In addition, the surface treatment methodology can be applied to different materials and geometric configurations, thus providing effective solutions for many industries ranging from nuclear reactors to oil production to medical devices. As such, the research has significant breadth and directly and positively impacts economic welfare and national security. By networking with minority groups such as National Society of Black Engineers, underrepresented students will be recruited. High school students and STEM teachers from neighborhood schools in northern Manhattan and the Bronx will be engaged in an innovative combination of "reach out" and "let in" activities.This project will set forth the mechanisms that allow deformation processes to have stress corrosion cracking (SCC) mitigation benefits. Fundamental understanding of the interaction between the shockwave-induced microstructural changes and the SCC pathways will be developed. Hydrogen has been identified as a major component driving SCC, and thus entry of hydrogen into the surface and propagation of absorbed hydrogen within the lattice will be better understood. Movement of mobile dislocations can contribute to crack propagation. Both of these components will be influenced by dislocation cell structures formed during shockwave processing. In addition, the electrochemical effects of the deformation process on SCC and their mitigation will be studies in a fundamental approach. Finally the project will perform scientific investigation into the balance between LSP's effect on fatigue life and SCC resistance.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.