A New Surface Engineering Approach for Fatigue-Resistant AM Microlattices
Abstract
This work proposes to lay the basic scientific foundation for a new method to mitigate the rough surfaces inherent to additively manufactured (AM) metal parts. AM can produce unprecedented geometries, such as microlattices with significant weight savings. However, rough surfaces limit their fatigue performance, and current surface treatment options are insufficient. For example, line-of-sight techniques (e.g., shot blasting) do not address interior surfaces of complex shapes, and liquid-based approaches (e.g., etching) involve nonuniform material removal that jeopardizes fatigue predictability and performance of thin features, such as the ligaments inherent to microlattices. Thus, there is a need for advanced surface treatment options. Complex AM parts could be treated via activated surface remelting and smoothening during heat treatment. Specifically, to enhance surface remelting/densification during heat treatment, parts can first be conformally coated with a thin film to accelerate local surface diffusion and remelting activity during heat treatment. The metallurgical mechanisms of eutectic reactions inform specific compositions of coatings to target preferential surface remelting: just as salt lowers the freezing point of water, certain compositions lower the melting point of metals. This work will leverage a unique combination of chemistry, materials science, and mechanics of materials to build the basic scientific foundation for this new class of chemically accelerated surface treatment. To do so, process-structure-property-performance relationships will be established. Specifically, with an emphasis on AM Ti-6Al-4V microlattices, this work will characterize the changes in surface roughness, microstructure, and residual stress. In tandem, it will measure the resulting fatigue performance of the microlattices with and without surface treatment, and gain insights on the mechanisms of fatigue performance via crystal plasticity modeling. Throughout the investigation, a unified understanding will be sought for the processstructure- property-performance relationships for the effects of the surface treatment on AM Ti- 6Al-4V microlattices.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 21, 2022
- Source ID
- FA95502110212XX0
Entities
People
- William Lepage
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Tulsa