Abstract

A cast iron repair process that restores above 80% of the original tensile strength without thermal pre-conditioning is presented. Cast iron, an integral alloy to transportation and agricultural sectors, is a difficult alloy to repair owing to the presence of discrete graphite flakes and the tendency to form brittle iron-carbide phases and porosity. Preheating and post-process annealing assist in preventing premature fracturing but are economically and environmentally impractical for large castings. Thus, methods that circumvent these limitations while avoiding defect formation are crucial. Laser-based directed energy deposition (DED) offers a highly controllable method of remanufacturing cast iron and high carbon steel components. Lower thermal input and dilution in DED contribute to less porosity and smaller thermal gradients compared to welding processes. The result is that, under a narrow range of process parameters (laser power, scanning speed, etc.), defects can be avoided. This study expands the DED processing window of cast iron and steel through ancillary processing strategies, namely, varying filler material composition, wire feeding, and melt pool vibration. Using nickel-based filler material, 82% of the cast iron ultimate tensile strength may be restored without auxiliary preheating and annealing cycles. In-situ high speed imaging complements this work by quantifying process stability under various processing conditions (laser power, scanning speed, etc.). Using low thermal input conditions, the repair strength may be maximized while reducing gas generation and escapement during melting. Wire feeding was also found to maximize process stability by reducing the amount of graphite that was vaporized or oxidized during laser exposure. A novel method of localized ultrasonic melt pool vibration was shown to refine the microstructure in deposited stainless steel 316L and promote equiaxed grain formation. The use of these technologies enhances the robustness of DED techniques, expanding the application scope and lowering the cost to entry for iron and steel repair. As society aims toward technologies that reduce greenhouse gas emissions and energy consumption, this work provides a foundation for laser-based DED restoration of cast iron and dissimilar material structures.

Library of Congress Subject Headings

Cast iron--Maintenance and repair; Additive manufacturing; Pulsed laser deposition

Publication Date

7-3-2023

Document Type

Dissertation

Student Type

Graduate

Degree Name

Mechanical and Industrial Engineering (Ph.D)

Department, Program, or Center

Mechanical Engineering (KGCOE)

Advisor

Iris V. Rivero

Advisor/Committee Member

Denis R. Cormier

Advisor/Committee Member

Yunbo Zhang

Comments

This dissertation has been embargoed. The full-text will be available on or around 7/31/2024.

Campus

RIT – Main Campus

Plan Codes

MIE-PHD

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Available for download on Tuesday, July 30, 2024

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