Abstract: Additive manufacturing was used to address the wide spread issue of galvanic and pitting corrosion of U.S. Army ground vehicle system (GVS) structural surfaces, and resulting reduction in the survivability of the armor. The objective of this study was to develop a permanent coating solution to supplement the existing corrosion protective coating of primer and CARC paint, and extend the lifecycle of the armor. Once a painted surface experiences wear or saturation, corrosion begins to assault the exposed armor surface. Once a pit reaches a certain depth, the section of the hull plating may require complete replacement of the full plate section. Such replacements can range in cost from $5k to $50k, depending on the location to be replaced. The U.S. Army – Ground Vehicle System Center’s (GVSC) Materials Characterization and Failure Analysis (M-CFA) team conducted a preliminary study to begin this project in FY18 by producing twenty-five permanent, 0.1 inch layer, additively manufactured (AM) coated coupons of deposited Stellite 6 cobalt alloy on MIL-STD-46100 High Hard (HH) armor steel blocks using an un-optimized set of parameters. Optimization processes takes a considerable amount of time, and a proof of concept was needed to justify that endeavor. These coupons were subjected to a twenty-four week study in accelerated corrosive conditions of a fog spray chamber alongside twenty-five primer-CARC coated coupons and twenty-five uncoated coupons from additional HH steel armor blocks. The resulting study showed no signs of pitting corrosion in the surface of the AM coated coupons, and minimal galvanic corrosion at the interface with the AM coating. During the study, the coated coupons demonstrated double the lifespan of the primer-CARC protection currently used, and may have exceeded that length if it were not for the conclusion of the study at 24 weeks. The study also demonstrated that the coating had a similar in hardness (50-53 HRC) when compared to the HH steel (49-54 HRC). One drawback from the use of an unrefined deposition process was a reduction in hardness (37-40 HRC) in the thin 0.02 inch heat affect zone (HAZ). Some porosity was also identified in the deposition itself that would require minimization for application. With the completion of the preliminary study, focus shall be carried forward to optimize the deposition process for application use.
Authors: Ian J. Toppler, Daniel C. Schleh, and Claudio Gutierrez Romero
Keywords: Direct Energy Deposition, Corrosion Prevention, Armor, Steel, Additive Manufacturing