Structural Restoration Viability Using Cold Spray Technology
Saravanan R Arunachalam and Scott A Fawaz
3290 Hamal Cir, Monument, CO 80132, USA
Abstract: Cold Spray (CS) Technology has proved to be an effective geometry restoration technology to repair/restore/enhance the airworthiness of aging aircraft. The paper provides a brief review of the literature in the area of CS activity followed by results from our studies providing evidence that CS is a viable technology for structural repair applications. The airworthiness community is concerned about the load carrying capability of the coating and understanding the type of bonding between the CS coating and substrate. The primary aim of this paper is to shed light on the current research and technological development in CS and some critical experimental results from our studies. To study the structural behaviour of the CS, Al 7075 –T651 plate was coated with 7075 Al atomized powder and the static and fatigue performance were studied. Test specimens simulated repair of a 20% thickness loss by milling Al 7075 master plates (9.1” x 8.75”) followed by depositing Al 7075 powder using the CS process. During monotonic load tests, the strain was measured on both the coating and substrate. Strain measurement on the coating shows load transfer until ~90% of the ultimate tensile strength of the substrate material. Fractographic evidence shows dimple failure in both the coating and at the interface. Similarly, the fracture surface of the fatigue coupons shows evidence of striations in the coating and smooth transition between coating and substrate. These observations strongly suggest that the CS bonding at the interface is truly by metallurgical bonding. Test results are validated and supported by detailed fractographic studies.