Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 150124

150124 - Optimizing Thermal Spray Coating Thicknesses on Varied Substrate Roughness Based on Pull-Off Tensile and Portable Adhesion Tests 

Strong adhesion between coatings and substrate is critical for ensuring the performance and reliability of coatings in various engineering applications. The thickness of metallic coatings can also significantly influence bonding performance. However, there are currently limited guidelines available regarding the optimal thickness of metallic coatings on specific rough substrates, making it challenging to achieve the best performance. This research explores the impact of substrate surface roughness and coating thickness on the interfacial bonding performance of wire arc coatings on A36 steel surfaces and Q-panels of cold-roll steel. A series of tests were performed to determine adhesion strength according to ASTM C633 and pull-off strength using a portable adhesion tester per ASTM D4541. Three different aluminum oxide grits —fine (#240), medium (#54), and coarse (#12)—were blasted to achieve the desired substrate roughness. Al-arc coatings were then sprayed on each rough surface with thicknesses of 0.2, 0.3, and 0.4 mm. Three samples were prepared and tested for each roughness and coating thickness combination to determine the mean adhesion strength, resulting in a total of 27 samples for each test. For the pull-off test, 10-inch long cylindrical samples with a 1-inch diameter were machined. Coatings were applied on the cross-section of one cylinder and an uncoated counterpart cylinder was affixed to the coating using Master Bond epoxy. An uncoated sample was also tested for comparison purposes and to check the epoxy’s strength. For the portable adhesion test, dollys (studs) were adhered perpendicularly to the Al-arc coated Q-panels (3”×6”) using a two-part instant setting epoxy. Both epoxies were cured at the recommended temperatures by their respective manufacturers. Morphologies of the loose sandblast grits, sandblasted profiles, and coatings were studied using SEM. Results revealed that thicker coatings (0.4 mm) on coarse and medium surfaces showed maximum adhesive strength and strain values. Conversely, on finer surfaces, thin coatings (0.2 mm) performed better, while thicker coatings showed the lowest adhesion strength values. The bonding strength and maximum strain of neat epoxy exceeded 90 MPa, significantly surpassing the bonding strength of any coating and surface roughness combinations. SEM images of the loose grits indicate that the medium and fine grits are sharp and angular particles, while SEM images of blasted profiles indicate rougher profiles of coarse and medium grits, which could make stronger bonds with the metallic coatings. Ultimately, this study enhances our understanding of the critical factors that impact the bonding performance of wire arc coatings, providing valuable insights into optimizing the coating process.

Presenting Author: Gul Badin North Dakota State University

Presenting Author Biography: Gul Badin is a Graduate Research Assistant at North Dakota State University (NDSU), pursuing his Ph.D. in Civil Engineering with a focus on the durability of transportation infrastructure. His research centers on the durability and bonding performance of thermal spray coatings, funded by the National Science Foundation (NSF). He is also involved in other projects funded by the Department of Defense and the Department of Transportation.

Previously, he worked as a Lecturer at Abasyn University Islamabad Campus, Pakistan, in the Civil Engineering Department. As a graduate research assistant at the University of Engineering & Technology (UET), Taxila, he worked on developing cool, non-black, and energy-efficient pavement materials (asphalt), which have been published in high-impact journals.

Authors:

Gul Badin North Dakota State University
Ying Huang North Dakota State University