Adaptive Additively Manufactured High-Performance Thermal Coatings

Abstract

Additive manufacturing techniques have shown promising developments over the past few decades, with their technology continuously improving. As such, other industries such as coating manufacturing can benefit from these new technologies. The research in this dissertation introduces a new additive thermal coating technique which combines state-of-the-art additive manufacturing techniques with state-of-the-art additive thermal coating techniques. The designed and developed system is titled flash heating, and this system utilizes a localized and controllable thermal plasma heat source to fabricate coatings in an additive manufacturing-like process. Substrates to be coated are placed in a powder bed, a layer of powder of controllable thickness is placed on the surface, and the heat is subsequently applied, creating single-layer or multilayer coatings of controllable thicknesses ranging from 50 µm up to greater than 1 mm. Heat transfer analysis was performed on this process through numerical simulations, which showed the technique could fabricate thick, high melting point coatings without significantly influencing the substrate in terms of heat treatment. As a result, research showed that this technique could fabricate a variety of coatings including Ni-SiC coatings with much higher SiC content than is typically possible with state-of-the-art coating techniques. This system of coatings showed improved wear performance due to increased hardness from the high SiC content. Additionally, the corrosion performance of Ni-SiC coatings was analyzed using a statistical design known as a two-cubed (23) full factorial design. This showed that composition and plasma current during fabrication interacted with each other, requiring the two to be optimized simultaneously. Meanwhile, gas flow rate during fabrication was shown to influence corrosion independently, and as such, optimization showed that a flow rate of 12-14 cfh resulted in minimization in the corrosion rate. This research reveals the feasibility of an additive thermal coating technique as a replacement for conventional coating techniques for high-performance coatings.