High‐performance infrared emissivity of micro‐arc oxidation coatings formed on titanium alloy for aerospace applications

Abstract

Aerospace vehicles are subjected to high temperatures because of surrounding aerodynamic drag and the formation of large temperature gradients across the external structural parts of their airframe. To protect the vehicles, high‐infrared emissivity coatings that can radiate a large amount of heat into outer space are in demand. In this work, we describe the development and characterization of high emissivity ceramic coatings formed on a TC4 alloy surface by micro‐arc oxidation. We evaluate, in particular, the influence of NiSO4 concentration on current‐time response, the thickness, surface roughness, morphologies, bonding strength, and emissivity of these coatings. The results indicate that by increasing the NiSO4 concentration in electrolytes, the thickness and surface roughness of the coatings increase. The bonding strength becomes smaller with increasing concentration of NiSO4, but is still maintains a value higher 30 MPa. The coatings possess good thermal shock resistance after being subjected to severe thermal shocks for 50 cycles, and no peeling of the coating is observed. A higher concentration of NiSO4 in electrolytes also leads to an increasing percentage of the nickel components in the coating to form a NiO phase, which enhances the emissivity of the coatings in the wavelength range of 3‐8 μm.

Formation Mechanism and Biological Properties of Different Structured HA/TiO2 Coatings on Titanium Prepared by Micro-Arc Oxidation

“…Ti 4+ + O 2 − → TiO 2 [8] During MAO process, OH − , PO 4 3− and HPO 4 2− groups in electrolyte move toward anode by electrophoresis under the strong electric field, and Ca 2+ ions are transferred to anode mainly by diffusion and convection. All the groups are solidified on anode surface along with the melted material sprayed out from the discharge channels.…”

“…By MAO, coatings with different composition and microstructures could be obtained by controlling the applied parameters such as voltage, anodizing electrolyte, temperature, and frequency. [8][9][10] Besides, it has been reported that MAO can enhance the adhesion force of the coating to the substrate due to the existence of the rough interfacial layer of TiO 2 , and the binding force can reach as high as 26.5 N detected by the scratch test. 11 When implanted in the body, the first step that will happen is cells attachment to the implant.…”

Laser Based Additive Manufacturing Technology for Fabrication of Titanium Aluminide-Based Composites in Aerospace Component Applications

“…One of the titanium alloys that are ideal for aerospace applications is the β-Ti alloy because it has a combined property of high strength and lightweight [48]. Titanium alloys have proven to be extremely attractive and important materials in aerospace applications because of excellent combinations of outstanding corrosion and mechanical properties [39,47,49,50]. Recently, there has been increased interests in the development of additively manufactured titanium (and their alloys) parts in industries.…”

The Influence of Heat Treatment Temperature on Microstructures and Mechanical Properties of Titanium Alloy Fabricated by Laser Melting Deposition

“…Titanium alloys are widely used in aerospace and biomedical fields due to their high tensile strength and fatigue strength, low elastic modulus and density, high temperature performance, and good corrosion resistance [1][2][3]. As a medium strength α + β titanium alloy, Ti-6Al-4V is widely used in fields of aircrafts and aeroengines [4,5]. However, it is difficult to process due to the high melting point, high melting activity, and high deformation resistance of Ti-6Al-4V [6,7].…”