Continuous Wire Electrical Explosion Spraying for Porous Coating Deposition Inside a Narrow Tube

Abstract

Heat exchange tubes require a porous inner surface to maximize their boiling performance. However, in addition to the geometric limitations of long and narrow tubes, producing porous inner surfaces remains challenging for conventional coating technologies. To prepare porous coatings on the inner surface of narrow tubes, a novel continuous wire electrical explosion spraying device was developed. The charging voltage influenced the overheat factor and expansion velocity of the aluminum wire, which simultaneously affected the size, temperature, and velocity of the explosive products deposited inside medium-carbon steel tubes. These effects ultimately impacted the flattening degree and microstructure of the deposited material. Experiments revealed that the porosity, wettability, adhesion, and rate of increase in coating surface area are all superior at a charging voltage of 12.0 kV. Thus, coatings prepared at this charging voltage can effectively improve the heat transfer of the tube. Our study also provides insights into the effects of charging voltage on the microstructure of deposited film, which may be extended to the coatings of other complex components.