Properties of High Velocity Arc Sprayed Coatings
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High Velocity Air Fuel Electric arc spraying (HVAF Arc) is a thermal spraying technology that is quite similar to electric arc spraying. The difference between these two types of spraying equipment is that whereas the electric arc spraying technology uses compressed air as the atomizing gas, HVAF Arc uses the combustion products of propane and air. As HVAF Arc has not been widely researched, information about how the apparatus actually functions and what kind of effect changing its spraying parameters has, was desired. This thesis consists of theoretical and experimental parts. In the literature review, thermal spraying technologies and the microstructure of thermally sprayed coatings is discussed briefly. Electric arc spraying, High velocity arc spraying (HVAS) and HVAF Arc especially are presented in more detail. In the experimental part, results from tests made to HVAF Arc specimens that have been strayed with different spraying parameters are presented. These tests include composition and thickness analyses, surface roughness tests, Vickers hardness tests, an erosion and a corrosion test. According to the results, HVAF Arc coatings have fine microstructure, with low porosity, but are quite heavily oxidized. They are typically more oxidized than coatings made without using propane as a process gas, though the HVAF Arc coatings have lower surface roughness, less pores and slightly higher hardness, due to the amount of oxides in the coating. Typically, by changing spraying parameters the coating qualities of HVAF Arc do not change much.