| Abstract: |
Salt spray test ranking is performed on plate samples high velocity oxy-fuel (HVOF) and high velocity air-fuel (HVAF) sprayed by using Fe-based powder alloys. There Fe-based powder alloys are used, all three are in fact high-alloyed steels, FeSP529, FeSP586 and 6AB. FeSP529 has austenitic-ferritic matrix and hard phase constituents are borides and carbides. FeSP586 has austenitic matrix with mainly carbides and some borides, while 6AB has ferritic-austenitic matrix with borides and carbides. As a reference, electrolytic hard chrome (EHC) plated steel samples are used. The sprayed samples are tested as spray/ground but also as surface densified by using mild shot peening. Aim with the shot peening is to close the surface pores but not to make any large overall impact on mechanical properties of the sprayed coatings. Residual stress measurements by X-ray diffraction are performed to prove this. The salt spray testing ranking, chosen for corrosion and coating performance ranking in this investigation, is otherwise a subject of numerous discussions because of its benefits and drawbacks. Just for this investigation, the salt spray testing is beneficial since it shows how coatings made of the three Fe-based powders with and without surface pore closing resists to exposition to highly aggressive medium within a test chamber. The testing itself is performed following ASTM B117 / ISO 9277 standards. The test results show benefits in corrosion protection of sprayed test samples by use of HVAF- vs. HVOF spraying and mild shot peening.
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