Chemical milling of cast Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo alloys in hydrofluoric-nitric acid solutions
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The behavior of cast Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo during chemical milling in hydrofluoric-nitric (HF-HNO3) acid solutions with 1:3 and 1:11 molar ratios was investigated using electrochemical and atomic force microscopy (AFM) techniques. Faster corrosion rate in 1:3 solutions was measured for Ti-6Al-4V than for Ti-6Al-2Sn-4Zr-2Mo, whereas in 1:11 solution Ti-6Al-2Sn-4Zr-2Mo exhibited higher corrosion rate. Scanning Kelvin probe force microscopy measurements revealed difference in the Volta potential between the a-laths and the ß-layers in the Widmansttäten microstructure indicating operation of microgalvanic cells between the microconstituents when in contact with HF-HNO3 solution. The AFM topography measurements demonstrated faster corrosion of the a-laths compared to the ß-layers, in both alloys. In 1:3 solutions, higher a/ß height difference was measured in Ti-6Al-4V, whereas in 1:11 solution, the difference was higher in Ti-6Al-2Sn-4Zr-2Mo. The results revealed that the chemical milling behavior of the two investigated alloys is controlled by the microscopic corrosion behavior of the individual microconstituents.
CitationSefer, B., Dobryden, I., Almqvist, N., Pederson, Robert, Antti, M. Chemical milling of cast Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo alloys in hydrofluoric-nitric acid solutions. "Corrosion", 1 Abril 2017, vol. 73, núm. 4, p. 394-407.