Hot-salt corrosion PT-7M, 42ХНМ, Inconel 690 and Incoloy 800 Alloys

Investigation of Microstructure and Corrosion Resistance of Ti-Al-V Titanium Alloys Obtained by Spark Plasma Sintering

“…In particular, for the Ti5Al2V alloy it was ~1160-1170 MPa. The value of σ b is close to the tensile strength of the Ti5Al2V alloy after equal channel angular pressing (~1050 MPa) [46]. The magnitude of tensile strength of the Ti and Ti6Al4V alloy obtained by SPS were also very high and reached 570-580 MPa and 1030-1040 MPa, respectively.…”

“…It should be noted that the Ti alloys obtained by SPS have rather high hardness (1.3-1.5 times higher than the hardness of the coarse-grained alloys with similar composition obtained by traditional technology of hot deformation in the β-region). In particular, hardness of the Ti5Al2V alloy obtained by SPS (3.3-3.4 GPa) was considerably higher than the one of the coarse-grained Ti5Al2V alloy with the grain sizes 10-50 µm (~2.0-2.1 GPa [39,46]). It is a quite unexpected result since the microstructure parameters of the Ti alloys obtained by SPS and by traditional hot deformation method are close enough.…”

“…The mean depths of the corrosion defects in the Ti5Al2V and Ti6Al4V alloys were 40-50 µm and 20-40 µm, respectively. Note that the average depth of the corrosion defects in the Ti5Al2V alloy specimens obtained by SPS (40-50 µm) was considerably lower than in the coarse-grained Ti5Al2V alloy specimens in the initial state tested in the same HSC conditions (~400-600 µm [46]). This conclusion agrees qualitatively with the results of investigation of the specimens' mass changes after corrosion testing.…”

“…Note that more uniform equiaxial microstructure was formed in the Ti5Al2V alloy than in the Ti6Al4V. The boundaries of the α-phase grains in the Ti6Al4V alloy had a lighter contrast in Z-contrast mode that evidences the nucleation of β-phase particles at the α-phase grain boundaries (Figures 2d and 3, see [39,46,47]). Similar "light" grain boundaries were found in the Ti5Al2V alloy as well although the volume fraction of these ones was lower than in the Ti6Al4V alloy considerably (Figure 3).…”

“…The autoclave testing for hot salt corrosion was performed in a mixture of NaCl and KBr (300:1) at 250 • C according to the technique described in [46] in the conditions of oxygen access. The testing time was 500 h. The degree of the corrosion damage was evaluated according to Russian National Standard GOST 9.908-85.…”