Effect of platinum group metal addition on microstructure and corrosion behaviour of Ti–47·5 at-%Al

Abstract

Plain and alloyed titanium aluminides of composition Ti-47?5 at-%Al were prepared with the addition of 1?0 at-% platinum group metals (PGMs). The as cast alloys were subjected to potentiodynamic scans in 5, 15 and 25 wt-%HCl solutions at room temperature, and the PGM containing alloys were assessed for their abilities to spontaneously passivate by cathodic modification. Plain titanium aluminide had a duplex microstructure consisting of lamellar (a 2 and c alternating lamellae) and c-TiAl phase grains. The introduction of 1?0 at-%PGMs (platinum, palladium and iridium) led to the formation of a new phase, developing more in the c-TiAl phase grains and a general improvement of corrosion resistance by increasing the corrosion potential to nobler values. Platinum group metal additions to plain TiAl resulted in the corrosion potentials falling in the passive region of plain TiAl, indicating spontaneous passivation of PGM alloyed TiAl in 5 and 15 wt-%HCl solutions. In 25 wt-%HCl solution, the addition of PGMs shifted the cathodic process in the transpassive or active region of plain TiAl, resulting in either case in the dissolution of the alloy due to the absence of an extended passivation region. The cathodic modification of PGM alloyed TiAl occurred as a result of PGM accumulation on the surface of the TiAl alloys, which simultaneously improved the hydrogen evolution efficiency and inhibited anodic dissolution.

Additive Manufacturing Processes in Selected Corrosion Resistant Materials: A State of Knowledge Review

“…The addition shifts the cathodic process in the active region of the single Ti-Al alloy. The cathodic modification of Ti-Al alloyed with Pt group metals occurred as a result of these metals accumulating on the surface of the Ti-Al alloys, which simultaneously enhanced the hydrogen evolution efficiency and inhibited metal dissolution [99]. Overall, light metallic systems such as Ti and Al alloys are essential in the biomedical and aeronautical industries.…”

Metal and alloy spheroidisation for the Advanced Metals Initiative of South Africa, using high-temperature radio-frequency plasmas

“…The addition of precious metals such as Pd, Ru and Pt can further increase the corrosion resistance of metals and alloys, including alloys systems such as Fe-Al and stainless steels (Mwamba, Cornish and van der Lingen, 2014;Couperthwaite, 2015;Olubambi, Potgieter and Cornish, 2009), but at increasing cost.…”