Electrolytic Etching of Platinum-Aluminium Based Alloys

Abstract

The microstructures of as-cast and annealed platinum alloys of different compositions were revealed after electrolytic etching in hydrochloric acid/sodium chloride solution using direct current. It was shown that the etching process enhances good microstructural images of platinum-aluminium based alloys.

High-order additions to platinum-based alloys for high-temperature applications

“…They were also harder than the eight ternary Pt-Al based alloys investigated by Hill (2001), where the hardest alloy had a Vickers hardness of 530 HV. However, Pt-Al-V (Odera et al, 2012a;Odera, 2013) and Pt-Cr-V alloys (Odera et al, 2012b;Odera, 2013) and Pt-Al-Cr alloys (Süss, 2007) were generally much harder than the current as-cast alloys, because many of the Pt-Al-V and Pt-Cr-V alloys contained the hard Pt-V intermetallic phases. The high hardness of some of the Pt-Al-Cr alloys was attributed to ~PtAl 2 , ~PtAl, and ~Pt 2 Al 3 .…”

“…Alloy buttons weighing ~2 g each were prepared for compositions chosen (Tables I and II) from previous work (Ndlovu, 2006;Shongwe et al, 2008Shongwe et al, , 2010Mulaudzi, 2009;Samal and Cornish, 2010;Odera et al, 2012aOdera et al, , 2012bOdera, 2013) for a series of alloys based on Pt-Al-Cr-Ru with additions of Nb and/or V. The elemental components had 99.9% purity, except for V (99.6% purity). The samples were manufactured by arc-melting under argon, on a water-cooled copper hearth, with Ti as an oxygen-getter, and each was turned over and re-melted three times in an attempt to achieve homogeneity.…”

“…Microhardness tests were performed after etching in a solution of 10 g NaCl in 100 cm 3 HCl (32% vol. concentration), using a DC power supply and a voltage range of 9 V to 12 V (Odera et al, 2012c). A Vickers microhardness tester was used with a load of 300 g, and at least five measurements taken.…”

“…This could counteract the effect of the Al-Pt eutectic with the decreasing (Pt) melting point. In order to predict the effect of Nb and V on the Pt-based alloys, phase diagrams were studied for (which had not been reported before): Pt-Al-Nb (Ndlovu, 2006;Samal and Cornish, 2010) and Pt-Cr-Nb (Mulaudzi, 2009), as well as Pt-Al-V (Odera et al, 2012a;Odera, 2013a) and Pt-Cr-V (Odera et al, 2012b;Odera, 2013a). The results indicate how the additions affect the microstructure and give an idea of the maximum additions without losing the two-phase structure, or forming other phases.…”