Several rings of varying geometries were cast using a range of platinum alloys. Different flask temperatures (ranging from 100°C to 800°C) were used, as well as different investment powders (both the conventional type needing long burnout times as well as the "shock-heat" type). The objective was to assess how the different platinum alloys were affected by these parameters. The quality of the cast items was evaluated in terms of filling, homogeneity, porosity, hardness, grain size and the presence of any inclusions by making use of visual inspection, optical microscopy and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The removal of investment material from the casting was also considered.

Author: Rainer Süss, Peter Lester, Stefanie S. Taylor