Companies are continuously under pressure to innovate their products and processes. In
Portugal, there are already several examples of enterprises that have chosen research groups,
associated to universities, to straighten collaboration seeking the development of new materials and
advanced technological processes, to produce components with complex shapes, high surface
quality, and others, at low cost, for continuously more demanding applications. Unfortunately, these
cases are still a very small number, and many efforts have to be done to enlarge the collaboration
university-companies. Ti and other reactive alloys are important groups of metals that are under
intense and continuous research and development. For example, the high mechanical properties, low
density, osteointegration behavior, corrosion resistance to fluids and tissues of the human body, the
ability to be sterilized, and the possibility to obtain complex shapes, makes Ti a very attractive
material for medical applications. The investment casting process, using lost wax or lost rapid
prototyping models, allows designers a great amount of freedom and capacity to quickly produce
castings of high dimensional accuracy and excellent surface quality suitable for different
applications. Many of the castings obtained by this process are immediately ready for use, avoiding
costly machining operations and joining processes, making the process very attractive to produce
precision parts in Ti and other reactive alloys. However, the high reactivity of the Ti raises several
compatibility problems with the traditional materials employed on the ceramic shells for casting
steels and non ferrous alloys. The fragile surface layer obtained on the interface Ti-ceramic shell,
result of the Ti reaction with oxygen and nitrogen of the shell, significantly reduces the mechanical
properties of the cast parts, making them useless. The aim of the present work is the study of the
interface properties of the Ti-ceramic shell, in order to be able to manufacture ceramic shells of low
chemical reactivity for the investment casting process of reactive alloys, namely; titanium alloys,
inconel, aluminotitanates, and others. Ceramic shells manufactured with calcium and yttria
stabilized zirconia and other non reactive ceramics were employed and the metallic interface
characterized in terms of microscopic and microhardness properties.
Optimization of Ceramic Shells for Contact with Reactive Alloys
