The commercial availability of ever more efficient gas turbines has always been paced by the results of research and development in the concurrent fields of design and materials technology. Improved structural design and airfoil cooling technology applied to higher strength-at-temperature alloys cast by increasingly complex methods, and coat4d with steadily improved protective coating systems, have led to remarkably efficient turbine machinery for aircraft propulsion and power generation. For first state turbine blades, nickel-based superalloys in various wrought and cast forms, and augmented by coatings since the sixties, have been singularly successful materials systems for the past fifty years - and still no real world substitutes are on the horizon.

This presentation traces the history of protective coatings for superalloy airfoils beginning with the simple aluminides, followed by these same modified with silicon, chromium and platinum, then MCrAlY overlay coatings, and finally the elegant electron beam vapor deposited ceramic thermal barrier coatings recently introduced to servcie. The publicly available results of several decades of research supporting these advances are acknowledged. The most important of these include generic research on oxidation and hot corrosion mechanisms of superalloys and coatings, the intricacies of protective oxide adherence, mechanisms of low temperature (Type II) hot corrosion, and alumidice coating formation.

With no promising practical materials systems beyond coated nickel-base superalloys apparent in the foreseeable future, continued progress will likely be made by further refinement of control of oxide adherence, and by more cost effective manufacturing processes for contemporary types of protective coatings.

EB-PVD circonia thermal barrier coatings have several advantages over coatings deposited with other techniques. Therefore EB-PVD coaters for deposition of turbine blades are becoming increasingly interesting. This applies to pilot coaters as well as to production coaters.

Electron beams are not only suited for generating the evaporation process, they are also excellently suitable for preheating the turbine blades. By means of an electron beam preheating process the different parts of the rotating turbine blades (which are partially coverd to prevent coating of this part) can be heated without temperature differences. Moreover, they can be heated faster than by means of the conventional radiation heating. The possibility of unretarded electron beam guidance creates the opportunity to generate very fast alternating heating patterns with matched changes of the power distribution on several parts of the turbine blade.

The developed EB-heating technology permits for blades have a weight of more than 7 kg a synchronized temperature increase to 1000°C within less than 15 minutes. This helps to shorten the vacuum cycle time per charge and increases the capacity of the coating plant. A modern conception of an EB-PVD production coater for circonia thermal barrier coating on turbine blades containing the new EB-heating process will be introduced.