Ceramic heat insulating coating of columnar structure - with high thermal cycling resistance, especially for gas turbine blade.

Abstract
A novel component consists of a base bearing a ceramic heat insulating layer of columnar structure, the columns being normal to the base surface and having a mean diameter of <2.5 (preferably 0.5-2.0) mu m. Preferably, the layer consists of a 'metal-ceramic' material, especially ZrO2 stabilised with e.g. Y2O3, and the base consists of metal, especially a Ni or Co base alloy. Also claimed is a coating apparatus used to produce a heat insulating layer on a base and including (a) a holder (8) for positioning the base (2); (b) a hollow cathode arrangement (10) which allows inert gas passage and which has a cathode material (11), an anode (12), an inert gas inlet (14) and a gas outlet (13) facing the holder (8); and (c) an additional separate heater (9) for heating the base (2). Further claimed is a process for vacuum coating a base with a heat insulating layer by (i) ionising an inert gas in an oxygen-free atmosphere; (ii) using the ionised inert gas to detach metal atoms from a metallic c athode material and to entrain the atoms towards the base; and (iii) supplying oxygen to form a metal oxide before the inert gas stream reaches the base or to oxidise already deposited metal, the base being heated to a predetermined nucleation temperature of above 800 (preferably 950-1050) deg. C. USE - Used especially for coating blades or other heated components e.g. heat shields, of gas turbines. ADVANTAGE - The heat insulating layer has high thermal cycling resistance.