Patent ID: 6902764

Claim:
A method of coating a body with an α-alumina layer comprising: (i) bringing the body into contact with a hydrogen carrier gas containing one or more halides of aluminium and a hydrolysing and/or oxidizing agent while the body is at a temperature of 950-1000° C.; (ii) maintaining the oxidation potential of the CVD-reactor atmosphere prior to the nucleation of Al 2 O 3 at a low level, using a total predetermined concentration of oxidizing species; (iii) starting Al 2 O 3 growth by introducing the following gases into the reaction chamber: AlCl 3 , HCl and CO 2 ; (iv) adding a sulphur dopant after 20-60 min; (v) repeatedly stopping the CO 2 , AlCl 3 , HCl and the sulphur dopant for intervals of 10-50 min during which TiCl 4 is allowed to enter the reactor for 1-10 min in a concentration of 1-10%; and (vi) then reintroducing AlCl 3 , HCl, CO 2 and the sulphur dopant, in that order.