Abstract: A mask suitable for protecting a portion of a substrate surface against diffusion coating of the substrate with a metal, which mask comprises a ceramic material comprising silica and an inert refractory diluent and a metal or metal alloy, wherein the metal or metal alloy is one which is reactive with silicon thereby minimising or preventing siliconisation of the substrate with silicon in the ceramic material under conditions of diffusion coating, and which is reactive with the metal being applied by diffusion coating thereby preventing diffusion coating of the portion of the substrate surface it is desired to protect.

Abstract: A metallic article (30) comprises a bond coating (34) on the metallic article (30) and a ceramic thermal barrier coating (38) on the bond coating (34). The ceramic thermal barrier coating (38) comprises a plurality of columnar grains (40) extending substantially perpendicular to the surface of the metallic article (30). The ceramic thermal barrier coating (38) has an inner portion (44), a transition portion (46) and an outer portion (48). Each columnar grain (40) has a substantially constant cross-sectional area throughout its length in the outer portion (48), has smooth surfaces and there are distinct uniform gaps (42) between columnar grains to minimize the stress/strain in the columnar grains (40) and/or to minimize the stress/strain between adjacent columnar grains (40) and thereby increases the resistance to spallation of the ceramic thermal barrier coating. The columnar grains (40) are produced by controlling the evaporation rate of the ceramic, the temperature and speed of rotation of the article (30).

Abstract: A multi-layer thermal barrier coating for a superalloy article includes a metallic matrix coating containing particles, a MCrAlY alloy bond coating on the metallic matrix coating, a thin oxide layer on the MCrAlY alloy bond coating and a columnar grain ceramic thermal barrier coating. The metallic matrix coating includes a 80 wt % nickel-20 wt % chromium alloy. The particles include metallic compounds such as carbides, oxides, borides and nitrides, which react with harmful transition metal elements such as titanium, tantalum and hafnium, in the superalloy substrate. One suitable compound is chromium carbide because the harmful transition metal elements will take part in an exchange reaction with the chromium in the chromium carbide to form a stable carbide of the harmful transition metal element. This reduces the amount of harmful elements in the superalloy reaching the oxide layer and increases the service life of the thermal barrier coating.

Abstract: A metallic article includes a bond coating and a ceramic thermal barrier coating on the bond coating. The ceramic thermal barrier coating includes a plurality of columnar grains, which extend perpendicularly to the surface of the metallic article. Each columnar grain includes a plurality of layers. Some of the layers include sub-grains extending at an acute angle to the surface of the metallic article to form voids between adjacent sub-grains. The voids are arranged at an acute angle to the surface of the metallic article and reduce the thermal conductivity of the ceramic thermal barrier coating. Some of the layers include sub-grains extending perpendicularly to the surface of the metallic article to provide erosion resistance.

Abstract: A ceramic thermal barrier coating layer for a superalloy article is caused to adhere to the superalloy article by applying platinum to the superalloy article and heat treating at a temperature of 1100.degree. C. to 1200.degree. C. for one hour. This causes aluminum to diffuse from the superalloy article into the platinum to form a platinum enriched outer layer which generally includes a platinum enriched gamma phase and a platinum enriched gamma prime phase. An alumina layer is formed between the platinum enriched outer layer and a ceramic coating. The platinum enriched gamma phase and the platinum enriched gamma prime phase in the outer layer reduces the migration of transition metal elements to the ceramic coating to enable a very pure alumina layer to be formed.

Abstract: A multi-layer thermal barrier coating (42) for a superalloy article (40) comprises a platinum enriched superalloy layer (44), an MCrAlY bond coating (46) on the platinum enriched superalloy layer (44), a platinum enriched MCrAlY layer (48) on the MCrAlY bond coating (46), a platinum aluminide coating (50) on the platinum enriched MCrAlY layer (48), an oxide layer (54) on the platinum aluminide coating (50) and a ceramic thermal barrier coating (56) on the oxide layer (54). The platinum aluminide coating (50) and the platinum enriched MCrAlY layer (48) reduce movement of transition metals from the superalloy substrate (40) and the MCrAlY bond coating (46) to the oxide layer (54) so that the oxide layer is very pure alumina.

Abstract: A superalloy turbine blade (10) has a MCRALY bond coating (22) and a thermal barrier coating (24). The thermal barrier coating (24) comprises a plurality of alternate layers (25, 27) which have different structure to produce a plurality of interfaces (26) substantially parallel to the metallic substrate (20)/ bond coating (22) interface. These interfaces (26) provide paths of increased resistance to heat transfer to reduce thermal conductivity of thermal barrier coating (24). The structure in the alternate layers (25, 27) of the thermal barrier coating (24) is columnar (28), or segmented, to ensure that the strain tolerance of the thermal barrier coating (24) is not impaired. The columnar grains (28) in the layers (25, 27) extend substantially perpendicular to the metallic substrate (20)/ bond coating (22) interface. This enables thermal barrier coating (24) of reduced thickness and weight to be used.

Abstract: A ceramic thermal barrier coating layer for a superalloy article is caused to adhere to the superalloy article by applying platinum to the superalloy article and heat treating at a temperature of 1100.degree. C. to 1200.degree. C. for one hour. This causes aluminum to diffuse from the superalloy article into the platinum to form a platinum enriched outer layer which generally includes a platinum enriched gamma phase and a platinum enriched gamma prime phase. An alumina layer is formed between the platinum enriched outer layer and a ceramic coating. The platinum enriched gamma phase and the platinum enriched gamma prime phase in the outer layer reduces the migration of transition metal elements to the ceramic coating to enable a very pure alumina layer to be formed.

Abstract: A coated article includes a superalloy substrate, an intermediate bond coat and a thermal barrier coating. The bond coat may include a platinum aluminide layer underlying a thin oxide layer. The thin oxide layer may include alumina. The coated article has high strength and durability at high temperatures over extended periods of time and thus is especially useful in the form of, e.g., a turbine blade or turbine vane.