Alloy, protective layer and component
Known protective layers having a high Cr-content and a silicone in addition, form brittle phases that embrittle further under the influence of carbon during use. The protective layer according to the invention is composed of 22% to 26% cobalt (Co), 10.5% to 12% aluminum (Al), 0.2% to 0.4% Yttrium (Y) and/or at least one equivalent metal from the group comprising Scandium and the rare earth elements, 15% to 16% chrome (Cr), optionally 0.3% to 1.5% tantal, the remainder nickel (Ni).
1. A protective single layer for protecting a component against corrosion and/or oxidation, the component having a substrate which is nickel-based or cobalt-based and the single layer resides on the substrate,
wherein the single layer has the composition of an alloy, which consists of: 22% wt % to 26% wt % cobalt (Co), 15% wt % to 16% wt % chromium (Cr), 10.5% wt % to 12% wt % aluminum (Al), at least 0.3% wt % of tantalum and a maximum of 1.5% wt % tantalum, a total of 0.2% wt % to 0.6% wt % of yttrium (Y), and the balance nickel (Ni),
wherein no silicon precipitates are formed during use at least at 950° C. or at least at 1100° C., thereby preventing embrittlement of the alloy during use at least at 950° C. or at least at 1100° C., and
the protective single layer is applied by plasma spraying,
wherein the Co content extends the beta/gamma field and avoids the alpha phases at least at 950° C. or at least at 1100° C.,
wherein the Cr content increases the activity of Al for the Al 2 O 3 formation and avoids alpha chromium or sigma phase at least at 950° C. or at least at 1100° C.,
wherein the Al content forms a stable Al 2 O 3 layer and avoids embrittlement at least at 950° C. or at least at 1100° C.,
wherein the Y content forms sufficient Y aluminate for the formation of Y-containing pegs with low oxygen contamination and negatively accelerates the oxide layer growth of the Al 2 O 3 layer at least at 950° C. or at least at 1100° C.,
wherein the Ta content stabilizes the γ′ phase or shifts the transition to a higher temperature to slow down phase degradation by consumption of aluminum at least at 950° C. or at least at 1100° C., and
wherein the single layer protects the substrate against corrosion and oxidation at least at 950° C. or at least at 1100° C. and is ductile enough to be able to accommodate possible deformations of the substrate and not crack to avoid providing points of attack for oxidation and corrosion at least at 950° C. or at least at 1100° C.
2. The protective single layer as claimed in claim 1 , wherein the alloy consists of 0.5 wt. % yttrium (Y).
3. A component of a gas turbine, having a substrate of the component which is nickel-based or cobalt-based, and the protective single layer as claimed in claim 1 thereon, configured to protect against corrosion and oxidation at high temperatures.
4. The component as claimed in claim 3 , further comprising a ceramic thermal barrier layer applied onto the protective single layer.
5. The protective single layer as claimed in claim 1 , wherein the alloy consists of at least 0.5 wt. % of tantalum.