Thermally sprayed gastight protective layer for metal substrates

Abstract

In a thermally sprayed, gastight protective layer for metal substrates, especially those based on Fe, Ni, Al, Mg and/or Ti, wherein the spray powder for the purpose comprises at least two components, of which the first is a silicate mineral or rock and the second is a metal powder and/or a further silicate mineral or rock, the silicate mineral or rock component in the spray powder has an alkali content of less than 6 per cent by weight.

1 . A thermally sprayed, gastight protective layer for metal substrates, especially those based on Fe, Ni, Al, Mg and/or Ti, wherein the spray powder for the purpose comprises at least two components, of which the first is a silicate mineral or rock and the second is a metal powder and/or a further silicate mineral or rock, characterized in that the silicate mineral or rock component in the spray powder has an alkali content of less than 6 per cent by weight. 
     
     
         2 . A protective layer according to  claim 1 , characterized in that metal powder comprises a nickel-base or copper-base alloy. 
     
     
         3 . A protective layer according to  claim 1 , characterized in that the at least one silicate component of the spray powder comprises natural or synthetically produced minerals or rocks. 
     
     
         4 . A protective layer according to  claim 1 , characterized in that the spray powder is composed of three components, namely of a first and a second silicate mineral or rock and of a metal powder. 
     
     
         5 . A protective layer according to  claim 1 , characterized in that the spray powder contains a content of at least 10 per cent by weight of a silicate component having a content of >99% SiO 2 . 
     
     
         6 . A protective layer according to  claim 1 , characterized in that the protective layer has a thermal conductivity of between 0.8 and 5 W/mK. 
     
     
         7 . A protective layer according to  claim 1 , characterized in that the protective layer has a layer thickness of 100 to 2500 μm. 
     
     
         8 . A protective layer according to  claim 1 , characterized in that the protective layer has a layer thickness of greater than 2 mm. 
     
     
         9 . A spray powder composed of at least two components for production of a protective layer according to  claim 1 . 
     
     
         10 . A method for production of a protective layer according to  claim 1 , wherein the application of the protective layer on the metal substrate takes place by means of flame spraying, high-velocity oxygen-fuel flame spraying (HVOF) or plasma spraying, characterized in that the coefficients of thermal expansion of layer and substrate are adapted during application of the protective layer by controlled partial devitrification of the mineral components of the spray powder. 
     
     
         11 . A method for production of a protective layer according to  claim 10 , characterized in that the partial devitrification is controlled by suitable choice of the particle sizes of the at least one silicate component of the spray powder. 
     
     
         12 . A method according to  claim 10 , characterized in that the protective layer acquires a fissure-free microstructure and good adhesion to the substrate by vitrification of at least one mineral component while it is being applied. 
     
     
         13 . The use of a protective layer according to  claim 1  for protection of substrates such as parts of the combustion chambers of an internal combustion engine or of a gas turbine from high temperatures, corrosion and erosion.