Method for the Production of Thin Dense Ceramic Layers

Abstract

The invention relates to a method for the production of a thin dense ceramic layer on a substrate by means of atmospheric plasma spraying, whereby the following steps are carried out: a) the substrate is pre-heated to a temperature corresponding to at least a quarter of the melting point of the ceramic for application in Kelvin, b) a ceramic powder or a ceramic powder mixture with d 50 -values of less than 50 gm is used as spray adjunct, c) particle speeds at incidence on the substrate of more than 200 m/s are set, d) particle temperatures are set such that on incidence on the substrate surface the particles have a temperature at least 5% above the melting point of the ceramic for application in Kelvin, e) the amount of the spray adjunct and passage speed of the plasma burner are set such that on a single pass of the substrate a layer thickness of less than 100 ?m is achieved, f) a thin and also gas-tight layer is generated on the substrate with a single pass of the substrate which has a leakage rate of less than 10 −1 mbar L/(cm 2 s).

1 . A method for producing a thin dense ceramic layer on a substrate by atmospheric plasma spraying, comprising the following steps: 
 preheating the substrate to a temperature corresponding to at least one-fourth of the melting temperature, in Kelvin, of the ceramic to be applied,    using a ceramic powder or ceramic powder mixture having d 50  values less than 50 μm as spray additive,    setting incident particle speeds on the substrate at greater than 200 m/s,    setting particle temperatures such that upon incidence on the substrate surface the particles have a temperature that is at least 5% greater than the melting temperature; in Kelvin, of the ceramic to be applied,    setting the quantity of the spray additive and the travel speed of the plasma burner such that a layer thickness of less than 100 μm is achieved by a single pass over the substrate,    producing a thin and also gas-tight layer having a leakage rate of less than 10 −1  mbar L/(cm 2  s).    
     
     
         2 . The method according to preceding  claim 1 , further comprising the step of 
 using a ceramic powder or ceramic powder mixture having d 50  values less than 30 μm as spray additive.    
     
     
         3 . The method according to  claim 1 , further comprising the step of 
 introducing the powder introduced into the plasma flame in the form of a suspension.    
     
     
         4 . The method according to  claim 1 , further comprising the step of 
 setting incident particle speeds on the substrate at greater than 250 m/s.    
     
     
         5 . The method according to  claim 1 , further comprising the step of 
 setting particle temperatures such that upon incidence on the substrate surface the particles have a temperature that is at least 10% greater than the melting temperature, in Kelvin, of the ceramic to be applied.