Method for preparing a ceramic thermal barrier coating layer having excellent adhesion and thermal durability

Abstract

The present disclosure relates to a method for preparing a ceramic thermal barrier coating layer including (a) preparing a first suspension in which first oxide particles for thermal barrier coating are dispersed and a second suspension in which second oxide particles for thermal barrier coating are dispersed, respectively; (b) forming a first coating layer on a base material by suspension plasma spraying (SPS) using the first suspension; (c) forming a buffer layer on the first coating layer by the suspension plasma spraying using a mixed suspension of the first suspension and the second suspension; and (d) forming a second coating layer on the buffer layer by the suspension plasma spraying using the second suspension.

1 . A method for preparing a ceramic thermal barrier coating layer comprising:
 (a) preparing a first suspension in which first oxide particles for thermal barrier coating are dispersed and a second suspension in which second oxide particles for thermal barrier coating are dispersed, respectively;   (b) forming a first coating layer on a base material by suspension plasma spraying (SPS) using the first suspension;   (c) forming a buffer layer on the first coating layer by the suspension plasma spraying using a mixed suspension of the first suspension and the second suspension; and   (d) forming a second coating layer on the buffer layer by the suspension plasma spraying using the second suspension.   
     
     
         2 . The method of  claim 1 , wherein a first oxide for thermal barrier coating is YSZ (Yttria-stabilized zirconia) and a second oxide for thermal barrier coating is rare-earth zirconates. 
     
     
         3 . The method of  claim 2 , wherein the rare-earth zirconates are La 1.89−x Gd x Zr 2.12 O 7.06  (x is 0.24 to 1.65). 
     
     
         4 . The method of  claim 1 , wherein the step (a) comprises:
 (a-1) mechanically pulverizing an oxide powder for thermal barrier coating; and   (a-2) forming a slurry containing the pulverized oxide powder.   
     
     
         5 . The method of  claim 1 , wherein the step (a) comprises:
 (a-1) mixing two or more oxide powders to perform mechanical alloying; and   (a-2) forming a slurry containing an oxide powder for thermal spraying coating obtained in the step (a-1).   
     
     
         6 . The method of  claim 5 , wherein the two or more oxide powders comprise (i) one or more selected from Y 2 O 3 , Gd 2 O 3 , and La 2 O 3 , and (ii) one or more selected from ZrO 2  and CeO 2 . 
     
     
         7 . The method of  claim 4 , wherein the mechanical pulverizing or mechanical alloying of the oxide powder in the step (a-1) is performed by planetary ball milling, attrition milling, or shaker milling. 
     
     
         8 . The method of  claim 4 , further comprising, prior to the step (a-2), calcining the oxide powder obtained in the step (a-1). 
     
     
         9 . The method of  claim 1 , wherein, in the step (c), the buffer layer is formed so that a content ratio of the first oxide and the second oxide continuously changes in a thickness direction of a coating layer. 
     
     
         10 . The method of  claim 9 , wherein the step (c) is carried out using a suspension plasma spraying apparatus with a suspension supplier,
 wherein the suspension supplier comprises:   a first suspension storage tank in which the first suspension is stored;   a second suspension storage tank in which the second suspension is stored;   a first transfer pipe for supplying the first suspension from the first suspension storage tank to a plasma spraying gun;   a first opening/closing valve provided in the first transfer pipe for controlling a supply amount of the first suspension to the plasma spraying gun;   a second transfer pipe for connecting between the first suspension storage tank and the second suspension storage tank and for transferring the second suspension to the first suspension storage tank;   a second opening/closing valve provided in the second transfer pipe for controlling a flow rate of the second suspension to the first suspension storage tank;   a third transfer pipe for supplying the second suspension from the second suspension storage tank to the plasma spraying gun; and   a third opening/closing valve provided in the third transfer pipe for controlling a supply amount of the second suspension to the plasma spraying gun.   
     
     
         11 . The method of  claim 5 , wherein the mechanical pulverizing or mechanical alloying of the oxide powder in the step (a-1) is performed by planetary ball milling, attrition milling, or shaker milling. 
     
     
         12 . The method of  claim 5 , further comprising, prior to the step (a-2), calcining the oxide powder obtained in the step (a-1).