Experimental and Modeling Studies of Thermal Barrier Coating Failure Under Isothermal Oxidation and Solid Particle Erosion

TBC (Thermal Barrier Coating) with YSZ-Al2O3/YSZ as top coat (TC) and MCrAlY alloy as bond coat (BC) marked as YSZ-Al2O3/YSZ double layer TBC was used for thermal barrier material on rocket nozzle wall. Several test have been conducted (thermal test and SEM-EDX). Thermal test was divided into two part, Thermal Torch and Non-isothermal Oxidation Test which is used for measure the resistance of TBC structure against oxyacethylene flame penetration as a miniature of thermal static test for rocket nozzle until the specimen was failure and used to measure the resistance against non-isothermal oxidation as well as investigate the growth of TGO (Thermally Grown Oxide) layer on interface between TC/BC for thermal torch and non-isothermal oxidation test respectively. This test was performed at 1100o C with 10°C/min heating rate. The results showed that the improvement of feed rate on topcoat powder gave the effect on the surface morphology of topcoat. Lower feed rate bring in a coarse surface morphology and tend to be porous. Al2O3/YSZ composite layer affect on the growth of TGO layer after thermal test, which indicates the lower growth of TGO especially for 15%Al2O3/8YSZ. TGA test showed that the sample began to oxidize at temperature range c.a 1000 – 1030°C, however 1st derivative analysis indicated that 15% Al2O3/8YSZ, 14 g/min was the most stable sampel. Moreover this material has a good resistance from torch destruction.

Download Full-text

Interfacial Fracture Toughness of APS Thermal Barrier Coating under High Temperature

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.348-349.181 ◽

2007 ◽

Vol 348-349 ◽

pp. 181-184 ◽

Cited By ~ 3

Author(s):

Hong Yu Qi ◽

Xiao Guang Yang ◽

Rui Li

Keyword(s):

Fracture Toughness ◽

High Temperature ◽

Thermal Barrier Coating ◽

Interfacial Fracture ◽

Isothermal Oxidation ◽

Thermal Barrier ◽

Interfacial Fracture Toughness ◽

Air Plasma ◽

Bond Coating ◽

Barrier Coating

Thermal barrier coating (TBC) is an essential requirement of a modern gas turbine engine. The TBC failure is the delamination and spallation. The oxidation damage under high temperature results in the reduction of interfacial adhesion. The interfacial fracture toughness is an important property to analyze the TBC failure. The interfacial fracture toughness of ceramic coating - bond coating has been researched in the past. However, the facture toughness of the bond coating - substrate due to the Al depletion was very few studied. In this study, a NiCrAlY bond coating by air plasma spray (APS) was deposited. The substrate was directionally solidified superalloy (DZ40M). Isothermal oxidation was performed at 10500 for 100h. Using the HXZ-1000 micro-hardness equipment, the five different times was chosen to test the hardness and the crack length, and then the fracture toughness was obtained. While the oxidation exposure time increased at 10500, the hardness of the substrate close to the bond coating decreased with the increase of the bond coating’ hardness. Meanwhile, the interfacial fracture toughness of the bond coating - substrate decreased because of the Al depletion.

Download Full-text