Materials Science and Chemistry

Biography

Biography: Maryam Ali Bash

Abstract

The backbone for thermal barrier coatings has been well recognized as zirconia based ceramics which are mostly produced using plasma spraying techniques. Defects which have been usually present in plasma sprayed coatings may lead to easily penetrate the harmful species in the fuel and then diffused into the coating which leading to accelerate degradation. The work summarizes the important highlight points relative to the gas and solid state lasers processing of advanced plasma sprayed coatings used in advanced thermal barrier coatings turbine engines. The reduction or even elimination of these problems during servicing using CO₂, Nd³⁺-YAG and Yb³⁺-YAG lasers can highly improve the lifetime of the TBCs systems. The paper reports and analyzed all the relevant works of laser sealing of plasma sprayed coatings. The recent work by the authors has been investigated the effect of processing and laser parameters of continuous wave high power solid state Yb³⁺-YAG fiber laser on sealing thermal plasma sprayed zirconia-ceria-yttria thermal barrier coating. It was found that the sealed coatings having shinny appearance, dense microstructure with nearly nil depressions and very low thickness evaporation. They also postulated that the sealed coatings characterized with very fine cell size, very low roughness and having network crack spacing. These network crack spacing were formed due to sever laser thermal shock associated with high temperature gradient. The network crack spacing improves considerably the strain tolerance of the thermal barrier coating system and finally enhances the durability. Many different mathematical relationships were deriving between the output performances and the dependent laser variables of power density, interaction time and specific energy.

Showing yellow colour after restoring of oxygen.