Application of laser cladding technology to improve the interface of thermal barrier coatings

The present study is focused on improvement of the adhesion properties of t he interface between plasma-sprayed coatings and substrates by laser claddi ng technology (LCT), Within the laser-clad layer there is a gradient distri bution in chemical composition and mechanical properties that has been conf irmed by SEM observation and microhardness measurement. The residual stress due to mismatches in thermal and mechanical properties between coatings an d substrates can be markedly reduced and smoothed out. To examine the chang es of microstructure and crack propagation in the coating and interface dur ing loading, the three-point bending test has been carried out in SEM with a loading device. Analysis of the distribution of shear stress near the int erface under loading has been made using the FEM code ANSYS, The experiment al results show clearly that the interface adhesion can be improved with LC T pretreatment, and the capability of the interface to withstand the shear stress as well as to resist microcracking has been enhanced. Copyright (C) 2000 John Wiley & Sons, Ltd.