Weigang Hua

Oxidation behavior of thermal barrier coatings obtained by detonation spraying

Thermal barrier coatings (TBCs) have been successfully obtained by detonation spraying, through optimizing the spray parameters (especially the ratio of C2H2 to O-2). The oxidation behaviors of detonation sprayed TBCs at 1000 and 1100 degreesC were studied. The results indicated that the detonation sprayed TBCs were uniforin and dense, with a few microcracks in the ceramic coats and a rough surface of bond coats. At the high temperature, the dense detonation sprayed ceramic coats with low porosity could obviously decrease the diffusive channels for oxygen and reduce the oxygen pressure (PO2) at the ceramic/bond coat interface. Under the lower oxygen pressure at the interface, it was advantageous to the formation of a continuous protective Al2O3 layer and the growth of a thermally grown oxide layer (TGO) obeyed the fourth power law

The depth distribution of residual stresses in (Ti,Al)N films : Measurement and analysis

A method is introduced to determine the depth distribution of the residual stresses in (Ti,Al)N films. The films were gradually stripped by chemical corrosion, an optical system was designed to test the curvature change of the specimens, and the depth distribution of the residual stresses was calculated. The results show that the residual stresses increase gradually from the interface of film/substrate and reach a maximum value at the middle region, then decrease until the surface.