Analysis of Cracking and Delamination Processes in Sprayed Cermet and Ceramic Coatings under Biaxial Tension

摘要

In order to characterize the cracking patternsobserved in thermally-sprayed WC-Co cermet and Al_2O_3-TiO_2 ceramic coatings under nonuniform two-dimensionalstress, the hydraulic bulge test of a coated disk specimen with ahole and the punch press test of a disk specimen without a holewere conducted. The observed cracking patterns on the coatingschanged in the radial direction depending on the relativestrength of coating to interface and the stress distribution. Theappearance of the cracking patterns was explained well by"FEM Analysis-Strain Combination Method" whichaccommodates the strain of substrate with coating from elastic-plastic analysis and the strain of substrate from finite elementmethod. Moreover, the calculated sizes of cracks agreed wellwith those measured in experiments.