THERMAL-SHOCK BEHAVIOR OF PLASMA-SPRAYED AL2O3-13WT-PERCENT-TIO2 COATINGS ON AL-SI ALLOY INFLUENCED BY LASER REMELTING

A graded coating consisting of an Ni-clad Al bond layer, a 50wt.% Ni-c lad Al + 50wt.% (Al2O3-13wt.%TiO2) intermediate layer and an Al2O3-13w t.%TiO2 over-layer (or ceramic layer), was produced on an Al-Si alloy substrate by plasma spraying and then was remelted by laser-beam irrad iating. The thermal-shock resistance of the plasma-sprayed coating and the laser-remelted coating was investigated in this study. The plasma -sprayed coatings show a lot of spallation at the different depths of coatings and a few macrocracks in the ceramic layer during thermal cyc ling, but the laser-remelted coatings show a great amount of network m icrocracks in the ceramic layer and only a little spallation at the in terface between the intermediate layer and the bond layer. Thus the la ser remelting treatment improved the spalling resistance of plasma-spr ayed coating to thermal shock, but cracking resistance to thermal shoc k remains a problem to be solved by further investigation.