Wang Ai-hua

Thermal-shock behaviour of plasma-sprayed Al2O3-13wt.%TiO2 coatings on Al-Si alloy influenced by laser remelting

Abstract A graded coating consisting of an Ni-clad Al bond layer, a 50wt.% Ni-clad Al + 50wt.% (Al 2 O 3 -13wt.%TiO 2 )intermediate layer and an Al 2 O 3 -13wt.%TiO 2 over-layer (or ceramic layer), was produced on an Al-Si alloy substrate by plasma spraying and then was remelted by laser-beam irradiating. 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 cycling, but the laser-remelted coatings show a great amount of network microcracks in the ceramic layer and only a little spallation at the interface between the intermediate layer and the bond layer. Thus the laser remelting treatment improved the spalling resistance of plasma-sprayed coating to thermal shock, but cracking resistance to thermal shock remains a problem to be solved by further investigation.

Laser modification of plasma-sprayed Al2O3-13wt.%TiO2 coatings on a low carbon steel

Abstract Plasma-sprayed Al2O3-13wt.%TiO2 coatings on a low carbon steel were laser remelted using a continuous wave CO2 laser in this investigation. After laser remelting, the plasma-sprayed ceramic coating was densified with the phase transformation from r-Al2O3+a-Al2O3+TiO2 to a-Al2O3+Al2TiO5, and the microhardness of the ceramic coating increased from 946 HV 0.2 to 1486 HV 0.2 (in particular to 2000 HV 0.2 in the upper region of the ceramic coating); also, the wear and corrosion resistance were improved significantly.