MICROSTRUCTURE OF LASER_CLADDED Al_2O_3+TiO_2 COMPOSITE CERAMIC COATING
Chen Chuanzhong (Institute of Materials Science and Engineering, Shandong University of Technology, Jinan 250061)
The microstructure and phase composition of laser_cladded Al_2O_3+TiO_2 composite ceramic coatings on 45# steel are studied. The results show that lamellas structure characteristics of plasma_sprayed coatings have been eliminated, and columnar grains are formed approximately along the heat conducting direction after laser cladding, and the Al_2O_3+TiO_2 composite ceramic coating consists of α-Al_2O_3,TiO_2, ~γ-Al_2O_3 and Al_2TiO_5. Ti and a small amount of Cr,Fe,Y elements from the bond coating appear in the columnar grain of ~α-Al_2O_3. The grain boundary consists of Al_2TiO_5 phase formed by Al_2O_3 and TiO_2, in which a part of Ti is replaced by a small amount of Cr, Fe and Y elements from the bond ~coating. *#The bond coating consists *#of*# γ-Ni*# based *# solid*# solution containing Fe,Cr,Al and Y elements, and γ′-(Ni,Fe)_3Al phase distributes dispersedly on it. There is a metallurgical combination interface between the bond coating and substrate. The interface between the ceramic coating and the bond coating has been improved obviously.