Ceramic coatings obtained on superalloys modified by laser treatment

The paper presents the influence of laser-beam remelting of Al ₂0₃-Ni ceramic layers spread on creep-resisting alloy by means of plasma spray upon the quality of ceramic coatings, which form thermal barrier and high temperature corrosion shield of these alloys. The examination showed that 0.103-109 W/m² power density laser-beam scanning ensures good quality of coatings at beam moving rate 1 to 2 m/min. At smaller scanning rate, laser remelted ceramic layer spalls and chips. Better quality of the ceramic coatings can be obtained by diffusive chromoaluminizing applied prior to laser remelting. Laser-beam remelting conditions of such layers, elaborated in the course of examination, ensure pores fading, decrease of remelted layer thickness and increase of base adhesion without cracks, chips and spalls. Additionally remelted zone features either strong break up of structure or the structure is amorphic with unchanged chemical composition as to the matrix chemical composition. Obtained results are the base for the elaboration of thermal barrier technology and the technology of anticorrosion shield for creep - resisting alloys applied in high temperature power engineering.