Microstructure And Properties Of Thermal Barrier Coatings By High Frequency Light Vibrating Assisted Laser Cladding

The preparation of ZrO_2-8%Y₂O₃ coating were studied on the surface of Ti-6Al-4V alloy by laser cladding and high frequency light vibrating assisted laser cladding, respectively. Select the best laser laser cladding parameters.The phase constituents and microstructure of the coating were analyzed by X-ray diffractometer（XRD）, scanning electron microscope（SEM） and optical microscope（OM）. The microhardness and thermal shock properties of two kinds of thermal barrier coatings were further examined.Experimental of laser cladding results show that the optimized laser cladding parameters for coating are laser power of 2000 W, scanning speed of 400mm/min, light spot diameter of 5 mm and the overlapping coefficient of 40%. Coating the surface smooth, corrugated cladding layer, the presence of a small amount of micro-cracks and macro pores; Coating by high frequency light vibrating assisted laser cladding using the optimized process parameters, get the best vibration frequency is 926 HZ. Compared with direct preparation of laser cladding coating the surface quality improved, cladding color lighter, relatively smooth surface, is an ideal cladding surface morphology.Thermal barrier coating prepared by laser cladding microstructural analysis shows that the coating consists of t-ZrO₂ and c-ZrO₂ phase, After laser cladding coating m phase diffraction peaks relatively weakened, coatings significantly reduced m phase content. Under certain scan speed and the amount of defocus, coating porosity increases with laser power is gradually reduced, the pores and cracks are mainly concentrated in the bottom of the cladding layer, cracks increased with increasing laser power. Compared with direct thermal barrier coatings prepared by laser cladding, decreased coating pores and cracks, the coating dendrites significant reduction, grain refinement, mainly isometric crystal forms exist. Micro-component analysis and line scan results indicate that a uniform coating of the components within the high frequency light vibration effect. Nanostructures ZrO_2-8% Y₂O₃ coating after laser cladding exhibit features streamlined organization, which does not melt the particles along the flow lines are regularly distributed uniformly in the bath.The average hardness of the cladding layer is about 1100HV_0.2, which was 3.5 times the hardness of the substrate. The microhardness obtained after high frequency light vibrating assisted laser cladding was up to 1300 HV_0.2, which was higher than that of the microhardness of the direct laser cladding coating.Two kinds of thermal barrier coatings all exhibited excellent thermal shock properties. Direct laser cladding coatings produced about 15% of the area appeared to fall off after thermal shock 7 times, the thermal barrier coating prepared by high frequency light vibrating assisted laser cladding coating is about 11 times. The thermal shock property of the high frequency light vibrating assisted laser cladding coating are about 1.5 times higher than that of the direct laser cladding coatings.