The Research On Process And Properties Of Laser Cladding Ni/8YSZ Composite Thermal Barrier Coatings

Laser cladding technology has become a hot research topic in recent years as a method to prepare high properties coatings,and it also has a good application prospect as a new preparation process for thermal barrier coatings.However,due to the difference in physical properties between ceramic materials and metal substrates and the characteristics of laser cladding of fast heat and fast cooling,the thermal barrier coatings are very easy to crack and peel off in laser cladding.To address this problem,in this paper,Ni/8YSZ composite thermal barrier coating s with good forming quality was prepared on 310S stainless steel by adding Ni powder to 8YSZ ceramic powder to improve the physical properties of ceramic powder and preheating treatment and laser cladding technology,and its process,bonding property and resistance under 1050°C atmosphere to high temperature oxidation and thermal shock were studied,its growth mechanism was discussed,and its oxidation and thermal shock failure mechanism was analyzed,and the conclusions were as follows:（1）Among the process parameters of laser cladding,laser power has the most obvious effect on the quality of Ni/8YSZ composite thermal barrier coatings,followed by laser scanning speed,while the beam diameter has the least obvious effect.The optimal process parameters of laser cladding for the Co Ni Cr Al Y bond coating were obtained:laser power of 1000 W,laser scanning speed of 6 mm·s^-1,beam diameter of 4.5 mm,and overlapping ratio of 22.8%.And the optimal process parameters of laser cladding for the Ni/8YSZ composite ceramic coating:laser power of 800 W,laser scanning speed of 8 mm·s^-1,beam diameter of 4.5 mm,and overlapping ratio of 32.4%.（2）The preheating treatment has a certain inhibiting effect on the crack of the thermal barrier coatings,but the effect is limited.The main effect on crack inhibition and elimination is the Ni powder of the right amount.The Ni/8YSZ composite thermal barrier coatings have good bonding property.Among them,the 15%Ni/8YSZ composite thermal barrier coatings has the best bonding property,the bonding mode is metallurgical bonding,and it is different from the laminar structure of APS and the columnar structure of EB-PVD,its microstructure is dense without cracks,and the porosity is only 0.018%.（3）The Ni/8YSZ composite thermal barrier coating s have good high temperature oxidation resistance and thermal shock resistance.Among them,the 15%Ni/8YSZ composite thermal barrier coatings has the best high temperature oxidation resistance and thermal shock resistance with the highest number of thermal cycles（29）,the smallest oxidation weight gain rate(0.110243 mg²·cm^-4·h^-1),which is 1/10 of the oxidation weight gain rate of 310S substrate.The Ni/8YSZ composite thermal barrier coatings thermostatic oxidation failure occurs at the combination of the bonding layer and the composite ceramic layer,and the oxidation failure mechanism is mainly due to the thermal stress concentration generated by the growth of TGO,which causes it to peel off.The Ni/8YSZ composite thermal barrier coatings thermal shock failure occurs inside the composite ceramic layer,and the thermal shock failure mechanism is mainly due to the thermal stress concentration gener ated by the alternation of hot and cold,which causes it to peel off.This research provides methodological ideas for solving the cracking problems of laser cladding thermal barrier coatings and ceramic coatings,and provides theoretical and experimental references for the application and development of laser cladding thermal barrier coatings.