Y_(2)O_(3)含量对大气等离子喷涂Al_(2)O_(3)-Y_(2)O_(3)复合涂层微观结构和力学性能的影响

Effect of Y_(2)O_(3)Content on Microstructure and Mechanical Properties of Al_(2)O_(3)-Y_(2)O_(3)Composite Coatings Deposited by Atmospheric Plasma Spraying

目的探究掺杂不同质量分数Y_(2)O_(3)对Al_(2)O_(3)-Y_(2)O_(3)复合涂层微观结构及其力学性能的影响。方法采用大气等离子喷涂制备Al_(2)O_(3)涂层,以及Y_(2)O_(3)质量分数分别为10%、20%、30%、40%的Al_(2)O_(3)-Y_(2)O_(3)复合涂层。利用SEM、EDS对粉末以及不同涂层的形貌、组织结构、元素分布进行分析。使用XRD表征粉末和涂层的物相。使用显微硬度仪、纳米压痕测试仪和电子万能试验机对涂层的显微硬度、弹性模量以及断裂韧性等力学性能进行测试分析。结果Al_(2)O_(3)喷涂粉末的物相由α-Al_(2)O_(3)组成,而喷涂得到的Al_(2)O_(3)涂层则由α-Al_(2)O_(3)、γ-Al_(2)O_(3)组成。加入Y_(2)O_(3)后,对复合涂层中γ-Al_(2)O_(3)的生成有一定的抑制作用。随着喷涂粉末中Y_(2)O_(3)含量的增多,Al_(2)O_(3)-Y_(2)O_(3)复合涂层表面未充分熔融的颗粒逐渐增加,复合涂层的孔隙率也越来越大,掺杂了10%Y_(2)O_(3)的Al_(2)O_(3)-Y_(2)O_(3)复合涂层的孔隙率最低,涂层最致密。Al_(2)O_(3)涂层具有最高的显微硬度值(1209HV0.3)和弹性模量(227 GPa)。随着Y_(2)O_(3)含量的增加,Al_(2)O_(3)-Y_(2)O_(3)复合涂层的显微硬度与弹性模量逐渐降低。Al_(2)O_(3)-10%Y_(2)O_(3)复合涂层的弹性恢复率高达48.3%,并且其断裂韧性及抗塑性变形的能力也最好。结论掺杂了10%Y_(2)O_(3)的Al_(2)O_(3)-Y_(2)O_(3)复合涂层具有最致密的微观组织结构,其综合力学性能最好。

The work aims to investigate the effect of doping with different mass fractions of Y_(2)O_(3)on the microstructure and mechanical properties of Al_(2)O_(3)-Y_(2)O_(3)composite coatings.To achieve this objective,Al_(2)O_(3)coatings and Al_(2)O_(3)-Y_(2)O_(3)composite coatings with Y_(2)O_(3)contents of 10wt.%,20wt.%,30wt.%,and 40wt.%were produced on the surface of Q235 mild steel by atmospheric plasma spraying technique.The morphology,microstructure and elemental distribution of the powders and the different coatings were analyzed by SEM and EDS.The phase composition of the powders and coatings was analyzed by XRD.The mechanical properties of the coatings,such as microhardness,modulus of elasticity,and fracture toughness,were tested and analyzed with a microhardness tester,a nanoindentation tester and an electronic universal testing machine.The results showed that the phase composition of Al_(2)O_(3)powder wereα-Al_(2)O_(3),and the Al_(2)O_(3)phases in Al_(2)O_(3)coating and its Al_(2)O_(3)-Y_(2)O_(3)composite coating were composed ofα-Al_(2)O_(3)andγ-Al_(2)O_(3).Besides,Y_(2)O_(3)powder and coating were all composed of c-Y_(2)O_(3),but the Y_(2)O_(3)of Al_(2)O_(3)-Y_(2)O_(3)composite coating was composed of c-Y_(2)O_(3)and m-Y_(2)O_(3).The addition of Y_(2)O_(3)had a certain inhibitory effect on the generation ofγ-Al_(2)O_(3).With the increase of Y_(2)O_(3)content,the insufficiently fused particles on the surface of the Al_(2)O_(3)-Y_(2)O_(3)composite coating gradually increased,and the surface became rougher.The Al_(2)O_(3)and Y_(2)O_(3)phases in the composite coating showed a laminar distribution,and the combined interface of Al_(2)O_(3)and Y_(2)O_(3)was more dense,and the Y_(2)O_(3)in the powder was well retained in the coating.The Al_(2)O_(3)-Y_(2)O_(3)composite coating doped with 10wt.%Y_(2)O_(3)had the lowest porosity and the densest coating.When the content of Y_(2)O_(3)exceeded 10wt.%,the porosity increased with the increase of Y_(2)O_(3)content.In terms of mechanical properties,the Al_(2)O_(3)coating had the highest microhardness value(1209HV0.3).The cross-sectional microhardness was less than the surface microhardness in all coatings.The microhardness of Al_(2)O_(3)-Y_(2)O_(3)composite coatings gradually decreased with the increase of Y_(2)O_(3)content.Among them,when the doping amount of Y_(2)O_(3)in the Al_(2)O_(3)-Y_(2)O_(3)composite coating was 10wt.%,the decrease in the microhardness value compared to the Al_(2)O_(3)coating was not obvious.In the Weibull distribution image,the slope of the straight line after linear fitting of the Al_(2)O_(3)-10wt.%Y_(2)O_(3)composite coating was the largest,indicating that the coating was the densest.The results of the nanoindentation experiments showed that the Al_(2)O_(3)coating had the highest nanoindentation hardness(14.95 GPa)and elastic modulus(227 GPa).The larger the content of Y_(2)O_(3)in the composite coating,the smaller the values of nanoindentation hardness and elastic modulus.The Al_(2)O_(3)-10wt.%Y_(2)O_(3)composite coating had the best elastic recovery of 48.3%and the best resistance to plastic deformation.The results of the three-point bending experiments showed that the Al_(2)O_(3)-10wt.%Y_(2)O_(3)composite coating had the largest stress and strain values(σ=742.56 MPa,ε=3.08%)when fracture occurred,and its fracture toughness was the best.The results showed that the Al_(2)O_(3)-Y_(2)O_(3)composite coating doped with 10wt.%Y_(2)O_(3)had the densest microstructure and the best overall mechanical properties.