纳米陶瓷等离子喷涂层硬度的Weibull分布及与涂层组构的对应特性

等离子喷涂层的硬度是反映其耐磨性、强度、使用寿命的重要指标,它与涂层的组构有对应的关系,但其测定结果分散性较大。为了精确测量陶瓷等离子喷涂层的硬度,在NiCrAl合金表面等离子喷涂制备了Al2O3-13%TiO2(AT13)纳米陶瓷涂层(ncc)和对照用微米涂层(mcc),采用显微硬度测试仪测量了其显微硬度,研究了其Weibull分布特性,通过SEM、XRD等分析了ncc涂层显微硬度与微观组织结构的关系,并通过TEM对涂层的微区结构进行了表征。结果表明:ncc涂层的平均显微硬度显著高于mcc,且呈双态分布;两者硬度的Weibull分布呈分散性,但ncc涂层的分布较均匀,微裂纹细小且粒径小,以α-Al2O3和γ-Al2O3及少量金红石型TiO2为主要物相;ncc涂层具有优异的力学性能主要归因于其组织的晶粒细化、纳米TiO2颗粒镶嵌于Al2O3孔隙中、Al2O3微晶弥散分布、微裂纹韧化等。

Weibull Distribution of Microhardness of Plasma Sprayed Nanostructured Ceramic Coating and Relation between Phase Composition and Microhardness

Al2O3-13%TiO2(AT13) nanostructured ceramic coating and relevant micro-sized ceramic coating for comparative study were prepared on the surface of NiCrAl alloy by plasma spraying.A microhardness meter was performed to mea-sure the microhardness of as-prepared nanostructured and micro-sized AT13 ceramic coatings,and the Weibull distribution feature of the two kinds of ceramic coatings were examined.Moreover,the phase composition of the nanostructured ceramic coating was analyzed by X-ray diffraction,and its microstructure was observed with a transmission electron microscope.It was found that nanostructured AT13 ceramic coating had much higher microhardness than the micro-sized counterpart coating,and was dominated by duplex microstructure distribution.The Weibull distribution of the microhardness of both coatings was dominated by apparent scattering,but the nanostructured ceramic coating had more evenly distributed microhardness.Moreover,nanostructured AT13 ceramic coating,consisting of α-Al2O3 and γ-Al2O3 as well as a small amount of rutile TiO2,contained tiny micro-cracks and had a small grain size.The excellent mechanical properties of nanostructured AT13 ceramic coating were mainly attributed to grain refinement,embedding of TiO2 nanoparticles in the pores of Al2O3,dispersive distribution of Al2O3 micro-crystal,and toughening of micro-cracks.