G.Montay
,
A.Cherouat
,
A.Nussair
,
J.Lu
材料科学技术（英文）
Residual stress in coatings is the result of individual particle stress. Their effects may be either beneficial or detrimental, depending upon the magnitude, sign and distribution of the stresses with respect to the external load. Tensile stress which exceeds the elastic limit causes cracking in surface coatings or at the interface between the substrate and the coat. Compressive stress, in general, has a beneficial effect on the fatigue life, crack propagation, coating adhesion and on the durability of the top coat during service. Compressive residual stresses can increase the number of cycles before crack initiation begins through a mean stress effect. Temperature gradients which occur during solidification and subsequent cooling are the principal mode of internal stresses generation. Some parameters influence the residual stress field of both the coating and the substrate. Substrate nature, spraying temperature, thickness of the coat layer, substrate preparation (grit blasting conditions), and velocity of the splats are in the relation with the quality of the coating. In this work, we will describe the role playing by the ceramics coating elaboration on the residual stress gradient in depth of the component. The incremental hole drilling technique has been developed to determine the residual stress gradient in depth of the coat and substrate which must be used with particularly conditions. This new technology has been employed on zirconia, alumina and tungsten carbide plasma sprayed coating.
关键词:
Coating
,
null
,
null
,
null
Na WANG
,
Chungen ZHOU
,
Shengkai GONG
材料科学技术（英文）
The nanostructured zirconia coatings were deposited by atmospherically plasma spraying. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction were used to investigate the microstructure of the zirconia coatings. Thermal diffusivity values at normal temperatures have been evaluated by laser flash technique. Effect of annealing on the microstructure evolution of the zirconia coating has been performed. The grains and thermal diffusivity are increased with increasing annealing time and temperature. The grain growth is according to the GRIGC (the grain rotation induced grain coalescence) mechanism. The increase in thermal diffusivity is attributed to the grain growth and the decrease in porosity of nanostructured zirconia coatings.
关键词:
Grain size
,
null
,
null
,
null
周亮
,
罗发
,
张勇
,
孙志平
宇航材料工艺
doi:10.3969/j.issn.1007-2330.2015.03.014
以内送粉和外送粉两种方式微弧等离子喷涂工艺制备了NiCrAlY/Al2O3复合涂层,分析了送粉方式对涂层相组成、微观结构和介电性能的影响.结果表明:与外送粉相比,内送粉方式沉积的涂层具有较高的沉积效率和较低的孔隙率.由于喷涂过程中α-Al2 O3颗粒完全熔融,内送粉喷涂所得到涂层主要为γ/γ'和γ-Al2O3相,并且涂层结构致密,NiCrAlY颗粒分布均匀.介电性能测试表明,以外送粉方式制备的涂层复介电常数实部和虚部几乎不随频率发生变化.而以内送粉方式喷涂的涂层复介电常数实部和虚部随频率的增加而降低,呈现明显的频散现象.
关键词:
送粉方式
,
等离子喷涂
,
金属陶瓷
,
介电性能
