Abstract: The directionally solidified Ni3Al base alloy IC6A was coated with NiCoCrAlYHf overlay coating by vacuum arc deposition method. The microstructure of interfacial area between NiCoCrAlYHf overlay coating and substrate of alloy IC6A was investigated with scanning electron microscopy(SEM), transmission electron microscopy(TEM), energy dispersive spectrum(EDS) technique of electron probe micro-analyzer(EPMA) and X-ray diffraction technique for specimens as annealed in vacuum and after high temperature exposure. The results show that the interfacial area is consisted of deposition layer, diffusion layer and influence layer. No cracks are found in the interface between the coating and the substrate for the specimen after exposure at 1000℃ for 100h. During high temperature exposure, the width of the diffusion layer and influence layer increase slightly, the volume percentage of β-NiAl phases and α-Cr phases in deposition layer decrease, the dimension and volume fraction of the bulk shape phases formed in the influence layer increase, and the rod like or needle like δ-NiMo phases precipitate in the influence layer. The microstructure change in the interfacial area is related to the inter-diffusion of elements between the coating and the substrate.
Microstructure of interfacial area between NiCoCrAlYHf overlay coating and substrate of alloy IC6A
Abstract：
The directionally solidified Ni 3Al base alloy IC6A was coated with NiCoCrAlYHf overlay coating by vacuum arc deposition method. The microstructure of interfacial area between NiCoCrAlYHf overlay coating and substrate of alloy IC6A was investigated with scanning electron microscopy (SEM) , transmission electron microscopy (TEM) , energy dispersive spectrum (EDS) technique of electron probe micro analyzer (EPMA) and X ray diffraction technique for specimens as annealed in vacuum and after high temperature exposure. The results show that the interfacial area is consisted of deposition layer, diffusion layer and influence layer. No cracks are found in the interface between the coating and the substrate for the specimen after exposure at 1?000?℃ for 100?h. During high temperature exposure, the width of the diffusion layer and influence layer increase slightly, the volume percentage of β NiAl phases and α Cr phases in deposition layer decrease, the dimension and volume fraction of the bulk shape phases formed in the influence layer increase, and the rod like or needle like δ NiMo phases precipitate in the influence layer. The microstructure change in the interfacial area is related to the inter diffusion of elements between the coating and the substrate.
Fig.1 Microstructure (in cross-section) of NiCoCrAlYHf overlay coating as annealed in vacuum1—Mounting materials; 2—Deposition layer; 3—Diffusion layer; 4—Influence layer; 5—Substrate
图2 NiCoCrAlYHf涂层沉积层的表面X射线衍射图
Fig.2 X-ray diffraction pattern from surface of deposition layer of NiCoCrAlYHf overlay coating
Fig.3 Microstructure (in cross-section) of NiCoCrAlYHf overlay coating after exposure at 1 000 ℃ for 100 h1—Mounting materials; 2—Deposition layer; 3—Diffusion layer; 4—Influence layer; 5—Substrate
图4δ-NiMo相的透射电镜 (TEM) 明场像
Fig.4 Bright field TEM image of δ-NiMo phases
图5 1 000 ℃曝晒100 h后各元素的含量随距涂层表面距离的变化关系
Fig.5 Content of elements vs depth from surface of coating after exposure at 1 000 ℃ for 100 h (DE—Deposition layer; DI—Diffusion layer; I—Influence layer; S—Substrate)
