3Cr13钢表面氟盐浴TD法VC涂层的制备及表征

Preparation and Characterization of Vanadium Carbide Coating on 3Cr13 Steel by Thermal Diffusion Process with Fluoride Salt Bath

采用FLiNaK氟化盐对3Cr13不锈钢表面分别进行不同时间的热反应沉积(TD),利用X射线衍射仪(XRD)、电子探针(EPMA)、扫描电镜(SEM)、显微维氏硬度计研究了VC涂层的形貌、成分特征、表面硬度及其生长动力学。结果发现,3Cr13不锈钢的表面形成了3~5μm厚的均匀致密的VC涂层,表面呈花瓣状,VC相中含少量的Si和Fe元素。VC涂层的平均(HV)硬度高达32 220 MPa,其厚度与保温时间满足抛物线关系。VC涂层表面几百纳米厚度存在不均匀分布的SiO_2,表面呈龟裂状。主要是因为SiO_2的热膨胀系数大于VC涂层,使得SiO_2在冷却过程中受到拉应力而发生龟裂。本研究首次表明低熔点高活性的氟化盐可以用于TD法制备VC涂层。

Vanadium carbide（VC） coatings were prepared on 3Cr13 stainless steel using FLiNaK salts through thermal diffusion carbide coating process（TD） for different time. The morphology, composition, hardness and growth kinetics of the VC coatings were investigated by scanning electron microscope（SEM）, X-ray diffractometer（XRD）, Vickers indenter, electronic probe microanalysis（EPMA） and energy dispersive X-ray spectrometry（EDX）. Results show that the VC coatings of 3~5 μm in thickness form on the surface of 3Cr13 stainless steel. The coatings are petal-shaped and contain traces of Si and Fe. The average hardness of the VC coating is up to 32220 MPa and there is a parabola relationship between the thickness of the coatings and the treatment time. VC coatings are covered by rimous SiO_2 phases with the thickness of hundreds of nanometers. The cracks of SiO_2 phases result from the tensile stress during the cooling process, which derive from the different thermal expansivity between VC coating and SiO_2 phase. The present study also indicates the potential application of FLiNaK salts in TD process.