雾化气体对热喷涂NiCr涂层弹性模量的影响

Effect of Atomization Gases on the Elastic Modulus of Thermal-sprayed NiCr Coatings

摘要:

准确评价热喷涂涂层的弹性模量对于确保工业构件的服役安全性与耐久性是十分重要的，但是利用传统技术很难进行评价。尽管纳米压痕技术可以表征涂层局部的弹性模量，但是无法反映出孔隙、裂纹等缺陷对涂层弹性模量的影响。而脉冲激励技术（IET）是一种用于评价块体材料弹性模量的简单、准确方法。本文结合相对法，利用IET可对热喷涂涂层的弹性模量进行评价。首先构建了涂层、基体、涂层/基体复合体系的弹性模量间的解析关系，然后通过测量制备涂层前后试样的弹性模量，即可获得涂层的弹性模量。以Q235钢基体/NiCr涂层为研究对象，研究了雾化气体对NiCr涂层弹性模量的影响。结果表明以空气作为雾化气体制得的NiCr涂层（NiCr-Air）的弹性模量高于以N2作为雾化气体制得的NiCr涂层（NiCr-N2）的弹性模量，其原因在于NiCr-Air中形成了Ni(Cr2O4)氧化物增强NiCr合金的层状复合材料，且这种层状复合结构有利于提高NiCr涂层的弹性模量。

Abstract:

Accurate evaluation of the elastic modulus of thermal-sprayed coatings is very important to ensure the safety and durability of industrial components, but it seems difficult via conventional technique. Although indentation technique is available to estimate the local modulus of coatings, it does not reflect the effects of porosity or cracks. Impulse excitation technology (IET) is a simple and accurate method to evaluate the elastic modulus of bulk materials. It was used to determine the modulus of thermal-sprayed coatings via relative method in this work. An analytical relationship among the moduli of the coating, the substrate and the coating/substrate system was derived. Thus, the modulus of coatings was obtained via the measured modulus of the samples before and after coating. Experiments on Q235 steels coated with NiCr coatings, were carried out to investigate the effect of atomization gases on the elastic modulus of NiCr coatings. The results indicated that the elastic modulus of NiCr coating prepared by air atomization (NiCr-Air) was higher than that of NiCr coating prepared by N2 gas atomization (NiCr-N2). The reasons for this were the formation of Ni(Cr2O4) reinforced NiCr alloy laminated composite, and the laminated composite structure had a positive influence on the elastic modulus.