制样方法对钢铁材料纳米压痕测试的影响

为了研究制样方法对钢铁材料纳米压痕试验结果的影响,选取单相、多相、低碳、中碳和高碳等不同类型的钢种,分别进行了纳米压痕样品制备参数的探索。利用机械磨抛和电解抛光设备进行了样品表面抛光处理,比较了氧化物机械抛光及不同参数的电解抛光对样品表面状态的影响,通过真彩共聚焦扫描显微镜定量测定了样品表面粗糙度。随后,为检验样品制备的效果,利用纳米压痕仪分别测试了两种抛光方式得到的不同组织的纳米硬度和弹性模量。结果表明,氧化物机械抛光适合制备单相且试验压入深度超过500nm的样品;电解抛光能有效避免表面硬化层,在参数适当的条件下,既可以满足测试标准的要求,又可以进行多相区分,但是,电解参数不当时会导致组织假象,严重影响测试结果的准确性。同时,对制样效果的评价应考虑试验曲线的稳定性而不仅仅注重抛光样品的平均表面粗糙度。最后,给出了适用于低碳钢W1300、中碳钢SWRCH35K和高碳钢SWRH82B的电解抛光参数,可为类似钢铁材料纳米压痕测试样品的制备提供参考和借鉴。

Effect of sample preparation method on nanoindentation test of steel

In order to study the effect of sample preparation method on the results of nanoindentation test of steel, single-phase, multiphase, low-carbon, medium-carbon and high-carbon steels were selected to explore the parameters of sample preparation of nanoindentation. The equipment of mechanical polishing and electropolishing were utilized for surface polishing, and the influence on surface condition between oxide mechanical polishing and electropolishing with different parameters was compared. The surface roughness of the sample was quantitatively determined by real color confocal scanning microscope. Subsequently, in order to verify the effect of sample preparation, a nanoindenter was employed to obtain nanohardness and elastic modulus of different microstructures by two polishing methods. The results show that oxide mechanical polishing is suitable for preparing the sample of single-phase and indentation depth more than 500nm. Electropolishing can effectively avoid the surface hardened layer. Under the appropriate parameters, it can not only meet the requirements of test standard but also distinguish different phases. However, inappropriate parameters can bring about the illusion of microstructures, seriously affecting the accuracy of the nanoindentation results. Meanwhile, the evaluation of the sample preparation should take into account the stability of the test curve rather than just the average surface roughness of the polished sample. Finally, the parameters of electropolishing for low-carbon steel W1300, medium-carbon steel SWRCH35K and high-carbon steel SWRH82B were given, which could provide reference and guidance for preparing the similar steel sample to perform nanoindentation test.