Abstract In this critical review, indentation hardness data obtained during the past 80 years using Vickers, Knoop, and Berkovich diamond pyramidal indenters are presented. The data show a very wide variation of values, ranging from ~60 GPa to 6000 GPa. To rationalize the data, it has been argued, using theoretical grounds, that values higher than ~230 GPa are most unlikely. Moreover, it has been emphasized that a recently reported Vickers hardness of 200 GPa for nanotwinned diamonds, and claimed as being unprecedented, has been shown to be an incorrect claim. This emphasis is made as several previous authors had reported higher Vickers hardness values. It is suggested that the most suitable indenter for measuring the indentation hardness of diamond single crystals, diamond nanopolycrystals and nanotwinned polycrystals is the Knoop indenter, as it is more robust than the other two. The most likely highest Knoop hardness values of high purity, type IIa, diamond single crystals, and ultrafine nanopolycrystals are in the range ~130 to ~145 GPa. The upper value is Meyer's hardness obtained using a Berkovich indenter. It has been suggested that the cause of the large variation in the hardness data reported in the literature is due to the difficulty in the measurement of the indentation dimensions, fracture of diamond sample and indenter tip, and the formation of unclear indentations.

中文翻译：

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金刚石单晶、纳米多晶和纳米孪晶金刚石的压痕硬度：批判性评论

摘要 在这篇批判性评论中，介绍了在过去 80 年中使用 Vickers、Knoop 和 Berkovich 金刚石金字塔压头获得的压痕硬度数据。数据显示值的变化范围非常广，范围从 ~60 GPa 到 6000 GPa。为了使数据合理化，有人认为，根据理论依据，高于 ~230 GPa 的值是最不可能的。此外，有人强调，最近报道的纳米孪晶钻石的维氏硬度为 200 GPa，并声称这是前所未有的，但已被证明是不正确的说法。之所以强调这一点，是因为之前的几位作者报告了更高的维氏硬度值。建议测量金刚石单晶、金刚石纳米多晶和纳米孪晶多晶压痕硬度最合适的压头是努氏压头，因为它比其他两个更强大。高纯度、IIa 型、金刚石单晶和超细纳米多晶的最有可能的最高努普硬度值在 ~130 至 ~145 GPa 的范围内。上限值是使用 Berkovich 压头获得的迈耶硬度。有人认为，文献报道的硬度数据差异较大的原因是压痕尺寸测量困难，金刚石样品和压头尖端断裂，形成不清晰的压痕。