What are the effects of the load time on the Vickers hardness tester?

Taiwan Nakazawa Co., Ltd. answers for you: The load should be applied smoothly and slowly, without any vibration or shock phenomena.
(1) A faster loading speed will lead to lower hardness values because the plastic deformation produced at this time is not only the static indentation of the load, but also involves a partial dynamic force, which generates kinetic energy and results in greater material deformation. This influence increases as the load decreases, the hardness range of the test specimen increases, and the mass of the moving parts in the loading mechanism increases.
(2) The loading speed should also not be too slow. Excessively prolonging the indenter's indentation time, especially when the dwell time is short, will result in the load not being maintained for the specified duration, thereby creating new deviations.
(3) A loading speed that is too slow is also susceptible to interference from external conditions. Generally, it must not exceed 50 μm/s. Based on the regulations of standard test methods from various countries worldwide, loading speeds are mostly within the range of 15-70 μm/s. The loading speed must be determined according to the loading method and the characteristics of the loading mechanism; in some cases, it is determined by the turning time of the loading handle. Regardless of the form, the necessary condition must be met: the loading speed should reach a point where it does not affect the increase in indentation size.