Vickers hardness indentation size effect in selective laser melted MS1 maraging steel

In this paper, selective laser melting fabricated specimens in non-heat-treated and heat-treated conditions were subjected to Vickers microhardness testing, by using a full range of loadings: 10, 25, 50, 100, 200, 300, 500, and 1000 g. Microhardness of longitudinal sections and cross-sections were correlated and the obtained values were plotted against loadings and indentation size effect was studied, in order to find the optimal loading range, that gives the material true microhardness, or load-independent hardness. The load dependence of the measured Vickers hardness values was described quantitatively through the application of the Meyer’s law, proportional specimen resistance, and the modified proportional specimen resistance model. It was found that the microhardness rises as the loading is higher, causing a reversed indentation size effect, clearly indicating the range of true hardnesses of the tested material. Also, proportional specimen resistance and modified proportional specimen resistance models were found to have the highest correlation factors indicating their higher adequacy compared to Meyer’s prediction model.

On the Load Dependence of Micro-Hardness Measurements: Analysis of Data by Different Models and Evaluation of Measurement Errors

The influence of applied loads between 0.09807 N and 0.9807 N on measured values of micro-hardness was evaluated by Meyer’s index n, proportional specimen resistance model (PSR) and Hays – Kendall methods, Total Dispersion Zone and Analysis of Variance (ANOVA). The measurement was repeated 6 times using the same hardness reference block with standard hardness Hc= 327 HV0.05 as a sample. The influence of the load on the measured value of micro-hardness is statistically significant, and the relationship between applied load and micro-hardness manifests reverse indentation size effect (ISE) for most of “measurements”. The high value of the uncertainty of results can affect the existence and nature of ISE, especially at low loads.

THE AUTOMATIC TESTERS IN MICROHARDNESS MEASUREMENT AND ISE EFFECT

<p>The measurement of micro-hardness with applied loads 0.09807 N, 0.24518 N, 0.49035 N and 0.9807 N has been carried out by three automatic and one manually-operated micro-hardness testers. The certified reference material (CRM) was the tested sample. Each operator obtained readings of the tester which she/he normally operates. The measurement was repeated after thirty months. The influence of the testers and their stability, as well as applied load on the measured values of the micro-hardness and the indentation size phenomenon (ISE), were evaluated. The parametric and non-parametric tests, Analysis of Variance (ANOVA), Z-score and Total Dispersion Zone were used for the evaluation of the statistical significance of obtained factors. The ISE was evaluated using Meyer’s and Proportional Specimen Resistance model and also by Hays – Kendall approach. The variability of measured values of the micro-hardness values and parameters ISE is high despite the use of automatic hardness testers with practically excluding the impact of the operator. The results are affected by testers and by used testers and by applied loads. The measurement system can not be considered to be stable.</p>

Analysis of the Indentation Size Effect in the Microhardness Measurements inB6O

The Vickers microhardness measurements of boron suboxide (B6O) ceramics prepared by uniaxial hot-pressing was investigated at indentation test loads in the range from 0.10 to 2.0 kgf. Results from the investigation indicate that the measured microhardness exhibits an indentation load dependence. Based on the results, we present a comprehensive model intercomparison study of indentation size effects (ISEs) in the microhardness measurements of hot-pressed B6O discussed using existing models, that is, the classical Meyer's law, Li and Bradt's proportional specimen resistance model (PSR), the modified proportional specimen resistance model (MPSR), and Carpinteri's multifractal scaling law (MFSL). The best correlation between literature-cited load-independent Vickers microhardness values, the measured values, and applied models was achieved in the case of the MPSR and the MFSL models.

Indentation Load-Size Effect in Al2O3 — SIC Nanocomposites

Indentation Load-Size Effect in Al2O3 — SIC Nanocomposites The indentation load-size effect (ISE) in Vickers hardness of Al2O3 and Al2O3 + SiC nanocomposites has been investigated and analysed using Meyer law, proportional specimen resistance (PSR) model and modified proportional specimen resistance (MPSR) model. The strongest ISE was found for alumina. Both the PSR and MPSR models described the ISE well, but the MPSR model resulted in slightly lower true hardness values for all materials investigated. No evidence of the effect of machining stresses on the ISE has been found.

Mechanical Properties of CaF2 Single Crystal Substrates Determined from Nanoindentation Techniques

CaF2 single crystals are interesting substrate materials for deposition of thin films. Its structure is cubic and it cleaves on {111} planes. CaF2, whose hardness has been reported to be 4 on the Moh's scale, is plastic and soft. In this study, the mechanical properties such as hardness(H) and Young's modulus(E) of single crystal CaF2 mineral were measured by using a nanoindenter with a Berkovich indenter normal to (100) and (111) planes. A normal indentation size effect (ISE) in accordance with the traditional power law and the proportional specimen resistance model (PSR) of Li and Bradt [1] was observed. The values of E and H on (100) plane are larger than those on (111) plane and these values on both planes decrease with increase in time during the hold segment. The effect of displacement rate on mechanical properties of (100) and (111) surfaces is also studied.

The frictional component of the indentation size effect in low load microhardness testing

The role of friction between the microhardness indenter and the test specimen is addressed through the analysis of dry (unlubricated) and lubricated tests on iron by Atkinson and Shi. Quantitative evaluation through a proportional specimen resistance model accurately describes the results. It suggests that friction is a major portion of the observed hardness increase at low test loads, the indentation size effect. The ISE is related to the surface-area-to-volume ratio of the indentation, which is inversely related to the indentation dimension.