Mo_２NiB_２－Ni cermets have been studied by substituting transition metals to the metal site of Mo_２NiB_２ phase aiming to enhance their mechanical properties. However, the relationships between crystal structure and mechanical properties still have been uncleared. In this study, we investigated the nano-submicron hardness of Cr- and V-substituted Mo_２NiB_２－Ni cermets using nano-indentation and First-principles calculations to evaluate the chemical bonding in the Mo_２NiB_２ phase. Nano-indentation results eveal significantly higher hardness in the tet-Mo_２NiB_２ phase than ort-Mo_２NiB_２ one. These results are good consistent with crystal orbital Hamilton population (COHP) analysis and integrated crystal orbital Hamilton population (ICOHP) values calculated by first-principles calculations.

The swing angle of a Herbert pendulum is detected using the non-contact displacement sensors installed outside the pendulum when the hardness test is carried out with a current Herbert hardness tester. To obtain the hardness, the experimental data must be analyzed with a personal computer. Hence, the current tester has low portability. In this study, the stand-alone type Herbert hardness tester is developed by installing an accelerometer for detecting the swing angle and a microcomputer for calculating the hardness are installed on the pendulum. The hardness tests were carried out to 10 kinds of specimens to investigate the availability of the tester. The free decay curves were smooth. The correlation of the data obtained from developed and current testers was extremely strong. The reasonable evaluations of hardness with improved ease of operation can be obtained from the hardness tests with the developed tester.