The research goal is to develop a new coating thin film for machining tools. The difficult – to cut materials have an excellent characteristic and are highly demanded by industry, however there are serious issue on environment load owing to their low processing efficiency. TiB2 thin film has a potential to decrease friction coefficient at elevated temperature, and we aimed to study decrease of friction coefficient under 0.1 at 600°C. In the previous research, it was found that the friction coefficient of TiB2-MoS2 composite thin film showed 0.01 at 200°C. It is considered that this ultra-low-friction characteristic is caused by tribo-chemical reaction relating with boron. This low friction property was kept even after heat treatment at 400°C. However, the friction coefficient was increased at 500°C , and the boron and sulfur contents at the TiB2-MoS2 composite thin film decreased. A new TiB2-MoS2 composite film enhances boron reaction due to excess addition of boron. As a result, it was found that boron was indispensable for the ultra-low-friction characteristic at elevated temperature because it is maintained after the heat treatment at 500°C.
In recent years, the use of ferritic stainless steel and a Ni-based brazing foil has been required in an environment where low cost and high quality are required at the same time. However, when brazing stainless steel and brazing foil, the formation of Cr–B intermetallic compounds and a Cr depletion zone were confirmed, and there was concern that the corrosion resistance around the brazed layer would decrease. Therefore, the brazing times of SUS444 / MBF20® brazed joint with excellent corrosion resistance were compared at 5 minutes, 1 hour, and 3 hours using the corrosion resistance evaluation by electrochemical method and the microstructure observation by EPMA analysis. From the results of the polarization curve, the corrosion resistance at the brazing time of 3 hours was the best. Results of microstructure observation, it was confirmed that the formation of the Cr-depletion zone was suppressed when the brazing time was 1 hour and 3 hours. From these results, it was suggested that good corrosion resistance of the brazed joint was obtained by long time brazing. These results provide new insights in determining future brazing conditions.
Recently, atmospheric carbon dioxide concentration, which may enhance on-going global warming issue, is increasing rapidly. Here, methanation of atmospheric CO2 has been suggested. However, in the methanation process developed so far, at least 200-300 °C is required with using catalysts like Ni. Therefore, it is desirable to reduce the reaction temperature by different processes from the viewpoint of energy saving and also to avoid deactivation of catalysts at high temperatures. We have recently reported that mechanochemical process of La-Ni based alloys under the presence of CO2 and H2 generates CH4 successfully. But, it has also been suggested by Atom Probe Tomography (APT) analysis carried out in this study, that CO2 might have partially reacted with the LaNi5 powder in the course of ball-milling, yielding different La-oxides, carboxides and hydrocarboxylic species containing La embedded in Ni matrix. These compounds might have acted as effective intermediate phases for the methanation reaction.
In order to elucidate the origin of the catalytic activity, in-situ monitoring of the pressure change during the process is necessary; reactivity of CO2 with LaNi5 in the said process should be investigated as well. Herein, monitoring results of mechanochemical methanation reaction by using vibrational ball-mill are presented.