In the field of Cold pressing and Hot stamping, the issue exists in the situation where the effective of PVD coated metal mold is not enough due to severe usage environment. The present study puts its focus on the friction behavior occurred by each PVD coating and the phenomena worked on each coating surface during sliding. Consequently, it provides that Vanadium based nitride coating have an advantage over other nitride coating regarding friction properties. As for DLC-based coating, it is indicated that there is possibility to use practically at usage environment at 400 degrees as Hot stamping application.

To a mold for powder and resin molding, mold release characteristics and corrosion resistance are required in addition to wear resistance. The surface treatment that included all these characteristics is limited. Therefore, a new surface finishing continues being developed. This report comments on a prediction of the nitride film having high mold release property using first principles calculation, a modification of the film structure in the cathodic arc ion plating process and the pretreatment for PVD coating onto cold working die steel corresponding to SKD11 by the electron beam irradiation in order to improving the adhesion and the corrosion resistance.

The coating methods and characteristics of the latest DLC coating for die and mold are explained. Ta-C film is deposited by cathodic arc deposition and is suitable for die and mold coating. By applying ta-C film, it is possible not only to extend the life of the die and mold and reduce maintenance work, but also to reduce lubricants such as oil. The latest filtered arc deposition to decrease the surface roughness of ta-C film is also introduced.

The facing dual-beam arc deposition (FDAD) method is developed in order to form uniform TiN film on the deep hole surface in dies, in which dual beams of Ti⁺ and N₂are irradiated from the both sides of a long through-hole. This innovative coating method makes it possible to form TiN film on the whole inner surface of a hole, which has an aspect ratio of 108L/20D=5.4, with a uniform film thickness, film hardness and film composition close to a stoichiometry ratio.

Glass lens molds are required to have strength and oxidation resistance characteristics at 600°C or higher. As a mold material that meets these required performances, there is a SiC mold, which has produced a great effect. This article introduces the characteristics of SiC bulk molds produced by the CVD method and explains the prospects for glass lens molds.

In this paper, we have focused on the recent progress both in hard coatings useful for surface treatment of molds and in their processing based on dry coating technology. First, the new developments in the application of hard coatings to molds were described, focusing on the results of a recent literature survey. In addition, regarding the progress of the processing technology itself, we have introduced what we think will contribute to the development of mold coating technology in the future. Specifically, we introduced small volume high-speed coating, local ultra-high-speed coating, and surface hardening treatment based on high-density plasma generation technology. In particular, local processing is expected to match when hard surfrace is required only on a portion of the mold rather than the entire surface of it. Finally, the progress of dry coaitng technology on the inner surface was explained. This is because a mold typically has many inner surface shapes.

Following the previous paper focusing on tribological properties of HFO (hydro fluoro olefin) refrigerant, the adsorption behavior of refrigerants on the nascent iron surface was investigated experimentally and the adsorption structure, adsorption energy and dynamic process of chemical reaction of refrigerants were analyzed by a molecular simulation. The adsorption behavior on the nascent iron surface was highly dependent on the molecular structure of the refrigerant. HFO refrigerants with an unsaturated bond exhibited high adsorption activity, and halogen species also affected the adsorption activity. HFO showed higher adsorption activity than organic ester, phosphate ester and alkyl sulfide as model compounds of refrigerator oil. In adsorption simulation by neural network potential (NNP), HFO molecules showed large negative adsorption energy. To understand the mechanism for this stronger adsorption of HFO species, density functional theory calculation was conducted, and it showed that HFO adsorbs on iron surface by electron donation from the molecule and back-donation from iron surface. There was also a good correlation between the experimental adsorption activity and the NNP-obtained adsorption energy. MD simulation of molecule adsorbed on the nascent surface at temperature of 298 K was subsequently done using NNP technique. The results showed that CF₃CF = CH₂ (R1234yf) exhibits a distinct decomposition reaction with releasing F atoms and it generates several Fe-F bonds, meaning that precursor of iron fluorides forms on the surface. It is worthy to mention that a formation of the iron fluoride has been experimentally detected on friction track by using XPS in the first report of this study. It was concluded that the adsorption and tribochemical formation of iron fluoride from HFO are supported by molecular simulation performed in this study.

Hydrophobicity and sliding behavior of a water drop are very important phenomena in our daily life as well as in many industrial processes. However, the difference between these two phenomena is not well understood. This study was performed to investigate the movement of the water drops on the inclined surfaces of the silicone films and was focused on the friction force between the water drops and the inclined surfaces. Using a high-speed camera system to observe the sliding movement of the water drops, the sliding speed of the water drops under the various tilt angles and the various drop volumes was investigated. The sliding speed of the water drops increased with increasing the tilt angle and the drop volume. Equation of motion was used to calculate the friction force from the sliding movement. The friction force was proportional to the power of the terminal sliding speed. It was clarified that the main cause of the friction force was the surface tension, and the secondary cause was the viscous resistance. This result is expected to contribute the prediction of the sliding behavior of water drops.