The Latest Research Trends and Research Results in Active Screen Plasma Nitriding

技術解説－協会賞にちなんだ技術解説・平成23年度技術賞（粉生賞）

Current Research Trends in International Conferences on Plasma Surface Engineering

報

Effect of Number of Multilayer Repetitions and Thickness Ratio on Coating Properties of Si-DLC/DLC Multilayer Coatings on Aluminum Alloys

Aluminum alloys are light and have good workability; however, their low hardness and poor wear resistance are drawbacks limiting their wide application in the automotive industry. The deposition of diamond-like carbon (DLC) films, which exhibit high hardness and good wear resistance, onto the surface of Al alloy substrates, can overcome these drawbacks. As Al alloys and DLC films have low affinity for each other, adhesion between the two is poor; adhesion can be improved by using of an interlayer. For coatings with the same thickness, film properties are improved by forming multilayer structures. In this study, the sample was formed with a uniform film thickness of 2 µm, to change the thickness ratio of the Si-DLC/DLC layer to 1:1 or 1:3 and to change the number of multilayers [Si-DLC/DLC]N to 1, 2, and 4. The samples were then tested by nanoindentation, Rockwell indentation, scratch, and wear tests. The sample with a thickness ratio of 1:1 increased the hardness and hardness/Young\u27s modulus (H/E) of the film by increasing the number of multilayers repetitions. However, for the sample with a thickness ratio of 1:3, 2 and 4 multilayer repetitions did not effect a significant difference in the hardness and H/E ratio. These samples did not improve the adhesion properties, because of no significant difference by the Rockwell indentation and scratch tests. By the wear test, samples with a 1:1 thickness ratio of the multilayer increased the delamination length and decreased the friction coefficient with increasing number of multilayers repetitions. Samples with a 1:3 thickness ratio of the multilayer increased the delamination length with increasing number of multilayers repetitions, whereas samples with 2 and 4 multilayers did not cause a significant difference in the delamination length. Moreover, the friction coefficient of the samples decreased with increasing number of multilayers repetitions. This study showed the delamination length of DLC films is proportional to increasing H/E ratio

Surface Modification of Ferritic Stainless Steel by Active Screen Plasma Nitriding

Plasma nitriding is a surface modification process with a low environmental impact. Active screen plasma nitriding (ASPN) is one of the new plasma nitriding technologies, and can eliminate problems related to conventional direct current plasma nitriding (DCPN). In this study, ferritic stainless steel SUS430 samples were treated by ASPN to increase their wear resistance without decreasing their corrosion resistance. ASPN was performed in a nitrogen-hydrogen atmosphere with 25%N2 + 75%H2 for 18 ks at 623 K, 673 K, 723 K, 773 K, and 823 K under 600 Pa using an SUS304 screen. When the sample was treated at 673 K by ASPN, the pitting corrosion resistance and wear resistance of its surface were improved because of the formation of the Sα phase and a deposited layer containing Ni on the sample surface

Low energy indium or gallium ion implantations to SiO2 thin films for development of novel catalysts

It has been demonstrated that indium (In) implanted silicon dioxide (SiO thin films catalyze a reaction of benzhydrol with acetylacetone. In this study, it is found that the threshold In ion incident energy for manifestation of the catalytic effect exists between 400 and 470 eV. Furthermore, a technique to implant gallium (Ga) to SiOfilms has been developed with highly controlled doses and injection energies for the formation of thin films that promote Ga catalysts. The efficiency of catalytic reactions by Ga implanted SiOthin films is yet to be improved. Unlike In implanted SiO2, the reason why no significant reaction was observed in the case of Ga implanted SiOfilms examined in this study seems that the Ga ion energy was so low that deposited surface Ga atoms should lack interactions with Si atoms for the manifestation of catalytic reaction. © 2014 The Surface Science Society of Japan.Satoru Yoshimura, Masato Kiuchi, Yoshihiro Nishimoto, Makoto Yasuda, Akio Baba, Satoshi Hamaguchi, Low Energy Indium or Gallium Ion Implantations to SiO2 Thin Films for Development of Novel Catalysts, e-Journal of Surface Science and Nanotechnology, 2014, Volume 12, Pages 197-202, Released April 26, 2014, Online ISSN 1348-0391, https://doi.org/10.1380/ejssnt.2014.197, https://www.jstage.jst.go.jp/article/ejssnt/12/0/12_197/_article/-char/e

Simultaneous Diffusion Coating of Cr and Si on Stainless Steel using Fluoride-Free Activator

The simultaneous deposition of chromium and silicon on stainless steel using a halide-activated diffusion coating process was performed to improve oxidation properties at high temperatures. Conventional procedure in diffusion coating process uses an activator containing fluoride. Fluoride is harmful for the human body and the environment. This experimental object is a development of the fluoride-free activator in diffusion coating of chromizing-siliconizing. In this investigation, Cr-Si intermetallic compound layers were coated on stainless steel by the pack cementation to improve its oxidation resistance and the resulting properties of the obtained coatings were investigated. The pack powders used for the diffusion coating were Cr and Si as diffusion element, Al2O3 as filler, and NH4Cl and CaCl2 as fluoride-free activator or NH4Cl, NaF and AlF3 as fluoride-added activator. The diffusion coating treatment was conducted at 1323 K for 18.0 ks in an Ar atmosphere. After the simultaneous deposition of chromium and silicon on stainless steel, a modified layer was observed on the treated sample surface and fluoride-free activator could also modify the steel surface using pack cementation