Takumi Sone

Boriding of nickel by the powder-pack method

Abstract Boriding of nickel (Ni) has been performed by means of a powder-pack method using boriding powder that contains no silicon. In this study, the boride layer was analyzed with an X-ray diffractometer and electron probe microanalyzer (EPMA). We studied the high-temperature hardness and the friction and wear characteristics of the layer. The results showed that the boride layer was composed of Ni 2 B and that the high-temperature hardness of borided Ni was higher than that of untreated Ni. The friction and wear properties of Ni were improved by boriding.

Friction and wear of DLC films on 304 austenitic stainless steel in corrosive solutions

Abstract Diamond-like carbon (DLC) films are well known for their high hardness, low friction and excellent wear resistance. In the present work, the friction coefficient and wear resistance of DLC films deposited on 304 austenitic stainless steel were investigated in corrosive solutions. DLC films were deposited on the substrate by the CVD method using radio frequency (13.56 MHz) plasma. A mixture of methane (CH4) and hydrogen (H2) was used as processing gas. The CH4 concentration was varied from 20 to 100%. DLC films were subjected to friction and wear tests using a ball-on-flat surface friction apparatus in solutions of 3 mass% NaCl, 0.05 N HCl, 0.05 N H2SO4 and 0.05 N HNO3. The flat surface was oscillated against the alumina ball. In the tests performed within the corrosive solution, the friction coefficients of the DLC films and substrate were approximately 0.1 and 0.5, respectively. The DLC films deposited on the 304 substrate showed a remarkably lower volume of wear than the substrate alone. Accordingly, the DLC coating process was confirmed to be effective in decreasing the friction coefficient and improving the corrosion wear resistance of 304 in 3 mass% NaCl and acidic solutions.

Surface Layer Hardness of Austenitic Stainless Steel via Low Temperature Plasma Carburizing and/or Nitriding

Surface layer hardness and concentration profiles of austenitic stainless steels after plasma carburizing and /or nitriding at 673 K were investigated. Carbon and nitrogen concentration were measured by glow discharge optical emission spectrometry (GDOES) and carbides or nitrides were detected by x-ray diffraction analysis (XRD) and TEM. The state of carbon at the treated surface was investigated by Raman spectroscopy. Separation of carburized layer and nitrided layer was observed in a simultaneous carburizing and nitriding plasma treatment.

Boriding of Nickel in Fluidized Bed

Bonding is useful in surface hardening nickel (Ni) in many surface treatments. Although Ni boronized by powder-pack bonding with amorphous boron and by gas bonding with BCl3 has been reported, few reports cover bonding in a fluidized bed. We analyzed the treated layer using X-ray diffraction (XRD), glancing incidence X-ray diffraction, glow discharge emission spectrometry (GDS), and electron probe microanalyzer (EPMA). High-temperature microhardness and friction and wear characteristics of boronized Ni were studied, with the following results:(1) Bonding Ni at a high temperature over a long time in a fluidized bed showed flaking of the treated layer due to Ni siliconization.(2) The Knoop hardness was 1300HK for the sample boronized 7.2ks at 1073K. The boride layer was about 25μm thick and consisted mainly of Ni2B and Ni3B.(3) The high-temperature microhardness of boronized Ni is higher than that of untreated Ni below about 800K.(4) Friction properties and wear resistance to SUJ2 and SUS304 were improved by Ni bonding.