Surface Mechanical Properties and Micro-Characteristics of Ti+-Implanted Fe-Cr Alloys Depending on Cr Concentrations
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SURFACE MECHANICAL PROPERTIES AND MICRO-CHARACTERISTICS OF Ti+-IMPLANTED Fe-Cr ALLOYS DEPENDING ON Cr CONCENTRATIONS
JUN SASAKI* AND MASAYA IWAKI** *Electronicsand Control Systems R & D Lab., Nippon Steel Co., 1618 Ida, Nakahara-ku,Kawasaki 211, JAPAN "**RIKEN,2-1 Hirosawa, Wako, Saitama 351, JAPAN A study has been made on surface mechanical properties of Ti+-implanted Fe-Cr alloys with various Cr concentrations. The implantation was performed in the dose range from 1 X O116to
3X1017 Ti+/cm2 at the energy of 150keV. As the Cr concentration becomes lower, the friction coefficient of implanted alloys decreases, although the increase in the surface hardness is not obvious. XPS spectra show that the implantationcaused the invation of carbon to form Fe-Cr-Ti-C metastable alloys containing chromium and iron carbides. It is concluded that Ti +-implantation
is useful for decrease in friction of Fe-Cralloys with the lower Cr concentration.
1. INTRODUCTION Titanium implantation is a useful technique for improvement of wear and corrosion of steels used for precise products, such as 52100 [1], 18W-4Cr-1V [2] and so on. Many types of such steels contain chromium with variety of concentration. This paper presents basic aspects of the surface mechanical properties of Ti +-implanted Fe-Cr alloys depending on their Cr concentrations. 2. EXPERIMENTAL Substrates used were Fe-Cr alloy plates prepared with four different Cr contents of 5, 10, 15 and 20 wt.%. The surface of each specimen was mechanically mirror-polished with diamond particles down to 0.5 pm. Implantation was 2 performed in the dose range from 1X 1016 to 3X1017 Ti+/cm at the energy of 150keV. The specimens were fixed on a heat sink block and the temperature during the implantation was kept 2at near room temperature. Beam current during implantation was lpA/cm . A part of each sample was masked by aluminium sheets in order to clarify the implantation effects on the measured properties. The Vickers hardness of the implanted specimens was measured at the load of 2gf using a micro-Vickers hardness tester. Friction measurements were carried out in atmospheric room temperature using a Bowden-Leben type friction tester. An unimplanted AISI-1045 carbon steel pin, which is in 5mm diameter and has a rubbing surface of hemispherical with radius, was slided on the specimen between implanted region and unimplanted region at the velocity of 0.04 mm/sec. without lubrication. The applied weight force was 0.245 N. Surface microcharacteristics were estimated by means of X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and scanning electron microscope (SEM). 3. RESULTS AND DISCUSSION Ti +-implantation results in the change in friction coefficient depending on the dose and the Cr concentration. Figure 1 shows the friction coefficients as a function of Cr concentration at the dose of 1X 1017 Ti+/cm 2 . The values were
Mat. Res. Soc. Symp. Proc. Vol. 100. 01988 Materials Research Society
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