Effect of Titanium Implantation on the Mechanical Properties of Silicon Nitride
- PDF / 521,911 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 11 Downloads / 200 Views
1. INTRODUCTION Silicon nitride (Si N4 ) is one of the attractive materials because of its high strength at high temperatures, good thermal shock resistance, and excellent corrosion and erosion resistance. However, there are significant technical barriers to its widespread commercial use as a structural material. One of major problems is considered to be its brittleness; in general, the ceramic materials are sensitive to surface cracking induced by mechanical contact events, and easily and/or
suddenly fail. From such a surface sensitivity, it is expected that the mechanical properties of ceramics can be improved by surface modifications.
Ion implantation has been used to alter the surface properties of materials as a low-temperature modification technique; i.e., it can improve the wear and corrosion resistance. Especially, Til-implantation plays an important role in the improvement of the mechanical properties of steels used for precise products [1,2]. It has also been proposed that ion implantation is an effective technique for modification of surface layers of ceramic materials [3-6]. However, a few investigations have been made on the friction and wear properties of ion-implanted ceramics in contact with steels [7]. In this article, we report the effect of Ti÷-implantation on the near surface hardness, and fric-
tion and wear properties of Si 3N4 in contact with steels. To characterize such mechanical properties induced by Ti -implantation, the depth dependence of atomic fraction and chemical bonding states are analyzed by X-ray photoelectron spectroscopy (XPS) combined with Ar' sputtering. 2. EXPERIMENTAL PROCEDURE The substrate used was polycrystalline sintered Si3N4 containing 6.0 mol% AlO3 and 6.0 MOM% "Y203as sintering aids, whose surface waspolished to a mirror finish. Impian~tation of 48 Ti' was performed with doses of 1x1015 , 1x10 and 1x10 1 ' ions cm-2 at an energy of 150
keV. To suppress heating by ion bombardment, the beam current density was limited to 1.0 [LA cm- 2 . 249 Mat. Res. Soc. Symp. Proc. Vol. 354 @1995 Materials Research Society
The depth dependence of atomic fraction and chemical bonding states of Tit-implanted layers was estimated by X-ray photoelectron spectroscopy (XPS) combined with Ar' sputtering. The photoelectron ejection from the specimens was induced by 10 kV, 20 mA AlKci radiation under a pressure of less than 5x10-6 Pa. The energy scale of the spectrometer was calibrated by setting the measured Au4f7. line equal to 83.8 eV. The atomic fraction at each depth was observed from the areas of Si2p, Nis, Ti2p, Ols and Cls spectra subtracting the background by Shirley's method, by using conventional sensitivity factors. The near-surface hardness was determined by the Vickers indentation measurements, in which the normal load and dwell time applied were 100-1000 gf and 60 s, respectively. The friction and wear tests were carried out at an ambient atmosphere of relative humidity of 4050% without lubricant and at room temperature, using a pin on disk-plane and block on wheelperiph
Data Loading...
