Improvement of hardness and wear resistance of (TiC, TiB)/Ti-6Al-4V surface-alloyed materials fabricated by high-energy
- PDF / 2,096,486 Bytes
- 11 Pages / 606.24 x 786.144 pts Page_size
- 1 Downloads / 270 Views
6/10/03
11:38 AM
Page 1461
Improvement of Hardness and Wear Resistance of (TiC, TiB)/Ti-6Al-4V Surface-Alloyed Materials Fabricated by High-Energy Electron-Beam Irradiation CHANG SUP LEE, JUN CHEOL OH, and SUNGHAK LEE The objective of this study is to investigate microstructure, hardness, and wear properties of three kinds of (TiC,TiB)/Ti-6Al-4V surface-alloyed materials fabricated by high-energy electron-beam irradiation. The mixtures of Ti C, TiC TiB2, and Ti B4C powders and CaF2 flux were deposited on a Ti-6A1-4V substrate, and then high-energy electron beam was irradiated on these mixtures. The surface-alloyed layers of 0.9 to 1.6 mm in thickness were homogeneously formed, and contained a large amount (30 to 44 vol. pct) of hard precipitates such as TiC and TiB in the martensitic matrix. This microstructural modification improved the hardness and wear resistance of the surface-alloyed layer 2 times and 6 to 9 times, respectively, greater than that of the substrate. Particularly, the surface-alloyed material fabricated with Ti B4C powders had a larger volume fraction of TiB and TiC homogeneously distributed in the martensitic matrix, and thus showed the best hardness and wear resistance. These findings suggested that the surface-alloying using high-energy electron-beam irradiation was economical and useful for the development of titanium-base surface-alloyed materials with improved hardness and wear properties.
I. INTRODUCTION
THE Ti-6A1-4V alloys have many attractive properties such as high specific strength, stiffness, and excellent corrosion resistance that have made them attractive for use in structural and engine parts of ultrasonic airplanes, materials for petrochemical plants, and surgical implants.[1,2,3] However, their poor resistance to wear at room temperature and oxidation at high temperatures have required surface treatments.[4,5,6] Thus, studies on the development of new advanced materials whose surface properties are enhanced have been conducted to achieve surface hardening or surface alloying.[7–10] Surface alloying is a method for forming an alloyed layer on a substrate to improve the resistance to corrosion, wear, and heat. Recently, this has been developed by direct irradiation using high-energy heat sources such as pulsed laser or electron beam.[11–16] The laser beam method requires absorption materials to increase the absorption ratio, and has overlapping problems when a large surface area needs to be treated. The conventional electron-beam method has been mainly applied to welding of relatively small parts because it requires a vacuum chamber. However, the high-energy (several MeV energy range) electron-beam irradiation method can be continuously performed in air,[17] and thus can treat a very large area at one time, which makes it advantageous for the fabrication of large structures or parts. Compared with the laser beam method, this method has 2 times higher ther-
mal efficiency and produces a thicker surface-alloyed layer of several millimeters in thickness,[17] due to pene
Data Loading...
