Modeling of High Fluence Titanium Ion Implantation and Vacuum Carburization in Steel
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MODELING OF HIGH FLUENCE TITANIUM ION IMPLANTATION AND VACUUM CARBURIZATION IN STEEL D. Farkas , I. L. Singer , and M. Rangaswamy *Department of Materials Engineering, VPI & SU, Blacksburg,VA 24061 **Chemistry Division, Code 6170, Naval Research Laboratory, Washington, DC 20375. ABSTRACT Concentration vs. depth profiles have been calculated A computer for Ti and C in 52100 Ti-implanted steel. formalism was developed to account for diffusion and mixing A processes, as well as sputtering and lattice dilation. Gaussian distribution of Ti was assumed to be incorporated at each time interval. The effects of sputtering and lattice dilation were then included by means of an appropriate C was assumed to be gettered coordinate transformation. from the vacuum system in a one-to-one ratio with the Both Ti surface Ti concentration up to a saturation point. A series of experimental and C were allowed to diffuse. (Auger) concentration vs. depth profiles of Ti implanted steel were analyzed using the above-mentioned assumptions. A best fit procedure for these curves yielded information on the values of the sputtering yield, range and straggling, as well as the mixing processes that occur during the values are in excellent implantation. The observed agreement with the values predicted by existing theories. INTRODUCTION 17 2 Ions implanted to high fluences (> 10 /cm ) in metals are capable of creating unique alloys with remarkable mechanical and chemical properties. An example of such an alloy is the wear-resistant amorphous layer formed This layer forms by adsorbing when Ti is implanted into 52100 steel (1). carbon from residual gases in the vacuum chamber (2), assisted by Ti atoms which reach the surface by sputter erosion during implantation. The present paper describes a computational method for modeling high fluence implantation and presents calculated Ti and C depth profiles which mimic those observed for the above mentioned Ti implantation into 52100 steel. The model accounts for ion collection, sputtering and lattice dilation in a manner similar to the earlier treatments by Schultz and Wittmaak (3) and Krautle (4). It also considers the diffusion-like transport processes which affect the shape of the evolving profiles and incorporates the vacuum carburization process elucidated by Singer (2). The formalism is based on a numerical solution of the coupled diffusion equations for implanted Ti and adsorbed C. Effective diffusivities for the two species and sputtering yield by Ti ions were obtained by comparison of the calculated and experimental profiles. The experimental data modeled in the present work were obtained by Singer
(2)
THEORETICAL CONSIDERATIONS The profile of Ti implanted to high fluences processes: o Ion collection, with a Gaussian distribution
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Mat. Res. Soc. Symp.Proc. Vol. 27 (1984) OElsevier science Publishing Co., Inc.
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"o Sputter erosion of the surface "o Lattice dilation as a result of ion collection "o Diffusion-like broadening resulting from the
collision cascades or radia
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