Nitrogen and Carbon Solute Redistribution During High Fluence Nitrogen Implantation into Iron
- PDF / 240,106 Bytes
- 4 Pages / 420.48 x 639 pts Page_size
- 70 Downloads / 181 Views
NITROGEN AND CARBON SOLUTE REDISTRIBUTION DURING HIGH FLUENCE NITROGEN IMPLANTATION INTO IRON P.D. EHNI*, I.L. SINGER, S.M. HUES Naval Research Laboratory, Washington, DC 20375-5000, * National Research Council cooperative Post-doc
USA.
ABSTRACT Model solute distribution studies have been performed in N-implanted Fe. Concentration-verses-depth profiles have been determined by secondary ion mass 13 C at 190keV and spectroscopy for Fe implanted to low fluences with isotopes 1 5N at 180keV followed by 14 N to high fluences. At N fluences greater than 17 2 13 15 2.5 x 10 /cm dramatic changes in the C and N profiles are observed. It is proposed that these changes are caused by the lattice dilation due to precipitation of iron nitrides. INTRODUCTION High fluence ion implantation is a widely studied process for creating surface alloys with enhanced tribological properties[1,2,3]. Surface analytical studies have shown that the composition and structure of metals implanted to high fluences can be greatly influenced by phase formation and dissolution, solute redistribution, surface sputtering and lattice dilation[4]. In particular, it has been shown that implanted nitrogen atoms [5,6] and solute carbon atoms[6] redistribute as a result of high fluence N implantation into steels. To effectively utilize ion implantation, an understanding of the chemical and microstructural basis for the implantation alloying process is essential. Several models have been developed to explain the concentration profiles of N implanted into Fe or various steels. These include the model of Barnavon et.
al.[5] which accounts for sputtering and
includes a term for 'out diffusion' of the solute during implantation and the work of Farkas et. al.[7] which includes sputtering, collisional mixing, lattice dilation, thermal diffusion, and radiation-induced segregation. The present paper will examine the changes in the carbon and nitrogen profiles during high fluence nitrogen implantation into iron at room temperature. 1 A model "Fe-C-N alloy" has been created by implanting ions of rare isotope 3 C and 1 5 N to low fluence into pure Fe. Secondary ion Mass spectrometry (SIMS)1 3 was used to measure the changes in the composition vs 15 depth profiles of C and N resultiný from subsequent 1 4 N implantation. We 13 will describe the changes in C and 1N profiles in terms of dilation of the Fe lattice due to precipitate formation. EXPERIMENTAL Circular disks of Fe, 1/2" x 1/8", were implanted with C and N at the energies and fluences listed in table I. The C implantations were performed first over the entire surface. A third of the surface was then masked to provide a reference and the rest of the sample was1 4 implanted with 1 5 N. Finally, the sample was implanted with either no N, a medium fluence of 1 4 N or a high fluence of 14 N, see table I. Three sets of samples were produced. The sets were distinguished by having either shallow C implants (70keV), deep C implants (190keV), or both shallow and deep C implants. The energy for N implantations (180keV) w
Data Loading...
