A STUDY OF DUAL CHROMIUM PLUS CARBON ION-IMPLANTATION INTO HIGH-SPEED STEEL

A large volume of data is now available on the implantation of nitrogen ions into a wide range of steels and other materials such as titanium alloys. In some cases, especially when the substrate steel materials consist of hard martensitic structures, the benefits of nitrogen implantation are less significant. A combination of titanium plus carbon ions has often been reported to produce a significant improvement in the tribological properties of bearing and high speed steels. This work reports on dual ion implantation of chromium plus carbon ions into an AISI M3:2 high speed steel, comparing the results with a titanium plus carbon implantation procedure. Implantations were carried out in a high current Danfysik ion implanter on surface ground and polished discs at doses above 10(17) ions cm-2 and energies ranging from 40 to about 180 keV to yield selected concentration profiles. Ultramicrohardness tests using a dynamic microprobe, and friction and wear testing, were carried out to evaluate the mechanical properties produced by the treatment. It is shown that this implantation procedure can yield a hardening of up to a factor of 1.2 for the highest carbon dose, this effect is very similar to that observed on multiple energy nitrogen implantation to a combined dose of up to 5.5 x 10(17) ions cm-2. The results of friction testing also indicate that a relatively significant reduction from about 0.65 to 0.5 is observed in the coefficient of friction under the conditions investigated. X-ray photoelectron spectroscopy analyses indicated that the chromium and carbon implanted elements can combine forming carbidic bonds, and when the carbon dose is increased the underlying C ls spectra show carbidic and graphitic bonds.