Long-Range Effect of Ion-Implanted Materials in Tribological Investigations

Microhardness results and the occurrence of radiation defects at a greater depth than the predicted implanted ion range indicate the presence of the so-called long-range effect. An attempt is made to determine the thickness of a layer with modified tribological properties by measuring friction and wear factors. Tribological tests are performed on the pin-on-disc stand. The real thickness of a layer with implantation-modified tribological properties can be determined via tribological testing by measuring the wear trace depth when the friction factor and/or wear of the implanted sample is close to that characteristic of an unimplanted sample. The predicted range of the implanted ions is estimated by the SRIM and SATVAL programs. The presence of the long-range effect is confirmed for the steel grades AISI 316L, H11, Raex 400, Hardox 450 as well as for the Stellite 6 and Ti6A14V alloys. The modified layer thickness determined by tribological testing is considerably greater (4.7 divided by 16.7 times) than the initial range of the implanted nitrogen ions. The observed depth of changes in the tribological properties of the surface layer (due to the long-range effect) is consistent with the nanohardness results obtained for the steel grades AISI 316 and H11. An analysis of the content of elements on the sample surface as well as in its wear trace and wear products is performed by X-ray spectroscopy (EDS and WDXS). The results demonstrate that one of the causes of the long-range effect is the diffusion of nitrogen and carbon atoms in the friction zone during the tribological test.