Wear of steels implanted with oxygen or aluminium ions in air, oxygen and nitrogen

Abstract

The wear resistance of the martensitic steels AISI 52100 and 440B improved by a factor of more than two by implantation of aluminium ions, and by up to two orders of magnitude after implantation of oxygen ions or co-implantation of aluminium and oxygen ions when tested with a ball-on-disc tribometer in air. Wear tests of oxygen-implanted samples in dry oxygen and dry nitrogen proved the importance of air humidity for the tribo-oxidation of iron. The wear behaviour of the co-implanted samples was less determined by air humidity than that of the oxygen-implanted samples. Instead, the wear reduction of the co-implanted samples depended on the oxygen content of the test atmosphere. Measurements of the microhardness indicated the formation of iron oxides after oxygen implantation and of aluminum oxides after co-implantation. The wear particles formed on AISI 52100 in air contained FeOOH before implantation and both FeOOH and Fe 2O 3 after all types of ion implantation, as determined by infrared spectroscopy. Concentrations profiles by secondary ion mass spectroscopy (SIMS) showed a maximum of 60 at% oxygen after oxygen implantation and of 24 at% alluminium and 21 at% oxygen after co-implantation. Surface analysis of oxygen-implanted samples by X-ray photoelectron spectroscopy (XPS) showed the formation of Fe 2O 3 and Cr 2O 3 on the wear tracks. No changes in the microstructure were found by transmission electron microscopy (TEM).