Investigation on the tribological properties of boron and lanthanum permeated mild steel

AISI 1045 steel was permeated with boron and co-permeated with boron and lanthanum by means of solid permeation technique. The tribological behavior of boron and lanthanum co-permeated AISI-1045 steel under dry sliding in air was investigated and compared with that of the boron permeated and tempered AISI-1045 steel specimens with a reciprocal friction and wear tester. The cross-section of the permeated and co-permeated coatings and the morphologies of the worn surface and wear debris were examined by means of scanning electron microscopy, and the chemical states of the wear debris examined by means of X-ray photoelectron spectroscopy. Then the wear mechanisms of the permeated and co-permeated layers were discussed. As the results, boron and lanthanum co-permeated specimen shows much better wear resistance than the boron permeated and tempered specimens under a load of 20 to ∼100 N and a frequency of 20 to ∼60 Hz. However, the permeation has little effect on the coefficient of friction, but liquid paraffin is significantly reducing coefficient of friction. The treated specimens contain Fe2B phase and exhibit more compact structure and higher hardness, and the corresponding wear debris is smaller than that of the tempered ones. The surface layers of the boron-permeated and the boron and lanthanum co-permeated specimens show some kind of solid lubricity and hence prevent the direct metallic contact of the frictional pair, thus the improved wear-resistance is reached. Moreover, Fe2B and B2O3 in the surface layers of the boron-permeated and boron and lanthanum co-permeation specimens restrain wear during the friction process, with the generation of iron oxide and boron oxide. This leads to wear of the specimens at extended test duration.