Tribological Properties of Mo-Si-B Alloys Doped with La2O3 and Tested at 293–1173 K

Abstract

According to the stoichiometric ratios of Mo-10Si-7B, Mo-12Si-8.5B, Mo-14Si-9.8B, and Mo-25Si-8.5B, some new Mo-Si-B alloys doped with 0.3 wt % lanthanum (III) oxide (La2O3) were prepared via liquid-liquid (L-L) doping, mechanical alloying (MA), and hot-pressing (HP) sintering technology. The phase-composition and microstructure were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The worn surfaces of the plate specimens were studied by confocal laser scanning microscopy (CLSM). Then, the tribological properties of Mo-Si-B alloy doped with sliding plate specimens of 0.3 wt % La2O3 were investigated against the Si3N4 ball specimens. The friction coefficients of Mo-Si-B alloys decreased and the wear rates of the alloys increased with test load. The high-temperature friction and wear behavior of Mo-Si-B alloy are related to the surface-oxidation and contact-deformation of the alloy at a high temperature. The low friction coefficients and the reduced wear rates are thought to be due to the formation of low friction MoO3 films. MoO3 changed the contact state of the friction pairs and behaved as lubricating films.

Study on the Pre-Oxidation and Resulting Oxidation Mechanism and Kinetics of Mo-9Si-8B Alloy

“…The density increase of oscillatory sintering can be measured by the Archimedes suspension wire method. Compared with traditional hot-pressing sintering, this density was increased by 9.25 g/cm 3 , and its relative density reached 97.78%.…”

“…The specific strength of the Si-C ceramic matrix composites was low, and its intrinsic brittleness was too large. It was not suitable for load-bearing parts of complex shapes in high-temperature circumstances, and it was difficult to connect ceramic matrix composites with metal materials [ 3 ]. The specific strength and oxidation resistance of Nb-Si alloy above 1300 °C were obviously weaker than that of Mo-Si alloy [ 1 , 2 , 3 , 4 ].…”

“…It was not suitable for load-bearing parts of complex shapes in high-temperature circumstances, and it was difficult to connect ceramic matrix composites with metal materials [ 3 ]. The specific strength and oxidation resistance of Nb-Si alloy above 1300 °C were obviously weaker than that of Mo-Si alloy [ 1 , 2 , 3 , 4 ]. It had been difficult to meet the high-temperature resistance requirements of high-temperature parts [ 5 ].…”

“…Supatarawanich et al [8] had found that Mo-Si-B alloys had better oxidation resistance at 1300 • C with the Si/B ratio close to 1. (3) The third way was to improve the oxidation resistance of the alloy by refining the grain, but as the grain boundaries increase, Si was more likely to segregate to the grain boundary, causing the strength of the grain boundary to decrease [9]. (4) At last, the pre-oxidation method was also reckoned as one of the potential ways to solve this problem.…”

Tribological behaviours of Mo–Si–B–xTi alloys against Al2O3 ceramic and AISI 52100 steel

“…However, they show a much higher friction coefficient and wear rate below 600°C. Li et al [21] compared the friction and wear properties of Mo–Si–B-based alloys with different chemical compositions under an applied load of 1.96–10.78 N at room temperature. The results indicate that all the Mo–Si–B-based alloys show a high friction coefficient and poor wear resistance.…”