Papers by Keyword: Nano-Al₂O₃p

Abstract: Three NiCoCrAlY cladded coatings reinforced by different contents of nano- Al2O3p and one without nano-Al2O3p were prepared on a Ni-base super alloy using laser cladding technique. Hot corrosion of the NiCoCrAlY coatings in Na2SO4/K2SO4 (75:25, wt. /wt.) mixture was performed at 1050 °C in static air. The effects and influencing mechanism of nano-Al2O3p on the hot corrosion behavior of the coatings were discussed. Results indicate that the hot corrosion resistance of the coatings with nano-Al2O3p is better than that of the one without nano-Al2O3p, among which the one with 1.0 wt. % nano-Al2O3p presented the best hot corrosion resistance. The improvement of the hot corrosion resistance is largely due to the refinement of the microstructure after adding nano-Al2O3p.

Abstract: To study effects of nano-Al2O3p (nanometric Al2O3 particles) on high temperature frictional wear behaviors of the NiCoCrAlY coating (a high temperature protective coating), three NiCoCrAlY coatings strengthened by different contents of nano-Al2O3p were prepared on a Ni-based super alloy by using laser cladding technology and their dry frictional wear behaviors at 500 °C in static air were investigated. The comparison was made with the coating without nano-particles. The results show that the frictional coefficient of the coatings increased with the hardness after adding nano-Al2O3p and the wear resistance of the coatings was enhanced. Among nano-Al2O3p-added coatings, the coating added with 1.0 wt% nano-Al2O3p performs best. The wear rate of the coating is only 58% of the coating without nano-particles. Moreover, the improvement of the oxidation behavior plays an important role in improving the high temperature wear resistance.

Abstract: NiCoCrAlY coatings strengthened by different content of nano-Al2O3p, using crosscurrent CO2 laser, were prepared on Ni-based superalloy substrates, and thermal shock behaviors of these coatings were investigated by cycling between 1050°C and room temperature (forced water quenching).The results show that the thermal shock resistances of nano-Al2O3p-added coatings are definitely better than that without adding nano-Al2O3p. Among the nano-Al2O3p-added coatings, the coating added with 0.5wt% nano-Al2O3p performs best. After 10 thermal shock cycles, the spalled and spalling area in the oxide scale of the no-nano-Al2O3p coating reaches up to 27.7%, and the main failure form of the oxide scale is an expanding unit-spalling type in thermal shock cycles. While the area in the oxide scale of nano-Al2O3p-added coatings is only 10%~60% to the no-nano-Al2O3p one, and the failure of these oxide scales is mainly in the form of unit-spalling type. After 100 thermal shock cycles, many cracks turn up in the cross-section of the no-nano-Al2O3p coating, including propagating crack and internal crack. While no internal crack appeared in nano-Al2O3p-added coatings, and the propagating cracks are smaller than no-nano-Al2O3p one.