Surface modification of Al2O3–ZrO2(Y2O3) eutectic oxides by laser melting: processing and wear resistance

Abstract

Surface coatings of pseudo-binary Al2O3–Zr2O3(Y2O3) eutectic oxides were produced by laser melting of the surface of conventionally sintered materials using a high-power diode laser. It was possible to obtain smooth, homogeneous, and crack-free coatings up to 50_7 mm2 in area by carefully controlling the processing conditions (laser power, traveling speed of the specimen, and substrate temperature). The surface treatment was aimed at creating a dense, wear-resistant coating based on the eutectic microstructure generated upon solidification. The microstructure of the coating was formed by elongated colonies, and was similar to that found in rods grown by the laser-heated floating zone method at the same growth rates. The laser-melted coating presented much higher hardness and wear resistance than the sintered materials, and the optimum mechanical properties were measured in samples treated at 500 mm/h with a laser line power of 65–80 W/cm. These samples presented a hardness and wear rate of 19.770.4 GPa and 3.8_10_6 mm3/N m, respectively, while those of the conventionally sintered materials were 14.37 0.2 GPa and 2.3_10_6 mm3/N m.