Microstructure and properties of TiB 2-containing coatings prepared by arc spraying

Abstract

Low cost arc spraying and cored wires were used to deposit composite coatings consisting of TiB 2 and TiB 2/Al 2O 3 hard particles in a Ni(Cr) and stainless steel 304L matrix. Four coatings were prepared namely Ni(Cr)–TiB 2, Ni(Cr)–TiB 2/Al 2O 3, 304L–TiB 2 and 304L–TiB 2/Al 2O 3. The microstructural characteristics of powders and coatings were observed by scanning electron microscopy (SEM). Phase compositions of powders were analyzed by X-ray diffraction (XRD). Although all the analyzed coatings exhibited similar lamella structure, remarkable differences not only in the morphology of hard phase and matrix but also in the size and distribution of hard phases were observed from one coating to another. Tribological behavior of the coatings was analyzed in room temperature dry sliding wear tests (block-on-ring configuration), under 75 N at low velocity (0.5 m/s). The coatings showed far high wear resistance than low carbon steel substrate under same conditions examined. Wear loss of 304L–TiB 2 and Ni(Cr)–TiB 2 coatings were lower nearly 15 times than that of steel substrate. TiB 2 hard phases in coatings bonded well with metal matrix contributed to high wear resistance.