Microstructure and properties of TiB2-containing coatings prepared by arc spraying

Low cost arc spraying and cored wires were used to deposit composite coatings consisting of TiB2 and TiB2/Al2O3 hard particles in a Ni(Cr) and stainless steel 304L matrix. Four coatings were prepared namely Ni(Cr)-TiB2, Ni(Cr)-TiB2/Al2O3, 304L-TiB2 and 304L-TiB2/Al2O3. 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-TiB2 and Ni(Cr)-TiB2 coatings were lower nearly 15 times than that of steel substrate. TiB2 hard phases in coatings bonded well with metal matrix contributed to high wear resistance.