Study on Cr-rare Earth-boronizing of the Steel 45 at Low Temperature

The Cr-Rare earth-boronized layers were fabricated on the steel 45 at 650°C for 6 h. The microstructure, phase composition, microhardness and tribological properties were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness tester and wear tester. The results showed the Cr-Rare earth-boronized layer was composed of single Fe2B phase. A sawtooth morphology was obtained in the Cr-Rare earth-boronized layer and the microstructure of the Cr-Rare earth-boronized layer was compact and dense. The thickness of the boride layer is about 23 μm. The boride tooth was thin and straight. The microhardness of the Cr-Rare earth-boronized layer was 1200HV∼1700HV, and first increased with the increase of distance from surface and then decreased when the distance from surface is longer than 7.5 μm. The hardness gradient of the boride layer is lessened. The wear resistance of steel 45 is greatly improved by Cr-Rare earth-boronizing.