Evaluation of microstructure characteristic of stellite6-B4C composite layer cladded by GTAW welding process on carbon steel

Microstructural characteristics of stellite6-B4C composite clad layer fabricated by GTAW were investigated on steel substrate. Mixtures of stellite6 with different B4C weight percentages were pasted on substrates. X-ray diffractometery (XRD) was used for structural evaluation of clad layers. Microstructural investigations of clad layers were conducted by optical microscopy (OM) and scanning electron microscopy (SEM) equipped with energy dispersive spectrometery (EDS). Hardness profiles of clad layers were obtained by microhardness testing method. According to the results the microstructure of composite clad layers contained a hypoeutectic structure. X-ray diffraction analysis showed the existence of cobalt-rich matrix together with eutectic carbides such as Cr7C3 and Cr23C6. It was suggested from the investigations that during the cladding process, boron carbides which were added to clad layer, melted completely and solidified again. B4C was found to have a preventing effect against the growth of dendrites tending to refinement of microstructure. The hardness increased with increasing B4C content up to 30 wt.%, but increasing B4C amount (40 and 50 wt.%) resulted in degradation of the hardness of composite clad layers.