Influence of B, Si Slagging Elements on Microstructure of Light Beam Alloying Layer.

The surface of HT-200 grey cast iron was alloyed with B, Si slagging elements and Cr, Ni alloying powder (Cr : Ni=20 : 80) by light beam. The results show that the formation of alloying layer depends on the protecting effect of B, Si slagging elements on melting metal; on the other hand, the alloying degree and microstructure uniformity depend on the influence of B, Si slagging elements on alloying process. When the dosage of B, Si slagging elements is too little (<5 mg), the formation of alloying layer is poor. While the dosage of B,Si slagging elements is too much (>20mg), the uniformity of composition and microstructure decreases. The top of the alloying layer is composed of γ (Fe, Ni) and (Fe, Cr)₃ C and α, while the bottom consists of blocky (Cr, Fe)₇C₃ on hypoeutectic structure matrix composed of γ (Fe, Ni) and ledeburite. When the dosage of B, Si slagging elements is between the two points, the good formation and micmstructure uniformity of alloying layer can be acquired. The alloying zone is hypoeutectic structure composed of γ (Fe, Ni) and ledeburite. [ABSTRACT FROM AUTHOR]