Parameterization and Process Influence of Graphite Morphology in the Laser Cladding of Grey Cast Iron
X-H. Zhan, Y-C. Liu, P. Yi, T. Liu, R. Sun and C-F. Fan
The existence of graphite affects the clad quality of cast iron; therefore, the thorough study of the graphite phase during the laser cladding of grey cast iron has important significance. Based on the analysis of the thermo–mechanical coupling characteristics and behavior rule of the graphite phase, the morphological parameters of graphite were extracted and depicted in this paper. Subsequently, the relationship between the process and graphite morphological parameters in the laser cladding procedure was analysed by double lap cladding experiment. Results indicated that four parameters were established to characterize the morphology of graphite: area percentage, A; average aspect ratio, R̄, and tip characteristics, α(≤90°) and β(>90°). The A and the R̄ decreased with the increase of the specific energy, while the β(>90°) increased. The β(>90°) in the binding zone is greatly improved compared with that in the heat affected zone (HAZ), the A of graphite in the binding zone is much lower than that in the HAZ. Limited by the diffusion distance, the alloy elements only had effects on the residual graphite morphology in the bonding zone. The A of graphite increased with the increase of Si element, while the β(>90°) decreased. Meanwhile, the augmented contents of Ti and Cr elements promoted the formation of carbide; consequently, the A decreased while the β(>90°) increased. The R̄ of graphite in the binding region are ignored.
Keywords: CO2 laser, grey cast iron, Fe314 alloy, silica, Si, chromium, Cr, titanium, Ti, iron, Fe, powder, laser cladding, process parameters, thermo–mechanical coupling, microstructure, graphite morphology, heat affected zone (HAZ)