Thermodynamic Calculations of Melt in Melt Pool During Laser Cladding High Silicon Coatings Original Research Article

Based on the Miedemaʹs formation heat model for binary alloys and the Toopʹs asymmetric model for ternary alloys, the formation heat, excess entropy, and activity coefficients of silicon ranging from 1 900 K to 4 100 K in the Fe-Si-C melt formed during the laser cladding high silicon coatings process were calculated. The results indicated that all values of ln γOSi, ɛCSI, ρSiSi and ρCSi are negative in the temperature range and these values increase as the temperature increases. And all values of ɛSiSi and ρSi-CSi are positive and these values decrease with increasing temperature. The iso-activity lines of silicon are distributed axisymmetrically to the incident laser beam in the melt pool vertical to the laser scanning direction. And the iso-activity lines of silicon in the front of the melt pool along the laser scanning direction are more intensive than those in the back of the melt pool. The activity of silicon on the bottom of the melt pool is lower than that in the effecting center of laser beam on the top surface of the melt pool and it may be the important reason for the formation of the silicides and excellent metallurgical bonding between the laser cladding coating and the substrate.