Laser surface alloying of AISI 1050 mild steel for cavitation erosion resistance using NiCrSiB

Abstract

Specimens of AISI 1050 mild steel were surfaced alloyed with NiCrSiB using a two-step process. NiCrSiB powder was flamed sprayed onto the substrate and the as-sprayed layer was remelted by a 2 kW continuous wave Nd:YAG laser to achieve surface alloying. The cavitation erosion resistance of the surface alloyed specimens in 3.5% NaCl solution at 23°C was determined by means of a 20kHz ultrasonic vibrator at a peak-to-peak amplitude of 30 m. The corrosion characteristics were studied using potentiodynamic polarisation technique. At a dilution ratio of 12% (corresponding to a laser scanning speed of 25 mm/s), the cavitation erosion resistance of the alloyed surface was 8.9 times that of the as-received AISI 1050 specimen, while at a higher dilution ratio of 48% (corresponding to a scanning speed of 15 mm/s), the erosion resistance dropped to 7.7 times. The corrosion resistance was also improved as reflected by a noble shift of the corrosion potential of about 150 mV, and a reduction in the current density of least one order of magnitude as compared with the as-received specimen at the same potential. The improvement in cavitation erosion resistance could be attributed to the formation of carbides and carbo-borides which increased the hardness, and the improvement in corrosion resistance was due to the increase in the Cr content in the alloyed layer.Specimens of AISI 1050 mild steel were surfaced alloyed with NiCrSiB using a two-step process. NiCrSiB powder was flamed sprayed onto the substrate and the as-sprayed layer was remelted by a 2 kW continuous wave Nd:YAG laser to achieve surface alloying. The cavitation erosion resistance of the surface alloyed specimens in 3.5% NaCl solution at 23°C was determined by means of a 20kHz ultrasonic vibrator at a peak-to-peak amplitude of 30 m. The corrosion characteristics were studied using potentiodynamic polarisation technique. At a dilution ratio of 12% (corresponding to a laser scanning speed of 25 mm/s), the cavitation erosion resistance of the alloyed surface was 8.9 times that of the as-received AISI 1050 specimen, while at a higher dilution ratio of 48% (corresponding to a scanning speed of 15 mm/s), the erosion resistance dropped to 7.7 times. The corrosion resistance was also improved as reflected by a noble shift of the corrosion potential of about 150 mV, and a reduction in the current density of ...