Characteristics of surface remelted hardfacing spheroidal graphite cast iron using the plasma transferred arc process

Abstract

The plasma transferred arc (PTA) process was used to obtain a 2–5 mm thickness remelted hardfacing layer on the spheroidal graphite cast iron surface. Cementite structure can be observed on the surface layer, exhibiting a significantly high hardness due to rapid solidification. The composition of 3.54 wt pct carbon and 2.48 wt pet silicon remains fixed throughout the PTA surface remelting experiment. To study the effect of substrate microstructure on the remelted hardfacing layer, experimental parameters including spheroidal graphite nodule count and the microstructure of matrix are conducted.Experimental results confirm that the remelted hardfacing layer is accompanied by a large amount of Fe3C eutectic cementite. If the PTA remelting input current is increased, the volume fraction of eutectic cementite tends to decrease, subsequently decreasing the hardness. An increased spheroidal graphite nodule count of the substrate tends to decrease the hardness of the remelted hardfacing layer. The substrate with ferritic matrix shows increased hardness over a pearlite structure. Furthermore, while the impact angle is fixed at 30°, the erosion wear resistance increases with the increasing hardness of the remelted hardfacing layer, but this tendency is contrary when the impact angle is fixed at 90°.