Comparative Study on the Hardness and Wear Resistance of the Remelted Gradient Layer on Ductile Iron Fabricated by Plasma Transferred Arc

Abstract

Repairing the worn surfaces of wear-resistant workpieces, such as rollers, is one of the main application fields of surface treatment, but the repairing time is often not considered. In fact, the repairing time is very important, since it affects the repair quality and service life of wear-resistant workpieces. In this paper, a remelted gradient coating was prepared on a ductile iron plate by plasma transferred arc to simulate the repair treatment of wear-resistant workpieces. First, two positions in the remelted gradient coating were defined, i.e., the top of the gradient remelted layer was defined as M1, and the position where the hardness was two-thirds of the top of the remelting layer was defined as M2. Next, the time taken to repair the workpiece when the working surface reached M2 was proposed. Finally this method was verified by a comparative study on the microhardness and wear resistance of the M1 and M2. In this paper, the M2 was located at a ~0.5 mm from the top of the remelted gradient layer. The results show that the microhardness of the position of the M1 was higher than that of the position of the M2. However, the wear resistance of the M1 was worse, as confirmed by the wear rates. At the same time, cracks and fragments were observed on the worn surface of the M1 and M2 positions. Furthermore, the coefficient of friction (COF) of the position of M1 was noted to be first higher and subsequently lower than that of the position of M2, owing to the grinding ball entering the substrate. The abrasion mechanisms of both regions were observed to be complex, including oxidative wear, adhesive wear, delamination wear, and/or fretting wear. The experimental data indicate that it is feasible to determine the repair time according to the microhardness of workpieces.

Keywords

• microhardness
• wear resistance
• remelting
• ductile iron
• plasma transferred arc