Fabrication and Characterization of Ni60A Alloy Coating on Copper Pipe by Plasma Cladding with Induction Heating

Abstract

Plasma cladding coupled induction heating was developed and successfully used to fabricate Ni60A coating on the surface of copper pipe. By matching the swing arc with the rotating copper pipe, the cladding efficiency was as high as 32.72 mm2/s. From the head to the tail of the coating, the wear resistance changed from 4.5 to 1.8 times that of pure copper. During the cladding process with constant current, the surface temperature of the cladding zone and the bath depth gradually increased. The corresponding dilution ratio increased, accompanied by the widening of the interface transition zone and the growth of precipitated phases (CrB and Cr23C6). Due to the gradient change of composition, the coating can be regarded as an in situ synthesized gradient coating. The critical point of sudden change of temperature in cladding zone was 850 °C, at which point the wear mechanism changed from abrasive wear to adhesive wear. The proper surface temperature of cladding zone should be controlled within 600–850 °C, which can be achieved by matching the cladding current and induction heating power. Results indicated that plasma cladding coupled induction heating is a potentially effective method to prepare high-quality coating on the surface of a large-complex-curved copper component.

Interface improvement of plasma cladded Ni-based coating on copper induced by substrate preheating

“…Q 3 is mainly related to the thermal conductivity ( λ ) and volume ( V ) of the copper substrate, which can be expressed as f ( λ , V ). Therefore, the temperature of molten pool ( T ) can be qualitatively expressed as [17]: For a copper substrate with a fixed volume, the heat dissipation capacity should be consistent. The P , I and v become the decisive factors to affect the temperature of molten pool ( T ).…”

“…The principle of plasma cladding process is shown in Figure 2. The details of the equipment and control system have been described in the previous study [17]. To investigate the influence of the preheating temperature on the interfacial connection of coating, the copper substrate was preheated to 300°C, 400°C, 500°C, 600°C, 700°C and 800°C by an induction heater (30 kW, Shanghai Renjun High Frequency Equipment Co., Ltd., China), respectively.…”

“…Q 3 is mainly related to the thermal conductivity (λ) and volume (V) of the copper substrate, which can be expressed as f (λ, V). Therefore, the temperature of molten pool (T) can be qualitatively expressed as [17]:…”

“…To overcome this difficulty, a new process of plasma cladding coupled with induction preheating was proposed in our group's previous research [17]. Results showed that the prepared Ni-based coating had a good metallurgical bond with the copper substrate.…”

“…In this cladding process, the preheating temperature of the copper substrate is the most critical process parameter. However, previous research [17] did not discuss the selection mechanism of preheating temperature in depth. To further explain the principle of preparing metallurgical bonded coating on copper by plasma cladding, the effect mechanism of preheating temperature on the interfacial connection of coating was investigated and discussed in this paper, which is a supplement to the previous research [17].…”