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

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.

Influence of Process Parameters on Microstructure of Reaction Plasma Cladding TiC-Fe-Cr Coating

In order to improve the quality and properties of the coating, a certain amount of Ti was added to the plasma cladding Fe-Cr-C coating in the early stage. And Fe-Cr-C-Ti composite powder was prepared by precursor carbonization-composition process. In situ synthesized TiC-Fe-Cr coatings were fabricated on substrate of Q235 steel by plasma cladding process with Fe-Cr-C-Ti composite powder. Microstructure of the coating with different process parameters, including cladding current, cladding speed, number of overlapping cladding layers, were analyzed by scanning electron microscope (SEM). The results show that the structure of the TiC-Fe-Cr coating is greatly affected by the fusion current, the cladding speed and the overlapping cladding process. In this test, when the cladding current of 300A and the cladding process parameter of the cladding speed of 50 mm/min are clad with three layers, a well-formed and well-structured TiC-Fe-Cr coating can be obtained. Which are the best synthetic process parameters in this test.

Effect of Titanium Addition on Cracks of Fe-Cr-C Coating by Reactive Plasma Cladding

Fe-Cr-C and Fe-Cr-C-Ti coatings were prepared by reactive plasma cladding in this paper. The crack morphology and fracture surface of the Fe-Cr-C coating were observed by SEM. The effect of titanium addition on the crack of Fe-Cr-C coating was analyzed. The results show that the coating cracks mainly consist of crack perpendicular to the fusion line, defect-induced crack and intergranular crack. The crack rate of Fe-Cr-C-Ti coating was obviously decreased after Titanium was added. When the titanium content is below 8 wt.%, with the increase of titanium content, the crack rate of Fe-Cr-C-Ti coating decreases obviously. When titanium content is between 8wt.% and 13wt.%, there are no cracks in the Fe-Cr-C-Ti coating. When the titanium content exceeds 13 wt.%, with the increase of titanium content, a small number of cracks begin to appear. The addition of titanium increases the toughness of the Fe-Cr-C-Ti coating and reduces the stress concentration.