| Wear-resistant materials has been developed at express speed in petroleum, chemical industry, nuclear power and mining industries, so the demand of the performance improvement is following. Ni-Cr-B-Si of nickel-based alloy has become the ideal wear-resistant alloy, because it has low melting point, good liquidity, good corrosion resistance, abrasion resistance, heat resistance and oxidation resistance and other comprehensive performance. Plasma surfacing (PTAW) technology has been widely used in the welding reinforcement of wear-resistant alloy because of its parent metal lower dilution rate, dense surfacing layer without defects and the advantages of good metallurgical bonding. In this paper, Surface hardening of304L stainless steel was achieved by the plasma-transferred arc welding (PTAW) deposited with nickel base alloy and compound nickel base alloy in which niobium powder was added. The influence of the welding current and niobium powder content on the microstructure, microhardness and wear resistance of different nickel base alloy welding layer were studied by metallographic microscope, scanning electron microscopy (sem), electron probe, XRD diffraction, fluorescence spectrum analyzer, microhardness and wear testing machine equipment.The results show that the NbC phases appear in both the coating of Nb/Ni40composite alloy powder and the coating of Nb/Ni60composite alloy powder by diffraction patterns and EDS analysis, and it is proved that NbC phase can be composed through reaction of the Nb element and C element during the plasma welding process. The NbC has a bad moldability, when the amount of added Nb is2.5wt%. while the NbC has a good moldability, when the amount of added Nb is5wt%. When the amount exceeds10wt%, the Nb element diffuses into eutectic leading to the form of multi eutectic compounds.The influence of welding current on the dilution rate of substrate and the thickness of the coating is significant during the plasma surfacing process of composite alloy. The lower current leads to the lower coating, while the higher current makes that the amount of Fe is too much, and it will affect the performance of the coating.After adding Nb powder with different levels into Ni40alloy powder, there is a significant change appearing in the organization of coating. with the amount increased, chromium compounds change from the basic shape to flakiness (2.5wt%), flower-shaped (5wt%), strip (10wt%) and mesh (15wt%), the particles of the dendrite are going to be refined, the volume fraction will increase, and the number of intergranular chromium compounds are also reduced. The Analysis and comparison prove that the best performance of the coating is obtained with adding5wt%Nb powder and under the140A current.After adding Nb powder with different levels into Ni60alloy powder, there is a significant change appearing in the organization of coating. With the increasing amount of the Nb powder, chromium compounds change from the basic shape to lath, block and flower-like (2.5wt%), lath-shaped, needle-like and flower (5wt%), wheat-like (10wt%) and feathering (15wt%). The Analysis and comparison prove that the best performance of the coating is obtained with adding5wt%Nb powder and under the140A current. |
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