Study On Microstructure And Mechanical Properties Of Spray Welding Layer Of WC Enhanced Ni-based Alloy And Fe-based Alloy

Ni-based alloy and Fe-based alloy with good wear-resistance, corrosion resistance and oxidation resistance are widely used in the field of equipment manufacturing industry to protect and repair the worn parts. The high velocity flame spraying and the plasma transferred arc welding are widely used in the industrial production due to its advantages including high utilization rate, low dilution rate and high spray efficiency, etc.In this paper, Ni-based alloy which include the content of Ni pack WC range from 0% to 30% were deposited on the surface of 45 steel by the high velocity flame spraying and Fe-based alloy which include the content of WC range from 0% to 13% were deposited on the surface of 45 steel by the plasma tranferred arc welding. The coatings of Ni-based alloy and Fe-based alloy were charaterized by optical microscope(OM), scanning electron microscope(SEM), X-ray diffractometer(XRD), electronic dispersive spectrometer(EDS) and microhardness tester. The friction and wear properties were investigated on the friction-wear testing machine. On this basis, the best wear resistance of Ni-based alloy coating and the Fe-based alloy coating did the grinding experiment to study the effect of different loads on the friction and wear properties. The results show that:(1) Ni-based alloy coating is composed of fused layers and surface layers. The sub-grain is form include plane crystal, dendrites and equiaxed. The microstructure of the Ni-based alloy coating consistes of γ-Ni matrix and the other precipitates, such as WC, FeNi3, Cr2Ni3. When the content of Ni pack WC varies in the range from 0% to 27%, the coating of unmelted WC particles increases with the increasing of the content of Ni pack WC. At the same time, the hardness and wear resistance increase with the increasing of the content of Ni pack WC. When the content of Ni pack WC is 27%, the surface hardness is the highest and the surface wear resistance is also the best. Wear resistance increases about 1 times than without Ni pack WC. When the content of Ni packs WC increase to 30%, the coating appears macroscopic crack. The modes of strengthening for Ni pack WC are mainly dispersion strengthened. The wear mechanism includes adhesive wear and abrasive wear, etc.;(2) Fe-based alloy coating is composed of fused layers, nearly fused layers and surface layers. The sub-grain forms include flat crystal, dendrites and equiaxed. The microstructure of the Fe-based alloy coating is mainly consiste of α-Fe matrix and CrFe4 phase. With the increasing of the content of WC, The second phase precipitates, such as Fe7C3, W2 B, Cr3C2, etc., increase. During the process of the plasma spray, the WC particles can decompose and it is no longer dispersion strengthened in the original forms. At last, the second phases precipitate in the form of W2 B, Cr3C2. When the content of WC varies in the range from 0% to 13%, the hardness and wear resistance first increase and then decrease with the increasing of the content of WC. When the content of WC is 10%, the surface hardness reaches to the highest value and wear resistance is the best. Wear resistance increases about 1 times than without WC. The wear mechanism is adhesive wear, abrasive wear and partial oxidation wear.(3) When the applied load is 10 kg and 20 kg, the wear resistance of the coating of the Fe-based alloy including 10% WC is better than that of the Ni-based alloy including 27% Ni pack WC. When the applied load is 30 kg and 40 kg, the wear resistance of the coating of Ni-based alloy including 27% Ni pack WC is better than that of Fe-based alloy including 10% WC.