| Plasma cladding technology is a surface modification technology developed in recent decades. It has many advantages such as high production efficiency, high energy conversion efficiency, low equipment and maintenance cost, convenient operation and so on. So it has wide development prospects. Metal silicide MoSi2is usually used as wear resistant materials and high temperature oxidation resistant materials due to its characteristic of high melting point, high elastic modulus, proper density, high hardness, low thermal expansion coefficient, high ductile-brittle transition temperature, good thermal shock resistance and high temperature oxidation resistance. TiC cermet is always used as reinforced phase of wear-resistant composites because it has the characteristic of high hardness, high melting point, low density, good wear resistance, good thermal conductivity and conductivity.In this paper, wear and high temperature oxidation resistant composite coatin gs with MoSi2and TiC as reinforcing phase, solid solution of Fe or Ni as matri x phase were in situ fabricated on Q235low carbon steel substrate by plasma cl adding technology with Ni-36.3Mo-21.1Si-4.5C-18.1Ti (wt.%), Ni-27.2Mo-15.8Si-3.4C-13.6Ti (wt.%) and Ni-18.2Mo-10.5Si-2.2C-9.1Ti (wt.%) mixed alloy powder a s raw material respectively.The microstructure and phases composition of the coatings were identified by optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results show that the coating with Ni-36.3Mo-21.1Si-4.5C-18.1Ti (wt.%) mixed alloy powder as raw material is mainly composed of MoSi2, TiC, FeSi2and Ni2Si. The coating with Ni-27.2Mo-15.8Si-3.4C-13.6Ti (wt.%) mixed alloy powder as raw material primarily consists of MoSi2, TiC and y-(Fe, Ni). The coating with Ni-18.2Mo-10.5Si-2.2C-9.1Ti (wt.%) mixed alloy powder as raw material is predominantly composed of MoSi2, TiC andγ-(Ni, Fe). Microstructure of the coatings is fine and dense. Large irregular blocky primary phase MoSi2and small granular primary phase TiC are evenly distributed in the Fe-based or Ni-based solid solution matrix. The coatings are metallurgically bonded to the Q235low carbon steel substrate.Microhardness profiles along the depth direction of the coatings were measured by a Vickers hardness tester. Results show that the coatings have high and uniform hardness distribution. With the decrease of Ni content in the coatings, the microhardness values increase.Wear and friction properties of the plasma clad composite coatings were evaluated on pin-on-disc dry-sliding wear tester at room temperature. The results indicate that the coatings have low friction coefficient and low wear mass loss under dry-sliding wear test condition. And the wear mass loss of the coatings is insensitive to the applied loads, which implies that the coatings have excellent anti-wear performance under heavy loading tribological service conditions. Among the three Plasma clad composite coatings, the coating with Ni-27.2Mo-15.8Si-3.4C-13.6Ti (wt.%) mixed alloy powder as raw material has the best wear resistance.High temperature oxidation resistance of the coatings was detected by the BFX-12B type box electronic furnace. The results show that the plasma clad composite coatings have low oxidation mass gain during isothermal oxidation process under800℃,1000℃and1150℃condition. The oxidation kinetics curves are close to parabolical law, which implies that the coatings have excellent high temperature oxidation resistant. Among the three plasma clad composite coatings, the coating with Ni-27.2Mo-15.8Si-3.4C-13.6Ti (wt.%) mixed alloy powder as raw material has the best high temperature oxidation resistant. |
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