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Ni-Cr coating and Ni-Cr/ZrO2 gradated coating were deposited on C45 carbon steel by high velocity arc spraying and micro-plasma spraying to solve the high temperature oxidation problem of medium carbon steel components. The oxidations of Ni-Cr coating, Ni-Cr/ZrO2 gradated coating and C45 carbon steel substrate were carried out for up to 108 hours in air atmosphere at 1100°C. The oxidation behaviors were investigated after detailed examinations by thermal gravimetric analysis (TGA), x-ray diffraction (XRD) and scanning electron microscopy (SEM). Ni-Cr coating and Ni-Cr/ZrO2 gradated coating show similar and low dynamics curve near to the logarithms function. Surface observations with SEM and XRD reveal that the oxidizing surface of the C45 carbon steel substrate is mainly a loose spherical structure consisted of mainly Fe2O3 and Fe3O4. The surface structures of Ni-Cr coating and Ni-Cr/ZrO2 gradated coating after 108 hours oxidization are rather denser than that of C45 carbon steel, which can effectively improve the properties of the oxidation resistance of C45 carbon steel substrate.

Both the complex permittivity and permeability of nanometer SiC and nanometer SiC/CNTs composite were investigated by Hewlett-Packard 8510B Network Analyzer. The results show that the complex permittivity of nanometer SiC/CNTs composite is much higher than that of nanometer SiC. Reflection curves of nanometer SiC and nanometer SiC/CNTs composite calculated with electromagnetic wave transmission-line theory show that the addition of CNTs at 6 wt%, 12 wt% and 18 wt% in nanometer SiC absorber can improve its microwave absorption properties strongly. There is a relationship between the mass fraction of CNTs and microwave absorption ability. With increase of the mass fraction of CNTs, its microwave absorption ability firstly increased then decreased. From the simulation, it was found that nanometer SiC with 12 wt% CNTs gave the optimum microwave absorption. The corresponding frequency of maximum reflection loss value of nanometer SiC/CNTs composite gradually moves to the low frequency range with increase of thickness. The maximum reflection loss value of nanometer SiC/CNTs composite (CNTs content is 12 wt%) was -25.74dB at the corresponding frequency of 11.60 GHz with a bandwidth under -5 dB (68% absorption) is 7.16 GHz when the thickness is 2.0 mm.

Samples of AISI 1045 carbon steel were surface hardened by micro plasma transferred arc (PTA) process. The hardened layer was characterized using both light optical and scanning electron microscopy and microhardness techniques. The tribological properties of the surface hardened layer and untreated substrate were investigated using a block-on-ring tribometer sliding against GCr15 steel under unlubricated condition. The worn surface morphologies and dominant wear mechanisms were identified using microscopy techniques. Results show that the surface hardened layer consists mainly of martensite and retained austensite with fine and dense structure, the microhardness of hardened layer increases from approximately HV 200 to HV 600. The wear volume loss of plasma hardened layer was 81.86×10-11m3 much better than that of untreated AISI 1045 carbon steel (743.44×10-11m3). Wear of untreated AISI 1045 carbon steel occurred by combined mechanisms of adhesion, abrasion and plastic deformation. While the worn surface of surface hardened layer is quite better with slight track and thin oxides on the worn surfaces. Plasma surface hardening has essentially changed the wear mechanism of the AISI 1045 carbon steel to slight abrasion and oxidation wear.

Nonastructured Al2O3-13wt%TiO2 (AT13) coatings were deposited by multi-function micro-plasma spray and Metco 9M plasma spray, respectively. Constituent phases and the microstructure of the powder particles and coatings prepared were examined with the aid of scanning electronic microscope (SEM) and X-ray diffraction (XRD). Mechanical properties including hardness and bonding strength were also evaluated by microhardness tester and electron tensile tester. Multi-function micro plasma sprayed nanostructured AT13 Coating is fully-melted, dense and uniform. However, AT13 Coating deposited by Metco 9M plasma spray is partial-melted. The microhardness of multi-functional micro plasma sprayed AT13 Coating is HV975.7~1441.7, much higher than that of Metco 9M plasma sprayed AT13 Coating (HV655.3~946.6). The bonding strength results present the same, increased from 19.8 MPa to 42.7 MPa.

Al2O3 coatings were fabricated by multi-functional micro-plasma spray through axial powder feed. The flight particle velocity and temperature were measured by SprayWatch-2i. With the rising of Ar flow, the velocity of Al2O3 particles increases, but the temperature of particles decreases gradually. Al2O3 coatings were analyzed by SEM and XRD. The microstructure of coatings is density, low porosity and uniform morphology. X-ray diffraction results show that α-Al2O3 is the main phase in the original Al2O3 powders, but Al2O3 coatings consist of γ-Al2O3 and a small amount of α-Al2O3. The microhardness and bonding strength of Al2O3 coatings were also measured, which is HV0.11183~1387 and 28.6MPa, respectively.