Search

In order to reveal the correspondence between the microstructure and mechanical properties of in-situ TiC/Ti composite coatings by induction fusion coating, the nano-mechanical property variation patterns of different phase structures within the coatings were investigated by using the isolated nanoindentation test method, and the mechanical properties of the coating micro-zone structure were studied by using grid indentation test method. The isolated indentation results show that the nanoindentation hardness and elastic modulus of the in-situ TiC-reinforced phases are 21.3 GPa and 275 GPa, respectively, while the average nano hardness of the matrix phase in the α-Ti-rich and β-Ti-rich regions is 4 GPa and 6 GPa, respectively, and the average elastic modulus is 130 GPa and 155 GPa, respectively. The correspondence between the grid indentation and isolated indentation test results is good. The minimum peak obtained from the three-peak Gaussian fitting of the fractional nanoindentation test results represents the mechanical properties of the matrix phase of the coating, the middle peak reflects the comprehensive mechanical properties of the coating, and the maximum peak is lower than the real mechanical properties of the in-situ TiC reinforcement due to the influence of the reinforcement size and indentation position. Under the consideration of coating microstructure and reinforcement size, by reasonably setting the fractional indentation test conditions and selecting the appropriate test area, it can reveal comprehensive properties of the coating while obtaining real mechanical properties of different phase structures of in-situ TiC composite coatings.

Induction cladding TiB/Ti composite coating was in-situ synthesized by induction heating the preplaced powder mixture of 90% Ti (atom fraction, the same below) and 10% boron on a Ti6Al4V substrate. The microstructure, phase composition and micro/nano mechanical properties of the coating were studied by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), microhardness tester and nanoindentation tester. The results indicate that the composite coating has a smooth surface and a dense microstructure without cracks and pores. A strong metallurgical adherence is formed between the coating and the substrate. During induction cladding process, B and Ti are fully reacted to in-situ form TiB reinforcements. The matrix of the coating consists of α-Ti phase and a few β-Ti phases. The reinforcements of in-situ synthesized TiB are uniformly distributed in the coating with a volume fraction about of 9.4%. Indentation hardness and modulus of the in-situ TiB particles are about 35 GPa and 545 GPa, respectively, which cause the increase of the microhardness of the composite coating to about 525HV0.2. It is increased by 67% as against the Ti6Al4V substrate.

Fe-Cr-Ni alloys are widely applied to aero-engine, industrial gas turbine and other equipment because of their high temperature strength and toughness and creep resistance. Four kinds of porous MgO reinforced Fe-Cr-Ni matrix composites, which are nano-MgO (34.9%)/Fe-Cr-Ni (mass fraction, the same below), micro-MgO (34.9%)/Fe-Cr-Ni, micro-MgO (25.7%)/Fe-Cr-Ni, micro-MgO (17.0%)/Fe-Cr-Ni, were prepared by powder sintering and in situ synthesis method. Effect of the particle sizes and content of MgO on bending strength at room or high temperature and oxidation resistance of porous metal matrix composites at high temperature were investigated by XRD, DTA and SEM. The results show that different raw materials lead to the different enthalpy, resulting in the different porosities and phase compositions for the sintered samples. The porous composites consist of Cr0.7Fe0.36Ni2.9, Cr-Fe and MgO phases generally. The bending strength of these porous composites decreases with the increase of the temperature. The high temperature oxidation resistance of nano-MgO (34.9%)/Fe-Cr-Ni composites is the best of the four kinds of porous composites.

In order to improve the high temperature tribological properties of Ti6Al4V alloy, multi-phase hybrid metal matrix high-temperature self-lubricating anti-wear composite coating was in-situ synthesized by laser clad with the powder precursor of Ni60-16.8%TiC-23.2%WS2(mass fraction, the same below). The microstructure, phase composition and tribological properties as well as the corresponding wear mechanisms of the composite coating at 20, 300, 600, 800℃ were analyzed systematically. The results show that the microhardness of the composite coating (701.88HV0.5) is about two-fold of the substrate (350HV0.5). Due to the synergetic effect of the in-situ synthesized solid lubricants Ti2SC/TiS/NiS/TiO/TiO2/NiCr2O4/Cr2O3 and hard phases (W,Ti)C1-x/TiC/Cr7C3, both the wear resistant and friction reducing capabilities of the composite coating are better than that of the substrate. With the increase of temperature, the friction coefficient and wear rates of the composite coating and the substrate all exhibit decreasing trend, i.e., the friction coefficient of the composite coating and substrate are 0.32, 0.43 and wear rates are 1.80×10-4, 2.92×10-5mm/Nm at 800℃, respectively. The main wear mechanisms of substrate are mainly plastic deformation and delamination as well as oxidation wear, while the composite coating is predominated by the oxidation wear and slight adhesive wear at 800℃.

Chitosan, extenders anointed and in-situ synthesis method were used to synthesize anode-composite lead-carbon batteries.SEM, EDS, BET and RM were used to characterize and analyze the morphology of carbon materials.The results show that chitosan-carbon has non-crystal structures.Its pore size distribution is between 5-10nm.Specific surface area reaches to 487.4m2/g.The negative composite material electrode is mixed with a conductive agent to produce pastel.Pb-C analog battery was assembled.Electrochemical workstation is used to test chronoamperometry curves, electrochemical impedance spectroscopy so as to evaluate the possibility of in-situ synthesis anode composite material and its potential value of practical application.Electrochemical testing results show that the Pb-C negative plate,which is made by anode composite carbon material as the carbon source of in-situ synthesis of chitosan, possessing better electrochemical performance and smaller resistance.Its specific capacitance of cyclic voltammogram test is 162.9F/g with longer first discharge platform,the ultimate capacity reaches to 108.722mAh·g-1 when chitosan as carbon source, the specific capicity is 98% of the theoretical capacity. After 1000times of cycle there is almost no decay in capacity.

The self-shielded flux cored wire was used to test the surface of Q235 steel, and the Fe-Cr-C-B-Ti alloy was prepared by adjusting the content of Ti in the flux cored wire.The change rule of mechanical properties of surfacing alloy was obtained through hardness and wear test. The phase composition and microstructure of the alloy were investigated by X ray diffraction (XRD) and scanning electron microscopy (SEM).The results indicate that with the increase of Ti content, TiC and TiB2 hard phase particles are formed in the surfacing layer, and TiC is preceded by TiB2 production.A large number of dispersed TiC and TiB2 can play an important role in the wear process and wear resistance of the deposited metal. The hardness of the surfacing layer is increased from 56.5HRC to 66HRC, and the wear loss weight is decreased from 0.5772g to 0.0487g when the mass fraction of Ti in the surfacing alloy is increased from 0.15% to 1.43%.

Aluminum matrix composites reinforced by in-situ Al3Ti particles were successfully synthesized from an Al-Ti system via a direct melt reaction. The influences of Ti additions, ultrasonic time and power on the microstructure and mechanical property of composites were systematically investigated. The results show that the Al3Ti particles are refined obviously and the distribution also becomes more uniform with the increase of ultrasonic power. Meanwhile, the addition of Ti refines the α-Al dendrite phases in the matrix, which gradually changes from the original coarse to fine branch crystals, rose-like or nearly spherical. However, results also show that the size of Al3Ti particles decreases to a minimum value and then increases with the increase of ultrasonic time. The trends of the mechanical properties are consistent with the microstructures of the Al3Ti/ADC12 composites. The optimum parameters of the composite are 3%Ti (mass fraction) content, 1.5kW ultrasonic power, 20kHz ultrasonic frequency and 6min ultrasonic time. Accordingly, the tensile strength and elongation of the composite synthesized reach to 247.34MPa and 2.31% respectively, increasing by 21.3% and 50.0% compared with the unmodified alloy.