Papers by Keyword: TiC

Abstract: TiC base high manganese steel-bonded carbide was manufactured by powder metallurgy technique, and the effect of adding mode of WC additive on microstructural evolution and properties of the alloy was studied. SEM microstructure showed that surrounding structure appeared obviousely with WC additive; while microstructure of the alloy was well-distributed and particle shape was distinct very much. The shape of TiC particles became irregular with pure WC powder addition, and irregular with further increase of WC content, and the shape of some TiC particles became angular because of excessive reaction between TiC particles and WC additive. microstructure of the alloy was refiner and the strength, toughness were improved with the increase of WC addition. (Ti, W)C solid solution is superior to form on the surface of TiC particles through dissolution precipitation mechanism because the activity energy of WC was higher than that of TiC-WC compound carbides when WC was added in the alloy, and the particle shape of TiC became more irregular and the properties were improved significantly.

Abstract: TiC base high manganese steel-bonded carbide was manufactured with conventional powder metallurgy method to service in wear and impact resistant condition. WC was added in the alloy in the form of (W,Ti)C carbides to improve the impact toughness and expand the applications of alloy, meanwhile, cobalt powder was also used to enhance the wettability of the metallic binder on the ceramic phase. Results showed that the impact toughness of the alloy was increased remarkably with the increase of WC content. The impact toughness reached 10.6 J/cm² when WC content was 10.5 wt.%, while the hardness of the alloy did not decrease. It was indicated that the appropriate content of WC and cobalt can improve impact toughness and wear resistance of the alloy greatly with little increase in the production cost.

Abstract: Pre-alloyed Fe/Mo powder was manufactured by water atomization method with different molybdenum contents of 1.6%, 2.21%, 2.87%, 4.34%, 6.5% (in wt. %),respectively, and this powder was used as binder to fabricate TiC steel-bonded carbide. The mean grain size of the ball milled powders was smaller because of the increase of hardness and brittleness due to the existence of molybdenum in Fe/Mo pre-alloyed powder TiC phase grew slowly and uniformly owning to the uniform distribution and low activity of molybdenum as a result of the adding method (compared with the adding method of pure metallic molybdenum powder), whereas the abnormal grain growth was suppressed. Results showed that the microstructure of the alloy was finer obviously and the density, hardness, strength and impact toughness of the alloy all increased to some extent.

Abstract: Ball milling is an efficient way to produce TiC steel bonded carbide. In addition to the use of alloy steel ball, a certain amount of cylindrical object are used for grinding medium and the content is 0, 15%, 30%, 50%, 100% of the total grinding body, respectively. The results show that average size of particles became smaller with an increase of the content of cylindrical grinding medium. The effect of ball milling is the best when the content of cylindrical grinding medium was 30%. Meanwhile the effect on ball milling with cylindrical grinding medium entirely is not better than that with spherical grinding ball completely. In addition, the ball milled powder is made into experimental samples after mixing glue, granulation, forming, sintering and heat treatment and son on. The particle size of ball milled powder become smaller and the green compact are sintered in lower temperature and kept shorter holding time after adding cylindrical grinding medium in ball mill, which reduces the tendency of growing up of hard phase and improve mechanical properties of the sintered material distinctively.

Abstract: Considering the multi-porous and rimous Fe-Cr series alloy coatings deposited on Q235 steel by plasma arc welding, the mass fraction of 0%, 2%, 4%, 6%, 8% Ti is mixed into Fe-Cr alloy powder. The microstructure and characteristics of the Fe-Cr series alloys with a range content of Ti were investigated using optical micrograph (OM), X-ray diffraction (XRD), scanning electron micrograph (SEM) Digital Micro-hardness Tester and M-2000 dry abrasion tester. The major phase of the Fe-Cr layers is dendrite with the lath carbide mixed between the limb of dendrite and the grains refine with addition of Ti. The XRD result indicates the main phases are (Fe-Cr) solution, Cr₂₃C₆, and TiC, while the result of Digital Micro-hardness test shows the microhardness increases with the mass fraction of Ti till it comes to 4% and decreases with the following addition of Ti. The highest average hardness of layer is 750HV with content of 4% Ti, while the coating with 2% Ti appears better wear resistance with the least wear volume for the match of toughness matrix and hard phase. Hence, the coating with 2% to 4% Ti shows the best property.

Abstract: In situ synthesized TiB_x/TiC reinforced composite coatings were prepared on Ti-6Al-4V substrate by laser in situ deposition using 10B₄C-18TiNi-72Ti-6Al-4V (wt. %) powder blends as the feedstock materials. The microstructural analysis of the composites was performed using scanning electron microscope, and phase analysis was done with X-ray diffraction. The results showed that the composite coatings contained long needle TiB, irregular block TiB₂ and disperse particles/dendrites TiC, the thick rod phase which was a inlay structure consisted of TiB₂ and TiC. These composite reinforced phases were evenly distribution in the (TiNi+Ti₂Ni+α–Ti) substrate.

Abstract: A double-layer composite coating on Q235 steel substrate was prepared using a new developed in situ technology consisting of SHS reaction, laser cladding and metal dusting techniques. A double-layer composite coating consists of the TiO₂–TiC ceramic outer layer and the TiC-CNTs cermet inner layer. An excellent bonding was observed among the outer layer, the inner layer and the steel substrate. Corrosion behavior of the coating was investigated and the commercial 304SS was used for comparison. The outer layer exhibited the highest corrosion resistance and 304SS the lowest corrosion resistance, whereas the inner coating exhibited the intermediate corrosion resistance. However, the severe pitting corrosion which was observed in 304SS did not exist for the coating.

Abstract: The aim of this paper is to study the effect of jatropha curcas biodiesel on the corrosion behavior of surface modified low alloy steel after modification by TIG torch surface melting technique. The coating layer was produced by preplacement of 1 mg/mm² TiC particulate into the surface of AISI 4340 steel and at heat input of 1344 J/mm using an electric arc generated from the tungsten electrode that melt the powder with substrate material to form a composite layer. The micrograph of the composite coated surface modified steel showed formation of TiC dendrites that densely populated at the of the melt pool which contributes to the high hardness value. The corrosion behavior of the composite coated steel was studied using tafel extrapolation method in biodiesel environment. The surface micrograph after corrosion test shows pitting corrosion holes as a dominant corrosion phenomenon for AISI 4340 steel. The tafel curve showed reduction of corrosion current density of the surface modified steel compared to the alloy street substrate.

Abstract: Tungsten inert gas (TIG) melting process is increasingly find successful application in many aspects of engineering part components. In this study, TIG melting of Fe-based coating has been successfully developed by precoated iron, carbon and silicon (Fe-C-Si) powders on commercial purity titanium (CP-titanium) surface under three different glazing speeds such as 1.0 mm/s, 1.5 mm/s and 2.0 mm/s and constant energy input of 1350 J/mm in an argon gas environment. The effects of glazing speeds on the surface topography, melt geometry, microstructure and hardness were investigated. Rippling marks were found on all the track surfaces which portends that good solidification of the molten melt pool had taken place near the base metal. The melt pool layers consisted of higher population of dendrites and the population were found to decrease with increasing glazing speeds. The resolidified surface layer of the dendrites developed hardness 3 to 4 times higher than that of the base material. According to the enthalpy reactions due to formation of titanium carbide, silicon carbide and iron carbide during TIG melting of Fe-C-Si coated titanium surface are considered to be responsible for larger melt depth. These results showed that surface properties of CP-titanium can be enhanced with Fe-C-Si using TIG melting process.

Abstract: In this work the stability of TiN and TiC nanopowders in isopropyl alcohol as well as the fabrication of dense and well adhered thin coatings based on TiN and TiC by electrophoretic deposition (EPD) have been evaluated in terms of zeta potential and mass deposited when hydrazine is added. The surface of TiN and TiC nanoparticles has been modified to improve the dispersion in isopropyl alcohol adding a cationic polymer (polyethylenimine) as dispersant with two different molecular weights. The influence of acidic/basic character of the solvent also has been evaluated in order to reach the most efficient EPD process. It was found that the adsorption of polyethylenimine with higher molecular weight can preserve the homogeneity of TiC coatings. The surface of TiN nanoparticles can be tuned in order to achieve a similar polyethylenimine adsorption which also improves the deposition in basic media.