Influence of Mo on the microstructure and mechanical properties of TiC-based cermets

The microstructures and mechanics properties of TiC-based cermets composed of TiC, WC, Ni, Co, Mo, and Cr3C2 were investigated. The results show that Mo has a great effect on the sintering densification, microstructures, and mechanical properties. The microstructures and distribution of Mo and Ti in the TiC-based cermets were analyzed. It was indicated that a new phase with Ti, Mo, W, and C was formed on the rim of （Ti,W）C grains by means of an addition of Mo into the TiC-based cermets. The new phase with a surrounding structure was of great aid to improve the wettability of the liquid phase on the solid phase surface of TiC, decrease the porosity and refine the grains of the hard phase, which gave rise to the increase in strength and hardness. The properties of the TiC-based cermets could be further improved to some extent by adding WC, Cr2C3, and Co.

Effect of Rare Earths on Microstructure and Properties of TiC-based Cermet/Cu Alloy Composite Wear Resistant Materials

The effect of rare earth (RE) oxide on the microstructure and properties of TiC based cermet/Cu alloy composite hardfacing materials was investigated by using scanning electron microscope (SEM), transmission electron microscope (TEM), impact test and wear test. The mechanism of RE oxide for improving the phase structure and the impact toughness was also discussed. The experimental results indicate that the microstructure of the matrix can be refined, and the micro-porous defects can be eliminated by adding RE oxide into the composite materials. The polycrystalline and amorphous phase structure is formed at the interface of cermet and matrix metal. The formed structure enhances the conjoint strength of interface. The frictional wear resistance can be improved obviously, although the microhardness of the matrix metal can not be effectively increased by adding RE oxide.

Effect of V content on microstructures and properties of TiC cermet fusion welding interface

The effects of vanadium(V)on the microstructures and mechanical properties of the TiC cermet fusion welding interface were studied by adjusting the content of V in the self-developed flux-cored wires using metal inert gas arc(MIG)welding for surfacing on the TiC cermet.The results show that the increase in V content promotes the element diffusion between TiC cermet and weld metal.There are no de-fects observed in the interface,and the diffusion of elements refers to excellent metallurgical bonding.The shear strength of the fusion zone initially decreases and then increases with the increase in V content.The maximum shear strength of the TiC cermet/weld interface,reaching 552 MPa,occurred when the V content reached 0.65%.Meanwhile,the average hardness in the transition zone reached 488.2 HV0.2.

Effect of VC/Cr_3C_2 on microstructure and mechanical properties of Ti(C,N)-based cermets

Effects of VC/Cr3C2 on the microstructure and mechanical properties of Ti（C,N）-based cermets were studied. The microstructure was investigated by means of optical microscopy, X-ray diffractometry as well as scanning electron microscopy in combination with energy dispersive spectrometry. Mechanical properties, such as transverse rupture strength, hardness and fracture toughness, were measured. The results show that there are black core-grey rim structure and white core-grey rim structure in the microstructure. The grains become fine due to the VC/Cr3C2, and the grains of cermet added with 0.75VC/0.25Cr3C2 are refined most remarkably. The black core becomes finer with the increase of VC addition and rim phase becomes thicker with the decrease of Cr3C2 addition. The porosity increases with the increase of VC addition in VC/Cr3C2. Compared with the cermet free of VC/Cr3C2, the transverse rupture strength and hardness of cermets with VC/Cr3C2 are both improved, and the maximum values are both found for the cermet with 0.25VC/0.75Cr3C2. The fracture toughness can be effectively promoted by adding VC/Cr3C2 with an appropriate ratio of VC to Cr3C2, and the maximum value is found for the cermet with 0.5VC/0.5Cr3C2.

Stainless steel binder for the development of novel TiC-reinforced steel cermets

Steel reinforced TiC composites are an attractive choice for wear resistance and corrosion resistance applications. TiC- reinforced 17-4PH maraging stainless matrix composites were processed by conventional powder metallurgy （P/M）. TiC-reinforced maraging stainless steel composites with 〉97% of theoretical density were fabricated. The microstructure, mechanical and wear properties of the composites were evaluated. The microstructure of these composites consisted of spherical and semi-spherical TiC particles. A few microcracks appeared in the composites, showing the presence of tensile stress in the composites produced during sintering. Typical properties, namely, hardness and bend strength were reported for the sintered composites. After heat treatment and aging, the increase of hardness was observed. The increase of hardness was attributed to the aging reaction in the 17-4PH stainless steel. The precipitates appeared in the microstructure and were responsible for the increase in hardness. The specific wear behavior of the composites was strongly dependent on the content of TiC particles, the interparticle spacing, and the presence of hard precipitates in the binder phase.

EFFECT OF Mo AND Mo_2C ON THE MICROSTRUCTURE AND PROPERTIES OF THE CERMETS BASED ON Ti(C,N)

Effect of Mo and Mo2 C on the microstructure and properties of Ti（C,N）-based cermets was investigated in this article. The results have indicated that the weight percentage of Mo from 5 to 10 can reduce Ti（C,N） grain diameter and thickness of the rim, and Ti（C,N） grain can be wetted by Ni-Cu-Mo liquid so as to get small contiguity of Ti（C,N） grain. In that way, the transverse rupture strength of Ti（C,N）-based cermets has reached 1800-1900 MPa; the fracture toughness has been due to 16-18 MPa.m1/2. But 15 wt pct Mo was not more effective on Ti（C,N）-based cermets, because the thickness of the rim becomes larger. In the circumstance of Mo2 C, 5 wt pct Mo2 C was good for microstructure and properties of Ti（C,N）-based cermets, but 11 wt pct Mo2C has resulted in larger contiguity of Ti（C,N） grain and big Ti（C,N） grain diameter so as to reduce transverse rupture strength and fracture toughness. So that, the effect of Mo on Ti（C,N）-based cermets is better than Mo2C.

Effects of molybdenum on the microstructure and mechanical properties of Ti(C,N)-based cermets with low Ni

The effects of Mo on the microstructure and mechanical properties of Ti（C,N）-based cermets with low Ni have been studied systematically. Different contents of Mo （4-12 wt.%） were added into Tl（C,N）-based cermets. Specimens were fabricated by conventional powder metallurgy and vacuum sintered at temperatures of 1440, 1450, and 1460℃ individually. The microstructure and fracture morphology were investigated by scanning electron microscope, and the mechanical properties such as transverse strength and hardness were measured. The results show that the microstructure is uniform and the thickness of rim phase is moderate when the content of Mo is 8 wt.%; the mechanical properties of the specimens sintered at 1450℃ are better than those sintered at 1440 and 1460℃. The integrated properties of transverse strength and hardness are the best when the content of Mo is 8 wt.% and the sintering temperature is 1450℃.

Phase Evolution during the Sintering of Submicron Ti(C,N)-Based Cermets

The submicron powder mixtures of TiC-TiN-WC-Mo-C-Ni sintered at 1400degreesC or below in vacuum were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses. The results showed that Mo2C formed at 800degreesC or below. Both WC and Mo2C disappeared at 1200degreesC, and TiN disappeared at 1250degreesC. In addition, the variations of lattice constants of the titanium carbonitride and nickel binder phase with sintering temperature were experimentally obtained, and the reason was analyzed.

Tribological properties of TiAlN-coated cermets

Ti（C,N）-based cermets were coated with TiAlN using multi-arc ion plating technology. Sliding wear tests were performed on the coated cermets. The microstructure and morphologies of the coated cermets before and after friction and wear tests were characterized. The results show that the TiAlN coating surface was smooth and its root mean square roughness was 16.6 nm. The hardness （HK） of TiAlN coating layers reached approximately 3200 and the critical load （Lc） under which the coating failure occurred was 59 N. The sliding wear test results show that the friction coefficients of the TiAlN-coated cermets were lower than that of the cermets without any coating. Under the same load, the adhesion phenomenon of the counterpart materials on the specimens was improved and the mean friction coefficient increased with increasing sliding velocity. When the sliding velocity was 0.26 m·s^-1, the mass of the coated cermets reduced. At the same sliding velocity, the average friction coefficient of the TiAlN-coated cerrnets was lower under a higher load. The wear mechanisms of the TiAlN-coated cermets were mainly adhesive and abrasive wear.

Effect of VC addition on the microstructure and properties of Ti(C,N)-based nano cermets

In this paper, Ti（C,N）-based nano cermets were prepared by nano particles, and the effect of VC addition on the micmstructure and properties of Ti（C,N）-based nano cermets was investigated. The results showed that there existed black-core grayish-rim strucmre as well as gray-core grayish-rim structure in VC-doped Ti（C,N）-based nano cermets. With the increase of VC addition, the number of gray cores in- creased, the lattice parameter of Ti（C,N） phase increased, the grain size decreased, the hardness and fracture toughness of Ti（C,N）-based nano cermets were enhanced, and nearly full densification could be achieved. However, excessive addition of VC to 1 wt% resulted in slight decrease in hardness and fracture toughness. Some deep dimples were found in the fracture surface of cermets with VC addition, which corresponded to ductile fracture.

Preparation of ultrafine WC-Co cermets by combining pretreatment and consolidation with spark plasma sintering

Ultrafine-grained WC-Co bulk materials were prepared by a new method that contains pretreatment of the milled powder mixture and subsequent spark plasma sintering （SPS）. Ball milling parameters and the pretreatment temperature have significant effects on the microstructure and properties of WC-Co cermets. The prepared cermets have a mean grain size of less than 0.5 μm even with a pretreatment temperature as high as 1300℃. The WC-10wt.%Co cermet bulk prepared by the optimized milling, pretreatment, and SPS processing achieves excellent mechanical properties with a Vickers hardness of HV 1643, a fracture toughness of 13.1 MPa.m^1/2 and a transverse rapture strength of 3100 MPa.

Microstructure and cutting performance of Ti(C, N)-based cermets heat-treated in nitrogen

Ti（C, N）-based cermets were treated using hot isostatic pressing （HIP） at 1423 K in nitrogen. The microstructures compared with the as-sintered cermets were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray analysis, and electron microprobe analysis. It was found that high nitrogen activity in the surface zone resulted in the formation of gradient structure. Approximately 20-1am-deep, nitrogen-rich and titanium-rich hard surface zone was introduced by the heat treatment. The nitrogen activity was the driving force that caused the transportation of the atoms through the binder, titanium towards the surface, and tungsten and molybdenum inwards. In the surface zone, the particle size became fine, the inner rim disappeared, and the volume fraction of the outer rim and the binder phase considerably reduced. Small grains of TiN, WC, Mo2C, and nitrogen-rich carbonitlide phases formed in the surface zone during the heat treatment, improving the tlibological property of the heat-treated cermet.

Microstructure and mechanical properties of hot isostatically pressed cermets with TiN coatings

To increase the adhesion strength between the coating and the substrate, sintered Ti（C,N）-based cermets were selected and deposited with monolayer TiN using a multiarc ion-plating technique; subsequently, hot isostatic pressing （HIPhag） treatment was performed at 1000℃ using nitrogen pressure up to 110 MPa. The mechanical properties of cermets after a coating process and subsequent HIPing treatment have been evaluated with respect to the hardness, the residual stress, and the coating adhesion. The results show that atter the HIPing process, there was a higher increase ha critical load ha the TiN-coated cermets with lower surface roughness compared with those with higher surface roughness. In all cases, the residual stress was found to be compressive. The effects of substrate surface roughness and posttreatment on the adhesion strength of the coatings were thus investigated. It was also fotmd that the HIPing posttreatment process is well suited for hacreasing the adhesion strength between the coating and the substrate.

Dissolution-precipitation mechanism of self-propagating high-temperature synthesis of TiC-Cu cermets

The mechanism of self-propagating high-temperature synthesis （SHS） of TiC-Cu cermets was studied using a combustion front quenching method. Microstructural evolution in the quenched sample was observed using scanning electron microscope （SEM） with energy dispersive X-ray （EDX） spectrometry, and the combustion temperature was measured. The results showed that the combustion reaction started with local formation of Ti-Cu melt and could be described with the dissolution-precipitation mechanism, namely, Ti, Cu, and C particles dissolved into the Ti-Cu solution and TiC particles precipitated in the saturated Ti-Cu-C liquid solution. The local formation of Ti-Cu melt resulted from the solid diffusion between Ti and Cu particles.

Microstructure and mechanical properties of WC-Co,WC-Co-Cr_3C_2 and WC-Co-TaC cermets fabricated by spark plasma sintering

Spark plasma sintering was successfully used to produce WC-Co cermets with the addition of Cr3C2and TaC grain growth inhibitors. The spark plasma sintered compacts were investigated by scanning electron microscopy, X-ray diffraction analysis, density measurements, hardness tests, fracture toughness tests and elastic modulus tests. The results were comparedwithan inhibitor-free WC-Co cermet consolidated under the same process parameters. By using Cr3C2and TaC additives, it is possible to improve the hardness and fracture toughness of WC-Co cermets, but Cr3C2has better grain growth inhibition propertythan that of TaC. The best combination of hardness （HV30（2105±38）） and fracture toughness （（8.3±0.2）MPa·m^1/2） was obtained by the WC-5Co-2Cr3C2 cermet.

Comparative study of the fabrication of ultrafine Ti(C,N)-based cermets by spark plasma sintering and conventional vacuum sintering

Spark plasma sintering (SPS) and conventional vacuum sintering (VS) wereemployed to fabricate ultrafine Ti(C,N)-based cermets. The shrinkage behavior, microstracture, andporosity and mechanical properties of the samples fabricated by SPS were compared with those of thesamples sintered by VS using optical microscopy, scanning electron microscopy, universal testingmachine, and rockwell tester. The results are as follows: (1) The shrinkage process occurred mainlyin the range of 1000-1300 deg C during the VS process, and only a 0.2 percent linear shrinkage ratioappeared below 800 deg C; during the SPS process, a 60 percent dimensional change occurred below800 deg C as a result of pressure action. (2) By utilizing the SPS technique, it is difficult forobtaining fully dense Ti(C,N)-based cermets. Due to the much existence of pores and un-combinedcarbon, the mechanical properties of the sintered samples by SPS are inferior to sintered ones byVS. (3) grain size of the samples sintered by SPS is still below 0.5 urn, but not by VS; because oflow sintering temperature, there are no typical core/rim structures formed in the sintered samplesby SPS1; the main microstructures of the sintered samples by SPS2 are a white core/grey shellstructure, whereas by VS show a typical black core/grey shell structure.

Effect of sintering atmosphere on microstructure and properties of TiC based cermets

The effect of the sintering atmospheres (vacuum, N_2, Ar) on the microstructures and properties of the TiC based cermets was studied using XRD, SEM/BSE and energy dispersive spectrometer. Compared with the alloy sintered in vacuum, the carbon content of the specimen sintered in N_2 and Ar is lower by 0.5%; and the nitrogen content is higher by 0.3% when sintered in nitrogen. The central part of the ring structure may be carbide with either a high W or Ti content. The ring structures are (Ti, W, Ta, Mo, Co, Ni)C solid solutions with different metallic elements and distributions. The composition of the binder phase is (Co, Ni) solid solution with different Ti, W, Ta, Mo, C contents. The structures are uniform for the cermets sintered in vacuum and the properties are the best. When sintered in Ar or N2, the O_2 and N2 in the atmosphere take part in the sintering reaction to break the carbon balance in the cermets to form a shell structure and defects, which results in poor density, microhardness (HV) and transverse rupture strength (TRS).

MECHANICAL PROPERTIES AND MICROSTRUCTURES OF Ti(C,N) BASED CERMETS

ＭＥＣＨＡＮＩＣＡＬＰＲＯＰＥＲＴＩＥＳＡＮＤＭＩＣＲＯＳＴＲＵＣＴＵＲＥＳＯＦＴｉ（Ｃ，Ｎ）ＢＡＳＥＤＣＥＲＭＥＴＳ￥ＬｉｕＮｉｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｅｒｉｎｇ，ＡｎｈｕｉＩｎｓｔｉｌｕｔｅ...

Microstructures and properties of PVD TiAlN coating deposited on cermets with different Ti(C,N)grain size

In the present work,TiAlN coatings were deposited on Ti(C,N)-based cermet substrates by physical vapor deposition method.Emphasis was focused on the influence of grain size of cermet substrates on the microstructure,growth behavior,mechanical properties,adhesion strength and wear behavior of the coatings.The results show that finer Ti(C,N)grain size leads to higher nucleation density and lower growth rate of coatings,indicating the crystallite size of the TiAlN coatings decreases with decreasing Ti(C,N)grain size.Nanoindentation tests show that the coatings deposited on cermets of the finest grain size exhibit the highest hardness(H),elastic modulus(E),H/E and H3/E2 of 34.5 GPa,433.2 GPa,0.080 and 0.22,respectively.The adhesion strength between coating and substrate is also enhanced with decreasing Ti(C,N)grain size by scratch test,which corresponds to the grain size and H/E and H3/E2 of the coating.Besides,the lower surface roughness and better mechanical properties of the coating deposited on finer grained cermet contribute to the better wear resistance of the coating.

EFFECT OF RARE EARTH ELEMENT Er ON STRENGTHENING OF INTERFACE OF Ti（C，N） BASED CERMETS

ＥＦＦＥＣＴＯＦＲＡＲＥＥＡＲＴＨＥＬＥＭＥＮＴＥｒＯＮＳＴＲＥＮＧＴＨＥＮＩＮＧＯＦＩＮＴＥＲＦＡＣＥＯＦＴｉ（Ｃ，Ｎ）ＢＡＳＥＤＣＥＲＭＥＴＳ￥ＬｉｕＮｉｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｅｒｉｎｇ，...