TiC Ni Cermet Research Articles

Effects of secondary carbide addition on the mechanical properties of (Ti1-xTMx)C-based 20Ni cermets (TM = V, Mo, and W): a study combining ab initio calculation and experimental results

ABSTRACT In recent years, significant efforts have been devoted towards the development of high-performance cermets with superior hardness and fracture toughness for engineering applications. In this study, a (Ti1-xTMx)C solid solution of a Ni cermet was prepared based on a combination of ab initio calculation and experimental results. The structural stability, mechanical properties, and microstructure of the cermet were investigated. A screening process was conducted using ab initio calculations to determine the optimal composition of (Ti1-xTMx)C (TM = V, Mo, and W) (x = 0–0.3125). The enhancement of the mechanical properties was analysed by calculating the electronic properties of the (Ti1-xTMx)C solid solutions. Additionally, we evaluated the powder morphology, microstructure, and mechanical properties of (Ti1-xTMx)C–20Ni by using experimental methods. The (Ti0.7W0.3)C–20Ni cermet exhibited enhanced hardness and fracture toughness in relation to conventional TiC–Ni cermets. Computational and experimental results indicated that the addition of secondary carbides improved the overall material properties.

Interfacial microstructure and mechanical properties of the TiC-Ni cermet/Ag-Cu-Zn/Invar joint

TiC-Ni cermet and Invar was brazed with Ag-Cu-Zn alloy in vacuum and the interfacial microstructure and mechanical properties were studied. The interfacial microstructure of the joint brazed at 910 °C for 10 min was TiC-Ni cermet/(Ag) + (Cu, Ni) + TiC/(Cu, Ni) + (Ag)/(Cu, Ni)/(Cu, Ni) + (Fe, Ni)/Invar alloy. When the temperature increased from 740 °C to 940 °C, (Cu, Ni) reactive layer at the cermet side dissolved into the brazing seam and became discontinuous. Moreover, TiC particles presented gradient distribution in the reactive region of the joint brazed between 850 °C and 940 °C. Meanwhile, the amount of (Cu, Ni) detaching from the cermet and entering the brazing seam increased. The shear strength firstly increased and then sharply decreased with temperature. The maximum shear strength of 161 MPa was obtained at 910 °C for 10 min and the joint was fractured on (Ag). The change trend of the shear strength between 820 °C and 940 °C was attributed to the increase thickness of the functional gradient material layer in the reactive region and the decrease of the (Cu, Ni) amount in the penetration region and the reactive region with the temperature increase.

Microstructure evolution and wettability of Ag[sbnd]Cu[sbnd]Zn alloy on TiC[sbnd]Ni cermet

Wetting of AgCuZn alloy on TiCNi cermet was performed using a sessile drop method in vacuum and the interfacial microstructure was studied. A continuous (Cu, Ni) solid-solution layer was formed at the AgCuZn/TiCNi cermet interface held at 810 °C for 10 min. According to the TEM results, an orientation relationship between the (Cu, Ni) solid-solution layer and the TiC particle at the interface was determined: TiC[42¯ 0]//(Cu, Ni) [0 2¯ 2], TiC(00 2¯ )//(Cu, Ni)(111). As the temperature increased to 960 °C, the (Cu, Ni) solid-solution layer dissolved into the liquid alloy and changed from continuous to discontinuous. The continuing growth of the (Cu, Ni) solid-solution layer at the interface at 810 °C was controlled by the Ni diffusion process from the TiCNi cermet to the liquid alloy. The average contact angles of the AgCuZn alloy and AgCu alloy on the TiCNi cermet were 19° and 121.5° at 810 °C, respectively. And the temperature increase had little effect on the final contact angle.

TiC/Ti3AlC2–Co plasma-sprayed coatings with excellent high-temperature tribological properties

In this work, TiC/Ti3AlC2–Co cermet coatings with varying amounts of Ti3AlC2 were deposited by atmospheric plasma spraying (APS) process and their wear-resistant properties were discussed. The friction coefficients and wear rates at high-temperatures were measured through a ball-on-disk type friction test at 600 °C. In addition, the corresponding wear mechanisms were elucidated through the observation of phase changes and surface microstructural evolution of the coatings. The results indicated that the as-prepared coatings consisted of TiC, Ti, TiO2, Al2O3, Co and CoO phases, which were produced by the decomposition and oxidation of TiC and Ti3AlC2. Compared with other samples, the sample with 30 wt% Ti3AlC2 addition displayed the smallest friction coefficient and least wear rate. Its wear rate was about 1.26 times lower than that of reported TiC–Co cermet material and about 10 times lower than that of the typically used TiC–Ni cermet material, suggesting outstanding wear resistance at elevated temperature. The addition of Ti3AlC2 reduced the friction coefficient of the coating by producing more TiC and Al2O3 hard phases and a consequent reduction of coating porosity. When the amount of Ti3AlC2 in the coating was less than 30 wt%, the main wear mechanism was abrasive wear. As the content of Ti3AlC2 was increased in the coating, the wear mechanism changed from abrasive wear to adhesive wear and the wear pattern of the coating gradually transformed from the furrows to the debris. This transformation of mechanism was related to the synergistic effect of hardness and porosity of the coating, which resulted from the remaining content and the special layered structure of Ti3AlC2.

Tribological properties of B4C–TiB2–TiC–Ni cermet coating produced by HVOF

Abstract In this study, B4C–TiB2–TiC–Ni coating was sprayed on the surface of 4130 steel by high velocity oxy-fuel torch. The tribological behavior of samples was studied by ball on disk wear testing. Structural evolution of the coating was analyzed by X-ray diffractometry. The microstructure of the coating, wear track and Al2O3 ball was investigated by scanning electron microscopy, field emission scanning electron microscopy and optical microscopy. Elemental analysis of the wear track was done by energy dispersive X-ray spectroscopy. It was found that a cermet coating containing B4C, TiB2, TiC and Ni phases with good bonding to the 4130 steel substrate with no sign of any cracking or pores was formed. The wear mechanism of the composite coating was delamination. The friction coefficient of samples was decreased with increasing load because of higher frictional heat and creation of more oxide islands.

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

TiC0.7 cermets with 20 vol% NiTi binder, containing up to 1.8 vol% Mo, were prepared by pressureless liquid-phase sintering at 1380 °C for 60 min. The pore size, apparent porosity, TiC grain size and binder mean free path length decreased with increasing Mo content up to 1.2 vol%. Further increasing the Mo content to 1.8 vol% resulted in a MoTi phase formation. Upon Mo addition, the carbides obtained a core-rim structure with dissolved Mo in the rim. The Mo distribution in the carbide and binder phases of the TiC0.7-NiTi and TiC-Ni cermets was correlated with the calculated Ti-Mo-C and Ti-Mo-Ni phase diagrams. The hardness significantly increased with increasing Mo addition up to 1.2 vol% and saturated upon further increasing the Mo content, while the bending strength remained almost the same. The E-modulus increased with increasing Mo addition up to 1.8 vol%, whereas the fracture toughness decreased.

Reactive wetting of TiC-Ni cermet by Ag-Cu-Zn alloy during evaporation

In order to investigate the effect of the evaporation on wetting, reactive wetting of TiC-Ni cermet by molten Ag-Cu-Zn alloys with different Zn contents was studied at 810 °C using a sessile drop method in vacuum. The vapor recoil force induced by the strong evaporation of Zn in the Ag-Cu-25Zn alloy drove the spreading of the molten Ag-Cu-25Zn alloy. Furthermore, the sequential evaporation of Zn in the Ag-Cu-25Zn alloy caused the formation of a (Cu, Ni) solid-solution layer at the interface between the TiC-Ni cermet and the Ag-Cu-Zn alloy. Thus, the (Cu, Ni) solid-solution layer could serve as a metallization layer on the surface of the TiC-Ni cermet, which promoted the non-wetting to wetting transition of the TiC-Ni cermet by the Ag-Cu-25Zn alloy. The equilibrium contact angle of the Ag-Cu-25Zn alloy on the TiC-Ni cermet was 19.9°, approximately equal to that of a Ag-28Cu eutectic alloy on a Cu-Ni alloy surface. The final contact angle of the Ag-Cu-Zn liquid alloy on the TiC-Ni cermet first decreased and then increased as the Zn content in the liquid was increased from 0% to 30%. It reached a minimum value in the Ag-Cu-25Zn alloy.

Tribological performances of ZrC-Ni and TiC-Ni cermet reinforced PTA hardfacings at elevated temperatures

The aim of this study was to characterise TiC-Ni and ZrC-Ni cermet reinforced NiCrBSi hardfacings in a 40:60vol.% ratio respectively and to investigate their respective wear behaviour at temperatures up to 700°C. Coatings were produced using plasma transferred arc welding; optimised methods and parameters were meant to ensure a uniform distribution of the cermet across the metal matrix composite. High-temperature testing included macro hot-hardness, cyclic impact abrasion, and cyclic abrasion, all featuring temperatures between room temperature and 700°C. During cyclic abrasion, both TiC-Ni and ZrC-Ni reinforced hardfacing show decreasing wear rate with increasing temperatures. During impact abrasion testing, it was shown that TiC-Ni and ZrC-Ni reinforced hardfacings possess superior wear properties in comparison to conventional WC reinforced ones. The role of TiO2 oxide, and in the case of ZrC-Ni, the role of a complex mixed carbide phase, M23C6, played an important role in stabilising the kinetics of oxidative wear at temperatures beyond 500°C.

(Ti,W)C–Ni cermet prepared by high-energy ball milling and subsequent carbothermal reduction of TiO2–Ti–WO3–C mixture

A single-phase (Ti,W)C solid solution was prepared by high-energy ball milling of TiO2–Ti–WO3–C powder mixtures with various TiO2/Ti ratios and subsequent carbothermal reduction. Thermodynamic calculations suggest that the reaction pathways would follow the sequences WO3→WC, TiO2→Ti2O3, Ti(CO)→TiC, Ti2O3→TiC, and TiC+WC→(Ti,W)C. The reaction pathways were substantiated by measuring CO gas evolution and heat flow using QMS and DSC, respectively. The 80(Ti,W)C–20Ni powders were sintered in vacuum at 1510°C and their mechanical properties were evaluated. The toughness values of (Ti,W)C–Ni cermet were significantly higher than those of TiC–Ni cermet owing to the alloying effect of W in TiC. The composition of raw powder mixture also affected the mechanical properties of (Ti,W)C–Ni after sintering. The toughness was improved when TiO2/Ti ratio was 2 in the raw powder mixture than when pure Ti or TiO2 was used. The enhanced toughness is attributed to larger (Ti,W)C grain size.

Milling performance of TiC–Ni cermet tools toughened by TiN nanoparticles

A novel indexable TiC-based cermet tool (named tool A) with intra/intergranular microstructure has been designed and fabricated in application of face milling of a medium carbon steel (AISI 1045) in the dry condition comparison with commercial WC-Co tool (named tool B). Compared to the tool B, the newly as-prepared cermet tool A had an advantage of high speed cutting performances in cutting carton steel. Wear behavior was investigated in order to better understand the relationship between outstanding cutting properties and microstructure. The improved cutting performance of tool A can be attributed to the rim reinforced by TiN nanoparticles.

Microstructure of TiC/Nb-Ni Cermets Cladding Layer

This paper reports an investigation of the effect of Nb additions on the microstructure of TiC–Ni cermets, which is prepared by plasma cladding technique. The composition of the cermets cladding layer was observed by scanning electron microscope (SEM) in combination with energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) analysis was carried out for phase identification. The microstructure has a trend to become finer with the increase of Nb additions, however, when the Nb addition goes to 15 wt%, the ceramic particles become much bigger and cause large amounts of cracks. Then the component variation of different parts of the ceramic particle was analyzed using the EDS, and explained the reason of the variation and why the rim structure wasn't formed.

Effect of Ni contents on the microstructure and mechanical properties of TiC–Ni cermets obtained by direct laser fabrication

Abstract TiC–Ni cermets have been produced using direct laser fabrication on a low carbon steel substrate, with 20, 30 and 40 vol.% Ni, respectively. The effects of Ni content on the microstructure and mechanical properties of TiC–Ni cermets were investigated. The TiC particles were produced by an in-situ reaction of titanium and graphite during the direct laser fabrication, instead of being directly injected into the laser molten pool. The results showed that in the cermets only TiC and Ni were present as phases, indicating that TiC was synthesised by the in-situ reaction of Ti and C in the powder mixture and the amount of Ni content did not influence the presence of phases in the final products. Moreover, the results revealed that the increase of Ni content will result in the decrease of bending strength and micro-hardness.

An in situ (W,Ti)C–Ni composite fabricated by SHS method

The combustion synthesis reaction was combined with liquid phase sintering to fabricate net-shape TiC–Ni and TiC–WC–Ni composites in a single processing operation. When Ti and C powders used for in situ production of TiC–Ni cermet, the final product was porous and had low strength. By the addition of fine W powder with W/Ti=1 molar ratio, the product contained (Ti,W)C, W2C and mix compounds of type Ni2W4C. Using W with W/Ti=2 molar ratio results in a dense high strength product containing (Ti,W)C and WC.

Microstructures and mechanical properties of nanoTiN modified TiC-based cermets for the milling tools

Abstract Cermets are wear-resistant materials used in cutting tool applications, but in some applications (e.g. the heavy interrupted cutting), their brittleness is still a limitation for extending the range of their utilizations. Recent experiments have shown that nano-modified cermets with nanometer TiN particles distributed at the grain boundaries can acquire high toughening. The materials are composed of hard-phase grains surrounded by a tough binder-phase. The mechanical properties are influenced by ceramic and metal phases. In the present work, first of all, the effect of the binder phases on the microstructures and mechanical properties of the nanoTiN modified TiC-based cermets for the milling tools are investigated in order to further improve their comprehensive properties. Results show that transverse rupture strength (TRS) and fracture toughness are increasing with rising amount of the binder phases, however, the hardness decreases correspondingly. At the same time, the materials based on TiC–Ni–Co have shown some improvement of fracture toughness and transverse rupture strength compared to TiC–Ni cermets. Moreover, the appropriate Mo addition can refine the microstructures of the nanoTiN modified TiC-based cermets, but reduce the toughness of the materials. In the end, fracture analysis photographs indicate that the main failure mode of the tested samples is transgranular and intergranular fracture.

Dissolution–precipitation mechanism of self-propagating high-temperature synthesis of TiCNi cermet

Abstract A mechanism of self-propagating high-temperature synthesis (SHS) of TiCNi cermet was studied by means of a combustion front quenching method. Microstructural evolution in the quenched sample was observed using a scanning electron microscope (SEM) with energy dispersive X-ray (EDX) spectrometry, and the combustion temperature and velocity were measured. The results showed that the combustion reaction started with a local formation of a TiNi liquid solution and could be described with a dissolution–precipitation mechanism, namely, Ti, Ni, and C particles dissolved into the TiNi solution and TiC particles precipitated in the saturated TiNiC liquid solution. The local formation of the TiNi solution resulted from a solid diffusion between the Ti and Ni particles, and it was found that the dissolving rate of Ti particles is higher than the Ni particles. In addition, the combustion synthesis has incompleteness and it was attributed to a usage of the coarser Ni and Ti powders. Again, a model corresponding to the dissolution–precipitation mechanism was drawn, and an ignition temperature of the combustion reaction was prophesied as about 942 °C.

Preparation of ultrafine TiC–Ni cermet powders by mechanical alloying

Pure titanium, nickel and carbon powders were mechanically alloyed to synthesize the TiC–Ni cermet powders with ultrafine microstructures. As a result of milling, formation of the ultrafine TiC or amorphous Ti–Ni phase were obtained, depending on milling conditions. The effect of milling variables on the synthesizing behaviour of the powders was investigated. The sintered TiC–Ni cermet from the mechanically alloyed powders contained TiC particles of 0.2–1.5 μm in size as compared with those of 3–5 μm for a commercial cermet. The spex-milling technique of the mechanical alloying process turned out to be more effective in the formation of the final cermet microstructure than the ball-milling one.

Effect of coalescence on the grain coarsening during liquid-phase sintering of TaC–TiC–Ni cermets

During heat treatment of TaC–2TiC–30Ni (in wt%) specimens at 1400°C, abnormally large and faceted (Ta, Ti)C grains appeared. These abnormal grains usually coalesced with surrounding small grains and grain boundaries were formed between them. Inside the abnormally grown large grains, many small grains were entrapped. The observed abnormal grain growth (AGG) was explained in terms of a two-dimensional nucleation controlled growth mechanism. Coalescence was suggested to enhance the growth rate because re-entrant edges due to grain boundaries provide easier two-dimensional nucleation sites.

Sintering properties of submicron TiC powders from carbon coated titania precursor

The sintering behavior of submicron titanium carbide (TiC) synthesized from carbon coated titania (TiO2) precursor was investigated in TiC-Ni system. The densification was examined as functions of initial carbon content (30.95–34 wt.%) and Ni content (3–20 wt.%). The sintered density of TiC-Ni was markedly decreased with increased carbon content in the precursor. The amount of Ni had a relatively small influence on the densification of submicron TiC-Ni cermet compared with TiC (commercially available HCS)-Ni cermets. The results show that submicron TiC with only 3 wt.% Ni can be sintered to densities above 95% TD in flowing Ar+10H2 at 1500°C and below. The improvements in densification result from the capillary force increase since it is inversely dependent on the particle size. With decreased Ni content, the Vickers hardness increased and the fracture toughness decreased, as expected. However, the sufficient densification cannot be achieved for commercial HCS TiC powder sintered with Ni (<10 wt.%) under the same conditions. Therefore, both the Vickers hardness and fracture toughness decreased as the Ni content decreased. This was due to the increase of porosity in the sintered samples containing commercial TiC powder.

Determination of three-dimensional grain size distribution by linear intercept measurement

For grains of any shape, a computer simulation technique to calculate the probability of finding a certain intercept length is suggested and the results are given for cubic, tetragonal and hexagonal grains. The distribution of linear intercepts measured is then converted into that of a three-dimensional (3D) size. The developed method is applied to determine the 3D distribution of cubo–spherical grains observed in the TiC–Ni cermet.

Martensitic transformation in cermets with metastable austenitic binder: II. TiCFeNiC

New cermets consisting of TiC(Fe23Ni1.5C) (mass%), whose binder phase exhibits an f.c.c.-to-b.c.t. martensitic transformation have been made and their mechanical properties and crystallography have been investigated to determine the influence of transformation on the fracture toughness of the cermet. As a result, the toughness of the cermet is found to be higher than that of a conventional TiCNi cermet, whose binder phase does not undergo martensitic transformation, although the hardness is not much different comparing the two. It is also found that characteristics of the thermally induced martensite in the binder phase, such as the M s temperature, are quite different from those of bulk specimens of the same composition as the binder phase. The results described above are similar to those for a WC(Fe23Ni1.5C) cermet previously investigated.