Composition Of Binder Phase Research Articles

Microstructures and mechanical properties of the bilayer functionally graded WC-TiC-Ni/Co cemented carbides

The nitridation of the WC-TiC-Ni/Co cemented carbides successfully yielded a bilayer-graded structure that consists of face center cubic-rich outer and coarse grain intermediate layers. The sintered carbides were nitrided at 1723 K under 4 MPa N2 for 90 min. The bilayer gradient showed a unique microstructure combination of element distribution and grain features. The graded microstructures contributed to the hardness and fracture toughness of the outer layer, intermediate layer, and inner region. The fracture mode of the intermediate layer was mainly a transgranular fracture, which increased the fracture toughness of the intermediate layer. The fracture mechanism of the inner region was a combination of the intergranular and transgranular fractures; however, the primary mechanism was intergranular fracture. The correlations among the binder phase composition, microstructure, and mechanical properties were investigated to determine the gradient structure characterization of the bilayers of the functionally graded cemented carbides.

Influence of Gypsum Binder Phase Composition on Operational and Mechanical Properties of the Hydration Product

The properties of various thermal modifications and forms of calcium sulfate and the conditions of their mutual transition are studied. It is established that the mode of heat treatment of gypsum raw materials affects significantly the nature of the subsequent hydration of the gypsum binder. It is established that the values of pH and pCa suspensions of gypsum binders depend on the temperature of heat treatment of natural gypsum, vary over time and characterize the processes occurring during hydration and hardening of gypsum binders. The values of pH and pCa suspensions of gypsum binders can serve as design criteria for innovative multiphase gypsum binders.

The influence of various Re:Co ratios on microstructures and properties of WC-Co-Re cemented carbides

The WC mean grain size, grains size distribution, binder phase composition and properties of four batches of WC-based cemented carbides with different Co:Re ratios varying from 0:100 to 60:40 were examined. The WC mean grain size significantly decreases, hardness and coercivity increases and magnetic moment decreases when increasing the Re:Co ratio in the binder of WC-Co-Re cemented carbides. The uniformity of the carbide microstructure is slightly reduced by increasing the amount of Re added to the Co-based binder phase. The content of hcp Co in the binder phase steadily increases when increasing the Re content in the binder from 5 to 60 wt% and the Co-Re binder containing 60 wt% Re comprises almost exclusively hcp Co.

Ti(C,N)-Based Cermets: Critical Review of Achievements and Recent Developments

The paper describes briefly the historical development and presents in more detail solid-state properties such as hardness, heat conductivity, thermal expansion and mechanical properties of titanium carbonitride Ti (C,N), the basis of the hard phase of cermets. The metallurgy of Ti (C,N)-based cermets with respect to microstructure formation during sintering and the impact on properties are presented in more detail. The various influences such as W and/or Mo content, Mo/W ratio, C content and C/N ratio, binder phase content and binder phase composition (Co/Ni), sintering time, dwell time, alloy state of powders and grain size were critically evaluated and are presented in form of fracture toughness vs. hardness graphs. A table gives a reference list on the study of these influences. TRS data on cermets were collected and summarised in a separate table, too. The focus is put on grades which have the potential of being fabricated soon in industrial processes for production of cermet tools. Application examples for metal cutting, sawing and chip bonding are presented. In two final sections recent modifications and achievements such as graded microstructures, multicomponent binder, and hybrid microstructures are also briefly presented together with an outlook on the future potential of cermet applications.

Microstructure evolution of WC grains in WC–Co–Ni–Al alloys: Effect of binder phase composition

Abstract In the present work, the microstructure evolution of WC grains in WC–Co–Ni–Al alloys with different Co–Ni–Al binder phase composition, have been investigated. By combination of thermodynamic calculations and decisive experiments, a series of WC–24 wt.% (Co–Ni–Al) alloys were designed and prepared by liquid phase sintering at 1450 °C for 1 h, 8 h and 20 h, respectively. The influence of Ni3Al content in Co–Ni–Al binder on the WC morphology was investigated by scanning electron microscopy (SEM). The results show that, with the increase of Ni3Al content, the increasing interface energy raises both the energy barrier for two-dimensional (2-D) nucleation and the energy barrier for W migration. Under the influence of these two factors, the micro-faceted and stepped planes on the WC grains become more and more obvious and the WC grains become finer and blunter simultaneously. Combining the thermodynamic calculation with the experiment, the mechanism for WC morphology evolution has been revealed. The mechanical properties of the alloys were also discussed.

Grain growth and hardness of TiC-based cermets: Experimental investigation and thermodynamic calculations

In the present work, the influence of Mo and W additions and sintering time on the microstructure, grain growth and hardness of TiC-based cermets was systematically investigated by means of experimental determination and thermodynamic calculations. Under the guidance of the calculated carbon window, the TiC-based cermets with different Mo and W contents have been designed and sintered at 1430°C in Ar atmosphere for 0h, 1h, 2h and 5h. The microstructure of cermets was observed by using scanning electron microscopy (SEM), while the volume fraction and average grain size of ceramic phase were measured by using ImageJ software. The volume fraction of ceramic phase decreases with the addition of Mo and W, which indicates the promoting effect of Mo and W on the carbide dissolution. The grain growth kinetics followed the cubic law, which was controlled by the diffusion of dissolved atoms through liquid binder phase (i.e. Ostwald ripening mechanism). The addition of Mo and W in TiC-based cermets can lead to a slow grain growth process during liquid-phase sintering. In addition, the Vicker hardness measurement was performed for the cermets, and the hardness was influenced by several factors, such as volume fraction and composition of binder phase, average grain size of ceramic phase and bonding strength of interface.

Effect of η-phase and FeAl composition on the mechanical properties of WC–FeAl composites

This study investigated the effects of η-phase generation and the binder phase composition of iron aluminide (FeAl) on the mechanical properties of tungsten carbide–iron aluminide (WC–FeAl) composites. The η-phase was generated in the composites when the WC–FeAl powder was highly oxidized before sintering in a vacuum. The presence of the η-phase resulted in the degradation of mechanical properties such as transverse rupture strength (TRS) and indentation fracture toughness (IFT). In addition, FeAl composition varied mainly as a result of α-Al2O3 formation. The iron-rich side of FeAl in binder phase improved the TRS and IFT. It was concluded that control of the η-phase generation and an appropriate FeAl composition are very important to maintain high TRS and IFT in the WC–FeAl system.

Morphology of TiC Reinforced Ni-Cr-Mo Composite Coatings Prepared by CO<sub>2</sub> Laser

Carbon dioxide (CO2) laser was applied to fabricate TiC reinforced composite coatings. Different microstructures of ceramic phases were observed by SEM. The main phases of coatings were detected by XRD, while the individual one was examined by electron probe X-ray microanalysis .The effect of composition of binder phases on morphology was explained by the ratio of the temperature gradient in front of the liquid/ solid interface to the growth rate.

Influence of Fe–Ni–Co binder composition on nitridation of cemented carbides

Nitridation of cemented carbides leads to the formation of wear resistant Ti(C,N)-enriched outer-surfaces (fcc-rich outer-surfaces). In this work the influence of the binder phase composition on the kinetics of formation of fcc-rich outer-surfaces was investigated. Sintered cemented carbides were nitrided at 1200 °C in a 5 bar N 2 atm for 2 and 4 h. The thickness of the nitrided fcc-rich outer-surfaces increases with the addition of Fe to the Co and Ni binders. Correlations between nitrogen diffusion coefficients and nitrogen solubility levels in Fe–Ni–Co systems are investigated to understand the mechanisms governing the formation of graded layers on nitrided cemented carbides with Fe–Ni–Co binders.

Effect of Adding a Type of Binder Phase on The Microstructure, Properties and Heat Treatment of Steel Bonded TiC Cermets

Particulate TiC reinforced 465 maraging stainless steel matrix Cermets were processed by conventional P/M. The binder phase was added in the form of elemental powders and master alloy powders. The microstructures, binder phase variation with TiC content and mechanical properties were evaluated. The addition of a type of binder phase largely effects the microstructure and mechanical properties. When a master alloy binder phase was used the microstructure showed interphase debondings, microcracks and large growths of TiC particles. Where as, elemental powders in the composition of binder phases showed defect free microstructure of steel bonded cermets. The binder phase variation from starting composition was observed with increase in wt% TiC content and this variation was higher when the master alloy powders were used as a binder. After heat treatment and aging, an increase in hardness was observed. The increase in hardness was attributed to the aging reaction in maraging stainless steel. The response to heat treatment was decreased with an increase in TiC content due to the shift of binder phase from the starting composition.

Quantitative analysis of the effect of the binder phase composition on grain growth in WC-Co sintered materials

Microstructural evolution of WC-Co materials with different compositions and WC grain sizes is discussed from SEM observations and quantitative image analyses of intercept length distributions in the WC phase. Effect of the C/W ratio in the binder phase and of V- or Cr-dopants is particularly studied. Microstructural coarsening is shown to be more rapid and less abnormal when the C/W ratio is increased in the two-phase field {WC + liquid} and up to the three-phase field {WC + C + liquid}. The V-dopant does not completely suppress this effect. The composition dependence of the liquid stability—analysed from the calculated Gibbs energies of the phases—could explain the trend of the experimental results.

Wear behavior and tool life of modified WC-based cemented carbides

The alloy design of WC-10 Co cemented carbides by adding hard phases like TiC/TiN and modifying the binder phase with nickel and molybdenum has been highlighted by the authors elsewhere. The present investigation was aimed at evaluating performance of such cemented carbides in steel cutting. Addition of TiC/TiN improved the crater wear resistance and tool life of WC-10 Co cemented carbide, the improvement being better with TiN additions compared with TiC. Binder phase composition was important in controlling the microstructure and mechanical properties of the tool materials, which had a direct influence on cutting performance. The results were analyzed in terms of microstructure and various properties, viz., hardness, transverse rupture strength, oxidation resistance, and thermal shock resistance, which have a bearing on tool life.

Effects of Carbon Content on Some Properties of WC-10%(Co-Ni) Cemented Carbides

Investigations were made on some fundamental properties of WC-10%(Co-Ni) alloys affected by the carbon content, i.e., the composition of binder phase in the alloys. Specimens were sintered in vacuum at 1375°C for 1.5 hr. Main results obtained were as follows :(1) The composition of binder phase in the alloys showed a marked change in the two phase region as in the cases of WC-Co, WC-Ni alloys, etc., i.e., the amount of tungsten dissolved in binder phase increased sharply with decreasing carbon content and increased also with increasing nickel content in binder phase.(2) Therefore, the properties of the alloys lie between those of WC-Co and WC-Ni alloys, as well as they showed regular changes similar to those in other WC-Co base alloys. It is suggested that the mechanical properties of the alloys containing up to about 10% of nickel in binder are nearly the same as those of WC-Co alloys.(3) With increasing nickel content, the two phase region of the alloys shifted towards the lower carbon side with the extension of that phase region.(4) Summerizing, the WC-(Co-Ni) alloys were confirmed to situate between WC-Co and WC-Ni alloys.

Densification and grain growth during liquid-phase sintering of tungsten-nickel-copper alloys

The kinetics of liquid-phase sintering in tungsten-nickel-copper alloys were examined in the temperature range 1200°–1500°C. The rate constant of the sintering process was evaluated from the volume change as a function of sintering time. The activation energy for the sintering process was about 70 kcal/mole in all three compositions and was independent of the binder phase composition. The average growth of tungsten particles was examined as a function of sintering time in W-3 Ni-8 Cu and W-7 Ni-4 Cu alloys and it was found that mean grain size increased at a rate which was proportional to sintering time, t 1 3 . The activation energy of grain growth was 67 kcal/mole in both systems and is in good agreement with those of 68 kcal/mole determined by the Greenwood's equation and 70 kcal/mole derived for liquid-phase sintering experiments carried out under the same conditions.

WC-TiC-TaC-10%Co合金の諸性質と炭素量との関係

Investigations were made on fundamental properties of various WC-βt-10%Co alloys (βt=WC-TiC-TaC triple carbide phase having definite ratio of 70/30 in WC/TiC) affected by the carbon content, i.e., the binder phase composition. Specimens were vacuum-sintered at 1400°C for 1 hr.Results obtained were as follows: (1) The amount of dissolved W in the γ-phase was considered to be the same as in WC-Co, WC-TaC-Co or WC-TiC-Co alloys; that is, it was in the range of 9∼10% in maximum and 1∼2% in minimum according to the carbon content. Ti and Ta hardly dissolved in the γ-phase. (2) The maximum carbon content in the βt-phase gradually approached the stoichiometric value with increasing tantalum carbide content, and the maximum carbon content reached the stoichio metric value at the content of more than 50∼60%TaC. (3) Hardness and strength of the alloys having the βt-phase with 50∼60%TaC were superior to those of the other alloys. (4) The range of the (WC+βt+γ) three-phase region and the mechanical properties of the alloys were mainly controlled by the titanium carbide content, but not by the tantalum carbide content in the alloys. (5) Magnetic saturation, specific gravity, hardness and lattice parameters of both γ and βt phases showed a change with the carbon content in the alloys.

Relations between Some Properties of Sintered WC-10%Ni Alloy and its Binder Phase Composition

Relations between basic properties of sintered WC-Co base alloys at the room temperature and the composition of the binder phase, that is, the carbon content of the alloys, have been investigated. It was found that the properties were strongly affected by the binder phase composition, although any harmful phase was not formed in-the structures of alloys. On the other hand, researches on the subject for sintered WC-Ni.alloys have never been carried out and it is still vague whether Co is superior to Ni or not as the binder metal of cemented carbides.Therefore, studies on the properties of the WC-10%Ni alloy in relation to the composition of the binder phase were carried out. The results were compared with those already known for WC-10%Co alloy, to get an accurate knowledge on the superiority of Co or Ni as the binder metal. Specimens were vacuum-sintered at mostly 1450°C for lhr. The carbon content of alloys was closely controlled. Results obtained are summarized as follows.(1) Sintering temperature of WC-10%Ni alloy was higher by about 70°C than that of 10%Co alloy. This shows that the temperatures at which the liquid phase is formed, are in this case higher by about 70°C than corresponding temperatures of WC-10%Co two phase alloys. (2) The two phase range in WC-10%Ni alloy extended from about 5.77 to 6.06%C in WC and the width of the range corresponded to about 0.3%C (the values in WC-10%Co alloy are about 6.04-6.22%C and 0.15-0.18%C, respectively). Based on the former result, it is clear that the free carbon phase is formed more easily in Ni-binding alloy than the other. (3) The amount of W dissolved in the binder phase varied abruptly from about 10% to 31% according to the carbon content of the two phase alloys (the value in Co-binding alloy is in the range from 2-3% to 9.10%). (4) Properties such as density, hardness, transverse-rupture strength, magnetic saturation and resistance to acidic solution, etc. showed regular changes in the phase range. These changes were explained by the composition changes in the binder phase. The maximam strength of the alloy was obtained at about the highest carbon side of the range ; however, the value was inferior to that of the Co-binding alloy. The reason may be that the content of the W dissolved in the binder phase in Ni-binding alloy is much higher than that of the other. The alloy having carbon content of less than 5.95% was found to be non-magnetic. (5) Aging phenomena taken place during annealing at temperatures as low as 800°C were not observed in the Ni-binding alloy. (6) The rapid grain growth of WC was observed in the high carbon alloys. (7) From these results, Co was confirmed to be by far superior to Ni as the binder metal of cemented carbides, except for a few cases.

少量のTaCを添加したWC-TaC-10%Co合金の性質について

WC-TaC-10%Co alloys containing 0.5, 1.0, 3.0%TaC (added in the form of a mixed carbide) and having various carbon contents were vacuum-sintered at 1375°C for 2 hr. The particle size of the WC powder used was controlled to obtain an approximately same grain size of carbides in the sintered alloys. Some properties of the as-sintered alloys and the effect of low-temperature annealing (at 800°C up to 50 hr) on them were studied as a function of the TaC and carbon contents, using the experimental method as used in previous investigations(1)∼(4).The main results are as follows: (1) The relations(1)∼(4) recently obtained by the authors on sintered WC-Co straight alloys, namely, that the properties of two phase alloys are remarkably influenced by their carbon contents and also by low temperature annealing when the carbon contents are lower, are substantially maintained in the alloys containing TaC. (2) The composition of binder phase, width and position in the two phase range (a γ+TaC+WC three phase range) of the WC-TaC-10%Co alloys do not change by the addition of TaC. (3) The alloys containing TaC are higher in hardness than the straight alloys, but the strength scarcely decreases. (4) The aging rate at a low temperature is retarded in the alloys containing TaC.