Phase Transformation of WC-Co Carbide γ Phase

Stomach, hate 0, 7 phase transition of hard alloy Liu Shourong Tianjin Carbide Research Institute. The phase transformation of Tianjin 3,222 solid solution phase transition cemented carbide during the cooling process from room temperature to room temperature is mainly carried out by a diffusion type mechanism. The non-diffusion type transition point is above room temperature and close to room temperature at room temperature. There is little 1 in the alloy. Below the private point, the factors that cause the stress in the alloy to increase or loosen between the 0 phase and the 7 phase increase or decrease, causing the increase in the proportion of 07 in the 7 phase of the alloy.

Sintering was carried out in an atmosphere of 2 gas or dissociated ammonia and in vacuum, respectively, to prepare samples of alloys. Rare earth oxide mixed rare earth additives for the preparation of rare earth added 10 alloy samples in the molybdenum furnace gas outlet protection or high frequency heating to 0,1 heat 10 heat bonfire heat treatment, in the liquid, to maintain 10,1001! Conduct deep 7 orders. Prepared by machine, etching alternating polishing method, X-ray diffraction analysis of alloy specimens, 1D diffractometer to determine phase composition and surface macroscopic stress 2 results of the alloy sample and analysis of type and type of mixed media of the two structures, but usually 7 The proportion of the phase is small. With the increase of the nominal cobalt content in the alloy, the amount of 7-phase mass fraction in the phase content can reach 7 phases. The phase is stable. Grinding or crushing the carbide sample at room temperature can lead to the sample layer or the whole. 17 Significantly increase the ratio of the cooling rate from the sintering temperature to room temperature and the quenching temperature above room temperature can reduce the bounds, the ratio of the alloy 7 and the medium 7 phase 8 Tianjin natural science fund project; Received date 19981217; Liu Shourong . male. Born in 1939, Senior Engineer; Contact Information, Tianjin Cemented Carbide Research Institute Materials Science, Cemented Carbide 7 Phase Structures and Phase Transformations Jia 0 Alloys 7-Phase Content at Room Temperature is Significantly High by Up to 4 The authors believe that high cobalt content In the alloy, a lower ratio of 1.71 for the cobalt alloy is; for example, the foot, that is, rent, etc., 1 is said to be sintered. The 7 phases in the 20 alloy are all 0. Type 5, 12 is considered to be a mountain. The mechanical restraining effect of the rigid skeleton on the phase caused the gold to be mediated. 7 increase stability. Thus the chamber; Alloy 7 phase is. Type, 13, plus, etc., consider that the solidity of Yuwu in Xinzhan; and the decrease of the thermodynamic stability of cobalt cause it. , The transformation of the temperature of the high-corpse pure drill. Close to 1 but the solidification of tungsten in cobalt has made its non-diffusion type transition temperature from 8 o'clock below room temperature, Si 03;

For calcination 10, 7 phases in alloy cooling process 1.1.

Phase transition, more research results are discussed by the non-diffusion type enthalpy transformation mechanism, and the 7th phase transition in temperature is also mainly analyzed by the method of crystallization geometry. 43. This paper proposes that, at room temperature and above, the phase of alloy cooling is 7 phases. The diffusion-based transition is mainly used and analyzed and discussed from the perspective of thermodynamics.

1 Experimental method examples, but whether the slow cooling or quenching of the sample, the 7 phase at room temperature is 7 phase sum. There is no critical cooling rate for the 7-phase transitions of the 7-phase complexes at high temperatures. The cryogenic treatment below room temperature can significantly increase the 7-phase content of the 8 alloys. Quenching treatment and cryogenic treatment can significantly improve the evaluation, the surface of the alloy sample macroscopic compressive stress 1.

In the wire-cutting surface 1 of the cemented carbide and on the surface where the laser is exposed. Almost all of the 7-phases are of the type, and the addition of rare earths to 0. The microstructure of the cemented carbide at room temperature 7 phase has little influence on the structure, but it can obviously increase the surface compressive stress of the hard alloy samples.

Diffraction angle plus 8, carbide, 1. Spectrum diffraction angle 26 diffraction angle 20.

3 Discussion 3. Thermodynamic analysis of 7 phase transition of cemented carbide. The six gold specimens were during the hailfall from stilts to trials.

Buckle 77 phase transition + critical cooling rate. The neophase 7 phase + is a metastable phase, but is stable, and the new phase 7 phase and the mother phase, there is a clear compositional change between the phase and the martensitic transformation characteristics are completely undefective, so the 17 phase transition at the temperature change should be quasi-extended. goods.

The 7-phase structure of cemented carbide and the change of phase transition from pure cobalt to cobalt and the cooling process from the as-sintered state to room temperature resulted in the induction of 7-transformation due to the internal stress between the yttrium phases. The amount of phase. When the alloy sample is slowly cooled from the sintering temperature, tungsten and carbon atoms are dissolved by diffusion from the 17 phase to maintain the thermodynamic equilibrium state of the 7 phase. 71.7+., Ice 1 Ge, 7-phase internal energy. 1 When the concentration of the crane increases, it is in a thermodynamic equilibrium state and the 7-phase free energy is 7 phases higher. However, drilling. 1 drill the same composition. Therefore, at the same temperature, the free energy difference between phase and 17 phase should be higher than the internal energy difference between cobalt and 1 diamond. This shows that the solid solution of tungsten in cobalt forms 7 phases, which reduces the thermodynamic stability, 1! In order to expand the style, 717 ten. The initial transition temperature of the Tan should be higher than the initial temperature of the cobalt station transformation is about 427, which is due to the close relationship of the initial transition temperature of 7.7 provided by the 5, as the result of tungsten in the 7 phase. The diffusion rate is very slow. For example, 1 and 3 think that the proliferation of inhibitors must be carried out. Therefore, the 17-phase quantities produced by the high-temperature equilibrium transformation by means of expansion methods are very small.

At low temperature, tungsten atoms are difficult to diffuse, 7 phase can only take non-expansion, mode 迸疔 transformation, the tungsten content in the product phase is supersaturated, tungsten atoms will be caused in addition to the substitution in the cobalt crystal lattice The symmetry of the cobalt lattice changes 3. In this way, compared with the equilibrium state, the internal energy of the low-temperature 07 phase is lower than that of the equilibrium, and the difference between the self-energy of the 7-phase and the 7-phase is higher than that of the same-temperature 1 cobalt and cobalt. The difference is low. Caused by the low temperature 7 phase from the transition point lower than pure cobalt.

It is difficult to perform 7-phase transformation by diffusion of tungsten atoms at room temperature, but grinding or grinding at elevated temperature can significantly increase the ratio of 4 samples or 1 in the entire sample compared to carbide samples, indicating that 7 phases are not diffused. Phase change results. Therefore, the 7-phase transition point should not be lower than the room temperature, which is the pseudo-element provided by 80, etc., which is the boundary of the alloy in the phase of the alloy. The 1 point of the gold phase 7 is below the room temperature. The result is different.

In summary, the first phase of burning thorium, the 7 phase transition of cemented carbide is described as 71 point to room temperature equilibrium transition 17 near equilibrium state, and the desolvent process such as 7 near equilibrium state of sintering state Jia 00 alloy at room temperature 7 phases from the residue 7 non-equilibrium. 17 and nearly 71.1. Considering the desolvation of tungsten from the 7 phase in the cooling process, the order of the solid solubility of tungsten in the 7 phase is the order of the first birth, 7 the residual 7 mountain 1 welcomes the expansion, the 17 phases of the mode change are few, plus 7 The phase from the point close to room temperature, in the absence of additional deformation induced stress, 7 phase is very slight, low temperature tempering, 7 phase total amount of small change is stable and called 1 compared to 17 cases. Therefore, the proportion of 7-phase ratio of sintered-grain 0 cemented carbide at room temperature 7 phase passes 3.2 Internal stress on the impact of phase transformation of cemented carbide The phase-expansion coefficient of the phase is 3.840 far away from the household 7 phases 1.27 Plant 5 due to the milk, the alloy Microscopic internal stress is generated between the phases and the phases during cooling from the sintering temperature to room temperature. The 7-phase is subjected to tensile stress, and the phases are subjected to 吒 stress.

This internal stress can be exacerbated with cold, plus or quenched, although 7-phase is followed. Type transformation mechanism 13, the production of the internal stress 1 should affect the transformation process of the 7 phase, but the internal stress in the alloy is mainly formed during the cooling process above the enthalpy point, while the boundary center and the metal phase recognition Point, near room temperature. Therefore, this internal stress has little effect on the 7-phase transformation above room temperature. However, the increase in the cold or the ocean is often small.

The desolvation process can thus suppress the 7-phase diffusion-type phase transition, resulting in a higher tungsten concentration in the room temperature 7 phase compared to a lesser 17 phase. The cryogenic treatment at the 7 o'clock temperature into the hall resulted in +7 phases and the supersaturation of the tungsten concentration in the phase was exacerbated. The free energy difference between the 7 and 7 phases was very poor and the cooling rate was extremely high. The internal stress between phase 1 and phase 7 is increased and thus 7 phases are induced. During the cryogenic treatment, there is no restraining effect of the 10 skeleton to 7 phase transition. On the contrary, due to the deep cryogenic treatment, the increase of the internal stress between the framework and the seven phases initiates the transformation of the seven phases. The electrolysis method selects the corrosion and the phase of the corrosion process will relax the phase and the phase between the seven phases in the sintered alloy. The intrinsic internal stress state inevitably induces a 7-phase Yao transformation, resulting in a 17-phase higher than the 7-phase content inherent in the as-sintered alloy. This should be due to the fact that many domestic authors use electrolytic corrosion to separate the boundary and 7 phases. The preparation of the sample results in a relatively high 17 in the test results. The condition of the variable is not the constraint of the mechanical stress in the alloy sample, but the internal stress is strengthened or relaxed. The state of the process will induce a phase change machine, 3.3 Cobalt content on the boundary, the impact of cemented carbide 7 phase change 槲 spat, 9 of the study, due to it, the Department. The tungsten diffusion process proceeds very slowly during the cooling process of the gold self-sintering temperature. Therefore, the precipitation of the tungsten atoms from the 7-phase and the precipitation on the adjacent 1 grains causes the gradient of the tungsten concentration in the 7-phase to be distributed in the JIA grain. The tin concentration is very low in the 7 phase in the range of about 0. The 7-phase layer in the low-cobalt content disperse alloy is extremely thin, and the 7-layer thickness of the 18 alloy layer is usually less than 3 in the coarse grain size grade. This bit may be slightly higher. That is, almost all of the above-mentioned low tungsten concentration 7 phase range. It shows that the low cobalt content of Ca 0, the tungsten atoms in the alloy 7 phase is easily precipitated on the adjacent 1 grain through the diffusion method during the cooling process of the alloy at the sintering temperature, resulting in the higher concentration of tungsten in the 7-phase tungsten alloy. According to the above discussion about the effect of tungsten concentration in the phase on the 7-phase slip point, and the phase 3, the low-drilling amount of the alloy 7 phase should be slightly higher. In the alloy cooling process, there is a higher chance of private transformation of the 7 phase at the spot temperature below the higher cobalt alloy, so the low cobalt content alloy at room temperature is slightly higher than the 17 at the higher cobalt alloy. In addition, the high cobalt content in the low-cobalt-content alloy has a large volume fraction, and thus the induction of the 7-phase higher cobalt alloy is more.

3.4 Effect of other processing on the phase transformation of 0 and 7 alloys. In addition to decreasing the tungsten concentration in the 7 phase, the rare earth element of cemented carbide can significantly change the internal stress state in the alloy. Therefore, adding rare earth contributes to the sail 0, alloys. 7-phase transition. However, according to the 7-phase 4 transformation machine, the dissolved rare earth 71 in the 7 phase of the 7 phase can not only improve the 7-phase stacking fault energy of the 7-phase original blank nuclei, but also have the effect of suppressing the 7-phase transformation, and it can also weaken the internal stress changes. The induced plastic deformation has the ability to induce the transformation of 7 phases. Therefore, the two opposite effects of rare earth elements on the 7-phase transformation determine that the rare earth has little effect on the 7-phase transformation.

After being subjected to wire cutting and laser processing, the 7-phase of the alloy product surface is melted and concentrated, and the primary-phase-free phase formed during the subsequent rapid cooling process is rapidly cooled to room temperature and diffusion-type phase transformation is difficult. Therefore, the 7 phases of the alloy sample treated surface subjected to the wire cutting process and the laser process are substantially maintained in the type structure.

4 Conclusions Sintering state 0, the room temperature 7 phase of cemented carbide is usually a combination of both structural and structural variants. However, the 17 phase ratio is very small. During the cooling process from the sintering temperature to the room temperature, the phase transition of 0, the cemented carbide 7 phase is mainly diffusion type, and its diffusion type enthalpy transition point is above room temperature and close to it. Room temperature.

Below the seven-phase defect temperature, any art process that causes the stress change between 0 and 7 phases in hardened carbides to strengthen or relax can all lead to a life ratio of 71.71, Liu Shourong 100, and cemented carbide 7 phase. Change 2 period 8 Liu Shourong, Liu Fang. Journal of Metal Heat Treatment, 1997, 18457 10 Liu Shourong, Liang Fuqi et al. Chinese Journal of Rare Earths, 1998, 161