CN101307406A - Molybdenum-free Ti(C,N)-based cermet and preparation method thereof - Google Patents

Abstract

The molybdenum-free Ti(C,N)-based cermet and its preparation method belong to the cermet material. W is used instead of Mo as the auxiliary phase for sintering. The purpose is to reduce the cost of raw materials, and it can be sintered and dense without complicated pre-solid solution method. . In the cermet of the present invention, the final generated phase is Ti(C, N), Ni ₁₇ W ₃ solid solution, wherein W is solid dissolved in Ni, and the weight percentage of each element is: 31≤Ti≤39, 8≤C≤10.5, 2 ≤N≤3, 23≤Ni≤32, 25≤W≤30. The preparation method of the invention comprises the steps of raw material mixing, molding, degreasing and vacuum sintering. The cermet of the present invention has a dense structure, relatively small and uniform hard phase grains; its phase composition is Ti(C, N) and Ni ₁₇ W ₃ , hardness ≥ 88HRA, bending strength ≥ 1700MPa, and impact resistance Well, long life. The preparation method of the present invention does not need to adopt the pre-solid solution technology to prepare TiCN particles first, does not need to improve equipment and technology, and is simple and economical to implement.

Description

Molybdenum-free Ti(C,N)-based cermet and preparation method thereof

technical field

The invention belongs to cermet materials, and in particular relates to a molybdenum-free Ti(C, N)-based cermet and a preparation method thereof, which does not need pre-preparing TiCN particles by pre-solid solution technology.

Background technique

Due to the poor wettability of TiC and Ni in the initial TiC-based cermets, the TiC particles aggregated and grew up during sintering, and the strength and toughness of the material were poor, so its application was limited. In 1956, Henry Ford invented TiC-Mo ₂ C-Ni cermet. After adding Mo or Mo ₂ C to TiC and Ni powder, the wettability of Ni to TiC can be improved, and during the alloy sintering process, (Ti, Mo) C cladding phase is formed around the TiC hard phase particles, inhibiting The growth of TiC particles greatly improves the strength of the cermet. Adding 10% Mo ₂ C can reduce the wetting angle of liquid phase Ni to TiC to zero. The introduction of Mo has epoch-making significance for the development of Ti(C,N)-based cermets, and it is precisely because of the introduction of Mo that this material has been widely used in practical applications. Mo is also considered as an indispensable additive element for Ti(C,N)-based cermets. The existing cermets commonly used in the Japanese market and several cermets being tested in the Chinese market contain Mo, as shown in Table 1 and Table 2. The scanning electron micrograph of the existing molybdenum-containing Ti(C,N)-based cermet is shown in Figure 1.

Mo is mainly used in the production of low-alloy steel, stainless steel, tool steel, carbon steel, alloy steel and super alloys; Mo chemicals are used in the production of petroleum refining, propylene ammoxidation catalysts and aluminum lubricants. In 2004, due to the increase in the international demand for stainless steel and the increase in oil production, the price of Mo ore increased by 50%. Domestically, due to the impact of the West-to-East Gas Transmission Project and the suspension of production at the Huludao Molybdenum Mine in Liaoning, the price of Mo also continued to rise. In the first 10 months of 2005, due to the continuous growth of the global economy, especially the prosperity of the steel industry, the price of Mo has remained high for a long time, and its high price and long duration are rare in history. At present, Ti(C,N)-based cermets containing molybdenum are mainly used in my country's market. Mo is an important raw material for Ti(C,N)-based cermet materials. Finding cheaper raw materials has become an urgent need for market changes. With the improvement of material preparation technology in recent years, TiCN solid solution or TiMCN solid solution with added Ta, Nb and other elements (M is Ta, W, Nb, etc.) , and sintered to prepare molybdenum-free Ti(C,N)-based cermets. When this production process is adopted, Mo is no longer an indispensable component, but it complicates the preparation process.

Table 1 The grades and properties of cermets commonly used in the Japanese market

grade N302 N308 N310 N350 Composition TiCN-WC-TaC TiCN-WC-TaC TiCN-WC-TaC (Ti, W, Ta) CN Hardness (HRA) 91.0～94.0 91.0～92.0 91.0～92.0 92.5 Bending strength/MPa 1200～1400 1600～1800 1700～1900 1700～1900 specific gravity 6.4 7.0 7.0 7.0

Table 2 The grades and properties of several cermets being tested in the Chinese market

grade TN10 TN20 TN30 Composition Ti(CN)-Ni-Mo Ti(CN)-Ni-Mo Ti(CN)-Ni-Mo Hardness (HRA) ≥92.5 ≥91.5 ≥90.5 Bending strength/MPa 1200 ≥1400 ≥1550 specific gravity ≥6.5 ≥6.8 ≥6.8

Contents of the invention

The invention provides a molybdenum-free Ti(C,N)-based cermet material and a preparation method thereof. W is used instead of Mo as a sintering auxiliary phase, the purpose is to reduce the cost of raw materials, and it can be sintered without complicated pre-solid solution method Dense.

A molybdenum-free Ti(C, N)-based cermet of the present invention is made by mixing TiC, TiN, Ni, W, WC and graphite powder through ball milling, molding, degreasing and sintering, and the final generated phase is Ti(C , N), Ni ₁₇ W ₃ solid solution, wherein W is dissolved in Ni, and the weight percentage of each element is: 31≤Ti≤39, 8≤C≤10.5, 2≤N≤3, 23≤Ni≤32, 25≤ W≤30.

The molybdenum-free Ti(C, N)-based cermet is characterized in that the weight percentage of its constituent elements is: 0≤Nb≤2, 0≤Ta≤2.

The preparation method of molybdenum-free Ti(C, N)-based cermet of the present invention comprises the following steps:

1) Mixing of raw materials: mixing TiC, TiN, Ni, W, WC and graphite powder that can meet the weight percentage of the molybdenum-free Ti(C,N)-based cermet composition, and wet grinding with a ball mill;

2) Compression molding: Add 3wt%-8wt% of forming agent polyvinyl alcohol or SBS, and compression molding, the pressure is 150-350MPa;

3) Degreasing: Use a vacuum sintering furnace for degreasing. When the forming agent is polyvinyl alcohol, the degreasing process is: 200°C-400°C, and the holding time is 4-8h; when the forming agent is SBS, the degreasing process is: 300°C-500°C Holding time 4 ~ 8h;

4) Vacuum sintering: the sintering temperature is 1410℃～1450℃, and the holding time is 40～90min.

The method for preparing molybdenum-free Ti(C,N)-based cermets is characterized in that NbC and TaC are added in the raw material mixing step, and the percentage by weight of elements accounting for the total composition of the final product is: 0≤Nb≤2, 0≤ Ta≤2.

The method for preparing molybdenum-free Ti(C,N)-based cermets is characterized in that a planetary ball mill is used in the raw material mixing step, the rotation speed is 100-200 rpm, and the time is 10-36 hours.

The present invention uses W instead of Mo as the sintering auxiliary phase, and can be sintered densely without pre-solid solution method. W and Mo belong to the same group, both have a body-centered cubic structure, have similar properties, and can improve the wettability between TiC and metal phases. Mo can be added in the form of Mo ₂ C or Mo, and W can also be added in two forms of simple substance and carbide. Tungsten has a density of 19.3g/cm ³ and a melting point of 3410°C, both of which are much higher than Mo's density of 10.2g/cm ³ and melting point of 2917°C. The price of Mo is about three times the price of W, and the amount of Mo added when preparing Ti(C,N)-based cermets is 10-25wt%. The use of W instead of Mo significantly reduces the cost of raw materials, and does not affect the preparation process. any negative effects. The diversification of raw materials is more conducive to the further development of Ti(C,N)-based cermets.

In the present invention, since Ni is the active element of W sintering, for 3.3 μm W powder, adding 0.13% Ni can sinter densely at 1300°C; Sintered dense. Molybdenum-free Ti(C,N)-based cermets can be sintered densely at lower temperatures, which are 20°C to 30°C lower than molybdenum-containing Ti(C,N)-based cermets with similar chemical compositions. Since W is easy to react with Ni to form Ni ₁₇ W ₃ , it helps to increase the strength of the binder phase, thereby further improving the comprehensive performance of the material.

Molybdenum-free Ti(C, N)-based cermet structure characteristics of the present invention:

(1) The hard phase grains are uniform in size and regular in shape, as shown in Figure 3.

(2) The microstructure presents a typical core-ring structure, which consists of a white binder phase, a black hard core phase and a gray ring phase. The outer ring is relatively thick, but the inner ring is not complete, as shown in Figure 2 and Figure 4, and the results of energy spectrum analysis are shown in Table 10.

(3) After sintering, the phase composition is Ti(C, N) and Ni ₁₇ W ₃ solid solution, in which W is solid dissolved in Ni, as shown in Figure 5.

The molybdenum-free Ti(C, N)-based cermet of the present invention has a hardness of ≥88.0HRA and a bending strength of ≥1700MPa, and its hardness is slightly lower than that of molybdenum-containing Ti(C, N)-based cermets of similar chemical composition, while its bending resistance The strength is slightly higher than that of molybdenum-containing Ti(C,N)-based cermets with similar chemical composition. This material can be used in any place where molybdenum-containing Ti(C,N)-based cermets with similar chemical composition are used due to its high hardness and flexural strength, chemical stability, and small friction coefficient with metals. . And because this material is more densely sintered than molybdenum-containing Ti(C, N)-based cermets of similar chemical composition, has fewer defects, better impact resistance and longer service life.

The preparation method of molybdenum-free Ti(C, N)-based cermet of the present invention does not need to adopt the pre-solid solution technology to prepare TiCN particles earlier, but directly adopts TiC, TiN, Ni, W, WC and graphite powder sold in the market according to a certain amount. After the chemical ratio is prepared, it can be prepared by ordinary methods; without the need to improve equipment and processes, the implementation is simple and economical, and the performance of the material can be further improved if NbC and TaC are added.

Description of drawings

Fig. 1 is the scanning electron micrograph of existing molybdenum-containing Ti(C, N)-based cermet, with a magnification of 5000;

Figure 2 is a scanning electron micrograph of molybdenum-free Ti(C,N)-based cermets of group C13 in Example 3 of the present invention, with a magnification of 5000;

Fig. 3 is the fracture morphology SEM of C13 group molybdenum-free Ti(C, N)-based cermet in Example 3 of the present invention, with a magnification of 2000;

Fig. 4 is the energy spectrum analysis diagram EDS of the hard phase and annular phase in C13 group molybdenum-free Ti(C, N)-based cermets in Example 3 of the present invention, with a magnification of 5000, and the analysis results are shown in Table 10;

Fig. 5 is the X-ray analysis of the C13 group molybdenum-free Ti(C,N)-based cermet in Example 3 of the present invention.

Detailed ways

Example 1:

Using commercially available TiC, TiN, Ni, W, WC and graphite powders, according to the ingredients of 38.2wt% Ti, 9.5wt% C, 2.3wt% N, 25wt% Ni, and 25wt% W, they were divided into 5 groups, and were wetted by a ball mill. Grinding and mixing materials, the ball-to-material ratio is 5:1 to 7:1, and the process parameters are shown in Table 3.

Table 3 ball milling process parameters

Add 7wt% polyvinyl alcohol as a molding agent to the ground powder, mix and granulate, and adopt compression molding with a unidirectional pressing force of 150 MPa.

The degreasing process is carried out under the condition of a vacuum degree of 5 Pa, the holding temperature is 200° C., and the holding time is 4 hours.

Vacuum sintering is adopted, and the vacuum degree is not lower than 1.0×10 ^-1 Pa. The sintering temperature is 1445°C, and the holding time is 60 minutes; the mechanical properties of each cermet are shown in Table 4.

Table 4 Mechanical properties of various molybdenum-free Ti(C,N)-based cermets

Example 2:

Using TiC, TiN, Ni, W, WC and graphite powder sold in the market, according to the ingredients of 31.9wt% Ti, 8.2wt% C, 2.1wt% N, 28wt% Ni, 29.8wt% W, it is divided into 7 parts B1~B7 Group. Its preparation process parameters are as follows:

The ball milling of the mixture is carried out on a planetary ball mill, the ball-to-material ratio is 5:1-7:1, the rotation speed is 200 rpm, the time is 24 hours, and the milling method is wet milling with ethanol.

The addition amount of forming agent, forming process parameters and degreasing process are shown in Table 5.

Table 5 Addition amount of forming agent, forming process parameters and degreasing process

Vacuum sintering is adopted, and the vacuum degree is not lower than 1.0×10 ^-1 Pa. The sintering temperature is 1420°C, and the holding time is 60 minutes;

The mechanical properties of each cermet are shown in Table 6.

Table 6 Mechanical properties of various molybdenum-free Ti(C,N)-based cermets

Example 3:

The TiC, TiN, Ni, W, WC and graphite powders sold in the market are used, and the ingredients are prepared according to the raw material ratio in Table 7.

Table 7 Composition of various molybdenum-free Ti(C,N)-based cermets

The ball milling of the mixture is carried out on a planetary ball mill, the ball-to-material ratio is 5:1-7:1, the rotation speed is 200 rpm, the time is 24 hours, and the milling method is wet milling with ethanol.

The ground powder is added with 7wt% molding agent SBS, mixed and granulated, and molded with a unidirectional compression force of 200MPa.

The degreasing process is carried out under the condition of a vacuum degree of 5 Pa, the holding temperature is 450° C., and the holding time is 6 hours.

Vacuum sintering is adopted, and the vacuum degree is not lower than 1.0×10 ^-1 Pa. Ni content is different, the sintering temperature is different. Its sintering process is shown in Table 8.

Table 8 Vacuum sintering process parameters

The mechanical properties of each cermet are shown in Table 9.

Table 9 Mechanical properties of various molybdenum-free Ti(C,N)-based cermets

Among them, the scanning electron micrograph of the molybdenum-free Ti(C,N)-based cermet of the C13 group is shown in Figure 2, the SEM of the fracture morphology is shown in Figure 3, and the energy spectrum analysis diagram of the hard phase and ring phase is shown in Figure 4. In the figure, W H: binder phase; H: hard phase; R: annular phase; analysis results are shown in Table 10; X-ray analysis is shown in Figure 5.

Table 10 Element distribution in molybdenum-free Ti(C,N)-based cermet phase

Example 4:

The addition of TaC/NbC is used to further improve performance. The TiC, TiN, Ni, W, WC, TaC, NbC and graphite powders sold in the market were used, and the ingredients were prepared according to the raw material ratio in Table 11.

Table 11 Composition of various molybdenum-free Ti(C,N)-based cermets

The ball milling of the mixture is carried out on a planetary ball mill, the ball-to-material ratio is 5:1-7:1, the rotation speed is 200 rpm, the time is 24 hours, and the milling method is wet milling with ethanol.

The ground powder is added with 7wt% molding agent SBS, mixed and granulated, and molded with a unidirectional compression force of 200MPa.

The degreasing process is carried out under the condition of a vacuum degree of 5 Pa, the holding temperature is 450° C., and the holding time is 6 hours.

Vacuum sintering is adopted, and the vacuum degree is not lower than 1.0×10 ^-1 Pa. The sintering temperature of D1, D2, and D3 is 1435°C, and the holding time is 60 minutes; the sintering temperature of D4 is 1430°C, and the holding time is 60 minutes; the sintering temperature of D5 and D6 is 1415°C, and the holding time is 60 minutes;

The mechanical properties of Ti(C,N)-based cermets prepared by using these components and methods are shown in Table 12.

Table 12 Mechanical properties of various molybdenum-free Ti(C,N)-based cermets

Claims (5)

1. A molybdenum free Ti (C, N) based ceramic metal are made TiC, TiN, Ni, W, WC and powdered graphite through ball mill mixing, moulding, degreasing and sintering, final generate be mutually Ti (C, N), Ni ₁₇W ₃Sosoloid, wherein the W solid solution is in Ni, and each element wt per-cent is: 31≤Ti≤39,8≤C≤10.5,2≤N≤3,23≤Ni≤32,25≤W≤30.
2. 2. (C, N) based ceramic metal is characterized in that in its composition element wt per-cent: 0≤Nb≤2,0≤Ta≤2 molybdenum free Ti as claimed in claim 1.
3. 3. (C, N) preparation method of based ceramic metal comprises the steps: the described molybdenum free Ti of claim 1

   1) raw material mixes: (the employing ball mill carries out wet-milling for C, N) TiC of based ceramic metal composition weight percent, TiN, Ni, W, WC and powdered graphite mixing to satisfy described molybdenum free Ti;

   2) compression molding: add forming agent polyvinyl alcohol or the SBS of 3wt%-8wt%, compression molding, pressure is 150～350MPa;

   3) degreasing: adopt vacuum sintering furnace to carry out degreasing, when forming agent was polyvinyl alcohol, degreasing process was: 200 ℃～400 ℃, and soaking time 4～8h; When forming agent was SBS, degreasing process was: 300 ℃～500 ℃ soaking time 4～8h;

   4) vacuum sintering: 1410 ℃～1450 ℃ of sintering temperatures, soaking time 40～90min.
4. 4. (C, the N) preparation method of based ceramic metal is characterized in that adding NbC, TaC in the described raw material mixing step molybdenum free Ti as claimed in claim 3, account for the total composition element wt of final product per-cent to be: 0≤Nb≤2,0≤Ta≤2.
5. 5. (C, the N) preparation method of based ceramic metal is characterized in that adopting planetary ball mill in the described raw material mixing step, and rotating speed is 100～200rpm, and the time is 10～36h as claim 3 or 4 described molybdenum free Tis.

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