KR20160088170A

KR20160088170A - TiC-FeAl HARD MATERIALS AND FABRICATING METHOD FOR THE SAME

Info

Publication number: KR20160088170A
Application number: KR1020150007575A
Authority: KR
Inventors: 손인진; 송주환
Original assignee: 전북대학교산학협력단
Priority date: 2015-01-15
Filing date: 2015-01-15
Publication date: 2016-07-25

Abstract

The present invention relates to a nanostructured TiC-FeAl carbide material, which is a structure in which a hard substrate is bonded to a hard substrate by sintering a nano powder, the hard substrate is a TiC material, and the binder phase is FeAl do.
The present invention has the effect of lowering the cost, increasing the hardness, and excelling in corrosion resistance by sintering the TiC nano powder using FeAl as a binder.
In addition, the TiC-FeAl carbide material of the present invention is produced by sintering nano-powdered TiC and FeAl with heat generated by applying a pulse current, so that crystal grain growth of TiC is limited and excellent mechanical properties and oxidation resistance are obtained.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a TiC-FeAl carbide material,

More particularly, the present invention relates to a nanostructured TiC-FeAl carbide material and a manufacturing method thereof.

Carbide materials are generally used for cutting tools, drawing dies, molds, nozzles, and the like as material materials having a very high hardness. Tungsten carbide and titanium carbide (TiC) are widely known as materials for carbide, and Co or Ni is used as a binder in molding and processing. However, since Co and Ni are not only poor in corrosion resistance but also high in price, currently used cemented carbide materials are limited in their use range.

In addition, at present, a product is manufactured by heating and sintering at a temperature of about 1300 ° C or higher for 1 hour or more in the course of manufacturing an article using a cemented carbide material. This method is disadvantageous in that it is expensive to manufacture because it is manufactured at a high temperature and for a long time. Further, the TiC crystal grains grow during the process of pressurizing and sintering by heating at a high temperature for a long time, and the grain size of the metal carbide is increased, and the mechanical properties are deteriorated.

Therefore, there is a high demand for a new binder which is inexpensive, has a high hardness, is excellent in corrosion resistance, and can be sintered at a low temperature in a short time.

It is an object of the present invention to provide a cemented carbide material which is low in cost, high in hardness, excellent in corrosion resistance, and capable of performing a sintering process at a low temperature in a short time, and a method of manufacturing the same. .

In order to achieve the above object, the nano-structured TiC-FeAl cemented carbide according to the present invention has a structure in which a hard substrate is bonded to a binder by sintering a nano powder, the hard substrate is a TiC material, .

At this time, when the crystal grain of the TiC substrate is 100 nm or less, it has excellent mechanical properties and oxidation resistance. The volume ratio of FeAl is preferably greater than 0 vol% and not greater than 95 vol%.

According to another aspect of the present invention, there is provided a method for manufacturing a nano-structured TiC-FeAl cemented carbide material, comprising: (S1) preparing TiC and FeAl raw material powders; Milling TiC and FeAl raw material powders together to form nano-sized powders so as to have a nano-sized particle size (S2); (S3) press molding and sintering while applying heat generated by a pulse current to the mixed nano powder in the step (S2); And (S4) shutting off the current when the shrinkage length of the nano powder is not changed in the step (S3) and cooling the press-molded and sintered nanostructure to room temperature just before the current interruption.

The nano-pulverization in step S2 is preferably carried out by pulverizing the TiC and FeAl so that the particle size thereof is 100 nm or less and performing dry ball milling.

The pressure molding and sintering in step S3 is preferably performed for 2 to 30 minutes, and it is preferable that the period of the pulse current is in the range of 1 mu s to 1 ms and the heating rate by the pulse current is in the range of 100 to 5000 DEG C / min .

The pressure molding in step S3 is carried out under a pressure of 0 to 1000 MPa, preferably in a vacuum state of 0.01 to 1 Torr or an inert atmosphere.

It is preferable that the observation of the shrinkage length change of the nano powder in step S4 is performed by a linear displacement differential transformer (LVDT).

It is preferable that the FeAl powder is mixed so as to be greater than 0 vol% and equal to or less than 95 vol% in the step (S1).

The present invention constructed as described above has an advantage of being low in cost, high in hardness and excellent in corrosion resistance by sintering TiC nano powder using FeAl as a binder.

In addition, the TiC-FeAl carbide material of the present invention is produced by sintering nano-powdered TiC and FeAl with heat generated by applying a pulse current, so that crystal grain growth of TiC is limited and excellent mechanical properties and oxidation resistance are obtained.

1 is a schematic diagram showing a die assembly of a pulse current sintering machine used in this embodiment.
2 is a graph showing temperature changes and contraction displacement with heating time by pulse current heating / pressure sintering in this embodiment.
FIGS. 3 and 4 are FE-SEM photographs of specimens produced by pulse current heating / pressure sintering of this embodiment.
5 and 6 are XRD analysis results of the specimen produced by the pulse current heating / pressure sintering of this embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the accompanying drawings, embodiments of the present invention will be described in detail.

The nano-structured TiC-FeAl carbide material of the present invention is a structure in which a substrate of TiC originating from a nano-sized powder is bonded by a binder of a FeAl material. At this time, the volume ratio of FeAl as a binder phase is preferably greater than 0 vol% and not greater than 95 vol%. The FeAl used as the binder in the present invention is excellent in the characteristics of the cemented carbide material compared to the case of using a binder of different material because it is inexpensive, has a high hardness, and is excellent in corrosion resistance. In particular, since the TiC-FeAl carbide material of the present invention is produced by sintering a nano-sized powder and the sintering process using FeAl is performed at a relatively low temperature for a short time, the crystal grains of the TiC substrate are controlled to be 100 nm or less It has very good mechanical properties and oxidation resistance due to fine TiC grains.

The method for manufacturing a nano-structured TiC-FeAl cemented carbide according to the present invention comprises the steps of preparing a raw material powder of TiC and FeAl (S1), ball milling a raw material powder of TiC and FeAl together to form a nano- (S2), a step (S3) of press molding and sintering while applying heat generated by a pulse current to the mixed nano powder in step (S2), and a step (S3) of interrupting the current and pressurizing and sintering And cooling the nanostructure to room temperature (S4).

In step S1, TiC powder constituting the cemented carbide material and FeAl powder serving as the binder are prepared. The smaller the size of the TiC powder, the better the physical properties of the prepared cemented carbide material. However, the size of the powder is not limited because the process of making the nano powder is separately performed in this embodiment. At this time, the amount of FeAl powder mixed in the TiC powder is more than 0 vol% and not more than 95 vol%.

Next, in step S2, the nano powder is mixed while performing the nano-powdering to make the size of the raw material powder into the nano size. When the size of the powder is adjusted to a nano size of 100 nm or less, the physical properties of the cemented carbide material are improved and the sintering speed is increased. The ball milling method is suitable for nano-sizing the powder because of sufficient energy applied at the time of milling, and it is possible to obtain an effect of evenly mixing the raw powder. The ball milling is preferably carried out by dry ball milling in an inert gas atmosphere.

In step S3, sintering is performed using heat generated by applying a pulse current to the nanoized raw material powder.

1 is a schematic diagram showing a die assembly of a pulse current sintering machine used in this embodiment.

The die assembly 200 of the pulse current sintering machine for sintering the raw material powder according to the present embodiment includes upper and lower punches 210 of a high purity graphite material and upper and lower pressurizing portions of an insulating material such as a cylindrical die 220 and alumina Block 230. < / RTI > The raw powder is placed in the center space of the cylindrical die 220 and the punch 210 connected to the pressing block 230 is inserted above and below the space filled with the raw powder. The pulse current supply device 300 is operated by a control switch 310 and applies a pulse current to the raw material powder through the punch 210. The pressurizing block 230 transfers the pressure of the pressurizing device to the punch 210 to apply uniaxial pressure to the raw powder. At this time, a linear displacement differential transformer (LVDT) is attached to the movable part of the hydraulic cylinder included in the pressurizing device to measure the length change of the specimen during the sintering process.

The sintering process is not necessarily performed in a vacuum state, but is preferably performed in a vacuum state in the range of 0.01 to 1 torr. The pressure applied to the punch 210 is preferably in the range of 10 to 1000 MPa, and a pressure sufficient to sufficiently densify the specimen is experimentally determined and applied. The period of the pulse current is preferably in the range of 1 mu s to 1 ms, and is applied until sintering proceeds and densification of the specimen occurs. The heating rate by the pulse current is preferably controlled in the range of 100 to 5000 占 폚 / min. On the other hand, a conventional rotary pump, a cooling water pump, or the like can be used as a vacuum device and a cooling device for vacuum processing the cylindrical die 220. The control and measurement device controls process parameters such as pressure and current, Measure various data in progress.

Hereinafter, results of analyzing the characteristics of the specimen according to the embodiment will be described. The following examples are provided to aid understanding of the present invention and are not intended to limit the present invention to the following examples.

TiC powder having a particle size of 1.4 占 퐉 is added to each of the TiC powder so that the content of FeAl is 5vol% and 10vol%, respectively, to prepare 20g of raw material powder. The prepared raw material powder was ball-milled and pulverized to have an average particle diameter of 30 nm.

The nano-powdered raw material powder was charged into a pulsed current sintering machine of FIG. 2, and then a vacuum atmosphere of 0.04 torr was prepared. With the uniaxial pressure of 80 MPa applied to the raw material powder, pulsed current was applied to the raw material powder and Joule heat was applied at a heating rate of 1100 캜 / min.

During the sintering process after the initiation of heating / pressing, the shrinkage length of the specimen was observed with a linear displacement differential transformer (LVDT). At the point of stabilization without any change in length, the pulse current and pressure were removed, TiC-FeAl cemented carbide material.

On the other hand, for comparison, a cemented carbide material was obtained under the same conditions using TiC powder not mixed with FeAl.

In the above examples, the TiC-FeAl raw material powder was subjected to ball milling, and then the temperature and shrinkage length changes, SEM (Scanning Electron Microscope) photographs and XRD (X) images before and after pulse current heating / pressure sintering and pulse current heating / -ray diffraction patterns are shown in Figs. 2 to 6, respectively.

2 is a graph showing temperature changes and contraction displacement with heating time by pulse current heating / pressure sintering in this embodiment.

According to the temperature change (2) and the shrinkage displacement (DELTA O) in FIG. 2, when the pulse current heating / pressure sintering method of this embodiment is applied, the shrinkage length change is relatively short at a relatively low temperature of 1300 DEG C within 2 minutes TiC-FeAl carbide materials were produced.

FIGS. 3 and 4 are FE-SEM photographs of specimens produced by pulse current heating / pressure sintering of this embodiment.

FIG. 3 is a photograph of a TiC-5vol% FeAl carbide material, and FIG. 4 is a photograph of a TiC-10vol% FeAl carbide material. As shown in the figure, it can be confirmed that a TiC-FeAl carbide material having a dense nano structure with almost no pores is produced.

5 and 6 are XRD analysis results of the specimen produced by the pulse current heating / pressure sintering of this embodiment.

Figure 5 shows the results for TiC-5vol% FeAl carbide materials, and Figure 6 shows the results for TiC-10vol% FeAl carbide materials. As shown, a peak for TiC was observed and the size of the grain identified from the half-width of this diffraction peak was about 100 nm, from which the desired nanostructured TiC-FeAl carbide material was obtained by pulse current heating / pressure sintering It was confirmed that it was manufactured.

The hardness and fracture toughness of the TiC-5vol% FeAl and TiC-10vol% FeAl carbide materials prepared according to this example were measured by other researchers [Ref. 1. I.J. Shon, I.K. Jeong, I.Y. Ko, J.M. Doh, K.D. Woo, Ceramics International 35, 339 (2009)].

BINd content
(vol%) relative density
(%) grain size
(nm) Hv
(Kg / mm ² ) K _IC
(MPam ^1/2 )
Comparative Example
10 Co 98 61 1780 8.3 10 Ni 98 44 1822 8.6 10 Fe 99.9 80 1905 8.5 Example 5 FeAl 99 63 2390 8 10 FeAl 100 120 2180 11

TiC-5vol% FeAl carbide material and TiC-10vol% FeAl carbide material Hardness and fracture toughness were respectively 2390, 2180㎏ / ㎜ ² and 8, 11 ㎫.m ^1/2. These results show that the fracture toughness is similar or improved and the hardness is greatly increased as compared with the cemented carbide material of the comparative example using Co, Ni or Fe. And since the price of FeAl is half the price of Co or Ni, the manufacturing cost is greatly reduced.

While the present invention has been particularly shown and described with reference to preferred embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Those skilled in the art will understand. Therefore, the scope of protection of the present invention should be construed not only in the specific embodiments but also in the scope of claims, and all technical ideas within the scope of the same shall be construed as being included in the scope of the present invention.

200: die assembly 210: punch
220: Cylinder die 230: Press block
300: Pulse current supply 310: Control switch

Claims

A structure in which a hard substrate is bonded to the binder by sintering the nano powder,
Wherein the hard substrate is a TiC material, and the binder phase is FeAl material.

The method according to claim 1,
Wherein the TiC substrate has a grain size of 100 nm or less.

The method according to claim 1,
Wherein the FeAl volume ratio is greater than 0 vol% and not greater than 95 vol%.

The method according to claim 1,
Wherein said carbide material is made by pulse-current activated sintering. &Lt; RTI ID = 0.0 > 11. < / RTI >

Preparing a raw material powder of TiC and FeAl (S1);
Milling TiC and FeAl raw material powders together to form nano-sized powders so as to have a nano-sized particle size (S2);
(S3) press molding and sintering while applying heat generated by a pulse current to the mixed nano powder in the step (S2); And
(S4) of shutting off the current when no shrinkage length of the nano powder is changed in the step (S3), and cooling the pressed and sintered nanostructure to room temperature until immediately before current interruption. Method for manufacturing FeAl carbide material.

The method of claim 5,
Wherein the nano-powdering in the step (S2) is performed such that the particle size of TiC and FeAl is 100 nm or less.

The method of claim 5,
Wherein the pressing and sintering in the step (S3) is performed for 2 to 30 minutes.

The method of claim 5,
Wherein the period of the pulse current in the step (S3) is in the range of 1 mu s to 1 ms.

The method of claim 5,
Wherein the heating rate by the pulse current in the step (S3) is in the range of 100 to 5000 占 폚 / min.

The method of claim 5,
Wherein the pressure molding in the step (S3) is performed by applying a pressure of 0 to 1000 MPa.

The method of claim 5,
Wherein the pressing and sintering in the step (S3) is performed in a vacuum state of 0.01 to 1 Torr or an inert atmosphere.

The method of claim 5,
Wherein the observation of the shrinkage length change of the nano powder in the step (S4) is performed by a linear displacement differential transformer (LVDT).

The method of claim 5,
Wherein the FeAl powder is mixed in an amount greater than 0 vol% and less than 95 vol% in the step (S1).

The method of claim 5,
Wherein the ball milling in the step (S2) is performed by dry ball milling.