KR19980072305A - Preparation and Forming Method of Titanium / Titanium Carbide Composite Powder by Reaction Milling - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method of producing titanium carbide by the reaction milling method using titanium and activated carbon as a raw powder to produce a titanium / titanium carbide composite powder, and molding the powder using hot compression molding.

2. The technical problem to be solved by the invention

To improve the use of expensive titanium carbide, the problem of high manufacturing cost due to complicated manufacturing process and the inability to obtain excellent mechanical properties.

3. Summary of Solution to Invention

It is solved by the process of synthesizing titanium carbide from the raw powder by the reaction milling method, and by producing the molded body by the vacuum hot compression molding method of the milled powder.

4. Important uses of the invention

Reduced manufacturing cost significantly lowered, and titanium carbide is finely and uniformly dispersed to produce a molded article having excellent mechanical properties.

Description

Preparation and Forming Method of Titanium / Titanium Carbide Composite Powder by Reaction Milling

The present invention is titanium carbide (represented as 'T') and activated carbon (activated carbon) as a raw material by titanium carbide (Reaction Milling) by titanium carbide (hereinafter referred to as 'TiC') The present invention relates to a method of preparing a titanium / titanium carbide composite powder and molding a powder using vacuum hot compression molding.

Titanium composites have high specific strength, excellent corrosion resistance and relatively high temperature characteristics compared to other metals, making them very suitable for use in jet engines, aircraft, machine parts, medical devices, chemical plants and power plants.

As a method of manufacturing the titanium composite material, there are methods such as a composite processing method and a powder metallurgy method. Among them, the composite processing method has a disadvantage in that the manufacturing method is complicated as a method of inserting a composite material into a base material, extruding the bundle, and pulling dozens of the extruded materials into a predetermined form of dies and repeatedly processing them until fine wires are formed.

On the other hand, powder metallurgy is a method of producing a composite by sintering after mixing a titanium alloy powder and titanium carbide particles as a dispersion strengthening element to form a constant shape by cold forming, as shown in Figure 1 (a) Expensive titanium carbide should be used, and as the amount of titanium carbide increases, it is difficult to uniformly mix with the titanium alloy powder, and the formability is sharply degraded. Therefore, it is virtually impossible to manufacture a composite material containing a large amount of titanium carbide.

In order to solve the above problems, the present invention does not require the use of expensive titanium carbide since titanium carbide is synthesized from the raw powder, and solves the problem of high manufacturing cost due to the complicated manufacturing process up to the conventional final product. In addition, an object of the present invention is to provide a titanium / titanium carbide composite powder having excellent mechanical properties by uniformly and finely dispersing titanium carbide having a diameter of 2 to 4 μm and a method of manufacturing the molded article thereof.

This object is a process for synthesizing titanium carbide in-situ using titanium and activated carbon as a raw powder by reaction milling, and molding the milled powder by vacuum hot pressing. It can be achieved by the present invention configured in the step of preparing a bar, will be described in detail with reference to the drawings below.

1 is a manufacturing process of the titanium / titanium carbide powder composite,

(A) is a manufacturing process diagram of the conventional powder metallurgy method,

(B) is a manufacturing process drawing of this invention.

2 is a graph showing the results of X-ray measurement on the phase change of Ti-20vol% TiC composite powder with milling time.

Figure 3 is a graph showing the particle size change of Ti-10vol% TiC, Ti-20vol% TiC and Ti-30vol% TiC composite powder with milling time.

4 shows the shape change of Ti-20vol% TiC composite powder according to milling time: (a) 20 hours, (b) 50 hours, (c) 100 hours, (d) 200 hours, (e) 300 hours, and ( F) Pictures taken in order of 400 hours.

5 is a photograph taken in the order of (A) 1000 ℃, (B) 1200 ℃ and (C) 1400 ℃ of the microstructure change of Ti-20vol% TiC composite according to the molding temperature.

6 is a graph showing the change in relative density of the composite according to the change in the forming temperature and the titanium carbide volume fraction.

7 is a graph showing the change in yield strength of the composite according to the change of the titanium carbide volume fraction in the high temperature compression test at 700 ℃.

Each process which comprises the manufacturing method of this invention is demonstrated in detail below. FIG. 1 (b) shows the steps in the method for producing and forming a titanium / titanium carbide composite powder by reaction milling according to the present invention.

The table below shows the addition amount of titanium powder and activated carbon powder before milling and the chemical composition of the composite powder after milling, so that the volume fraction of titanium carbide produced after milling by stoichiometric calculation is 10, 20, 30 vol%. It was.

[Table 1] Chemical composition of Ti-TiC composite powder before and after milling (wt%)

First, the prepared powders of titanium and activated carbon were loaded into a ball mill vessel at a weight ratio of 1:60 in a ball, and evacuated to a vacuum degree of 2 × 10 ^-3 Torr or more, and then purged twice with argon gas. The gas pressure of was milled at 80 rpm in an atmosphere maintained at 2 × 10 ⁻³ or more.

As can be seen in FIG. 2, the titanium carbide is formed as the milling time is increased, and when the milling time is 200 hours or more, the reaction of the formation of titanium carbide is almost terminated. As shown in FIG. It is possible to produce a titanium / titanium carbide composite powder by ball milling for 200 hours or more, as a fine mixed powder having little difference is produced.

The manufactured composite powder was evacuated for about 1 hour at a temperature of 1000 ° C. or higher using a vacuum hot press molding machine, and then molded by applying a pressure of 20 MPa or more for 1 hour at each temperature, as shown in FIG. 5. Titanium carbide of 2-4 μm is finely dispersed in the titanium matrix, and as shown in FIG. 6, a titanium / titanium carbide composite having a high relative density of 98% or more can be produced. In addition, as shown in FIG. 7, it can be seen that the alloy having TiC of 20 vol% or more has a higher yield strength than the Ti-6Al-4V alloy which is used commercially.

Hereinafter, experimental results on the mechanical properties of the titanium / titanium carbide composite powder and the molded body prepared by the method of manufacturing and forming the titanium / titanium carbide composite powder by the reaction milling according to the present invention, and an enlarged cross section of the titanium / titanium carbide composite. The drawing which posted one photograph is explained in full detail.

FIG. 2 shows the change of phase produced by increasing milling time when milling up to 500 hours in the case of producing Ti-20vol% TiC composite powder using titanium and activated carbon as a raw material powder by X-ray diffraction analysis. It can be seen that the titanium carbide is produced by milling, and since about 200 hours, the diffraction peak of titanium carbide does not change even if the milling time is increased, indicating that the production of titanium carbide is completed.

3 shows the change of the average particle size of the Ti-10vol% TiC, Ti-20vol% TiC and Ti-30vol% TiC composite powder with milling time, and the grain size becomes fine with increasing milling time. It can be seen that after about 200 hours, a powder having a uniform size of 3 to 5 μm can be obtained.

4 shows the shape change of the Ti-20vol% TiC composite powder according to the milling time. As the milling time increases, the irregular powder becomes a spherical powder and almost all powders have a uniform particle size after about 200 hours. It can be seen.

5 shows the change of microstructure according to molding temperature when Ti-20vol% TiC composite powder formed by reaction milling is formed by vacuum hot compression molding method. It can be seen that as the size of titanium carbide increases.

6 shows the change in relative density according to the change in the molding temperature and the volume fraction of titanium carbide, and the relative density gradually increases with increasing molding temperature up to 1200 ° C, and shows a relatively constant relative density after 1200 ° C. Relative density tends to decrease slightly as the volume fraction of titanium carbide increases, but it can be seen that all specimens show excellent moldability of almost 98% relative density.

7 shows the change in yield stress (MPa) after a high temperature compression test for 1 hour at an initial strain of 5 × 10 ⁻³ at 700 ° C. to investigate the mechanical properties of the titanium / titanium carbide composite at high temperatures. It can be seen that the yield strength increases as the volume fraction (vol%) of the titanium carbide increases, and the volume of the titanium carbide is 20 vol% or more when compared with the measurement result of the high temperature compression test of the Ti-6Al-4V alloy. In the case of fractions, it can be seen that the yield strength is higher than that of Ti-6Al-4V alloy.

In the conventional method of manufacturing titanium / titanium carbide composite material using powder metallurgy, various steps such as cold forming by mixing titanium powder and titanium carbide, which are dispersed reinforcement particles, and forming final products by sintering and high temperature isostatic molding are performed. However, the present invention, the manufacturing process is significantly reduced because only two steps of the reaction milling and vacuum hot compression molding, it is possible to significantly reduce the manufacturing cost because it does not use expensive titanium carbide. In addition, it is possible to produce a molded article in which titanium carbide is finely and uniformly dispersed by vacuum hot compression molding.

In addition, the molded article produced by the manufacturing method of the present invention has excellent mechanical properties such as high yield strength and excellent moldability, thereby providing an effective means of development of high temperature Ti alloy.

Claims (2)

Using titanium and activated carbon as the raw material powder, the raw material powder is charged into a ball mill container at a weight ratio of 1:60 and discharged to a vacuum degree of 2 × 10 ^-3 Torr or more, and then purged twice with argon gas. A method for producing a titanium / titanium carbide composite powder by reaction milling, characterized in that it synthesizes titanium carbide by milling at 80 rpm in an atmosphere in which the internal gas pressure is maintained at 2 × 10 ⁻³ or more. Using titanium and activated carbon as the raw material powder, the raw material powder is charged into a ball mill container at a weight ratio of 1:60 and discharged to a vacuum degree of 2 × 10 ^-3 Torr or more, and then purged twice with argon gas. Titanium / titanium carbide composite powder was prepared by milling the internal gas pressure at 80 rpm in an atmosphere maintained at 2 × 10 ⁻³ or more, and the titanium / titanium carbide composite powder was manufactured by using a vacuum hot compression molding apparatus. After exhausting for 1 hour at a temperature of ℃, by applying a pressure of 20MPa for 1 hour at each temperature to form a titanium / titanium carbide composite molded body having a relative density of 98% or more titanium / by reaction milling, characterized in that Forming method of titanium carbide composite powder.