JPH0372058A - Structural member made of titanium or titanium alloy - Google Patents

Abstract

PURPOSE:To modify a metallic structure and to provide a structural member which has a surface layer part having superior sliding characteristics and strength by providing a surface layer part modified by means of local melting alloying treatment by the use of a high-density energy source and constituting the above surface layer part of specific two phases. CONSTITUTION:This structural member 10 consisting of titanium or titanium alloy has a surface layer part 3 modified by means of local melting alloying treatment by the use of a high-density energy source, such as carbon dioxide laser. Further, this surface layer part has a metallic structure in which a primary beta phase containing complete solid solution type beta stabilizers and a secondary beta phase containing eutectoid type beta stabilizers. Since the metallic structure in this surface layer part is fine and homogeneous and is a mixed structure of two beta phases, sliding characteristics in the surface layer part is remarkably improved. Moreover, this surface layer part has high strength and high adhesive strength to a base material.

Description

[Detailed description of the invention] A1 Purpose of the invention (1) Industrial application field The present invention relates to structural members made of titanium or titanium alloys.

(2) Prior Art Conventionally, as this type of structural member, there has been known a structural member in which the parts requiring sliding properties are made of a molten β-type titanium alloy whose metal structure is a single β phase ( Japanese Unexamined Patent Publication No. 61-24
(See Publication No. 7806).

(3) Problems to be Solved by the Invention However, the forged β-type titanium alloy has somewhat improved sliding properties compared to the ingot-produced α-type and α+β-type titanium alloys. It is not possible to satisfy the required sliding characteristics of the structural members used.

In view of the above, an object of the present invention is to provide a titanium or titanium alloy structural member having a surface layer portion having excellent sliding properties and strength by modifying the metal structure.

B1 Structure of the Invention (1) Means for Solving the Problems The titanium or titanium alloy structural member according to the present invention includes a surface layer portion modified by a local melting process using a high-density energy source. The metallographic structure of the surface layer is composed of a mixture of two phases: a first β phase containing a total solid solution β stabilizing element and a second β phase containing a eutectoid β stabilizing element. It is characterized by being

(2) Effect When the above-mentioned local melting alloying process is applied, a rapid solidification effect due to self-cooling of the melt diameter is obtained, so the metal structure in the surface layer becomes fine and homogeneous, and the surface layer has two types of β phases. Since it has a mixed structure, the sliding properties of the surface layer are greatly improved. As a result, the surface layer exhibits excellent durability even at high speeds and under high surface pressure, and also has high strength.

Moreover, the surface layer formed by the local melting alloying treatment has strong adhesion to titanium or a titanium alloy as a base material, and does not peel off when sliding at high speed and under high surface pressure.

(3) Example Figure 1 shows a rocker arm 1 as a titanium alloy structural member.
The rocker arm 1 shown in FIG.
has.

When manufacturing rocker arm 1, Tt-6Af-4V
An α+β type titanium alloy material having the composition is used,
The surface layer 3 forming the slipper surface 2 is modified by subjecting the material to a local melting process using a high-density energy source.

The metal structure of the surface layer 3 consists of a first β phase containing a total solid solution type β stabilizing element and a second phase containing a eutectoid β stabilizing element.
It is composed of a mixture of two phases: the β phase and the β phase.

At least one of MO and V is applicable as the total solid solution β stabilizing element. The eutectoid β-stabilizing element is at least one selected from Fe, Cr, Mn, Co, and Ni.

The total solid solution type β stabilizing element forms a total solid solution with the α+β type titanium alloy that is the base material. 10% by weight of this element
By containing the above amount, the first β phase can be brought to room temperature. Furthermore, this element has the effect of improving the sliding properties and heat resistance of the first β phase.

In order to obtain these effects, the specific content of MO and (2) is 10% by weight or more in the case of Mo, and 14% in the case of V.
It is 9% by weight.

However, when the total solid solution β stabilizing element is added alone, the first
The hardness of the β phase is low, and sufficient wear resistance cannot be obtained.

In addition, by containing 3.5% by weight or more of the eutectoid β-stabilizing element, the second β phase is stabilized, and the hardness of the second β phase is increased by producing a precipitation hardening effect. can be improved.

The specific content of Fe, Cr, Mn, Co and Ni to obtain these effects is 3.5 to 15% by weight for Fe, 6.3% by weight or more for Cr, and 6.3% by weight or more for Mn. 6
．． The content is 4% by weight or more, 7% by weight or more for Co, and 9% by weight or more for Ni.

However, if the content of the eutectoid β-stabilizing element exceeds 40% by weight, segregation etc. will occur due to the low solid solubility of this element, making it difficult to obtain a stable second β phase. I won't be able to do it. Therefore, the upper limit of the content of this element is set at 40% by weight.

In addition, without adding any solid solution type β stabilizing elements, eutectoid type β
If only a stabilizing element is added, an intermetallic compound is formed due to the precipitation hardening effect, and the second β phase tends to become brittle. However, this problem can be solved by combining a completely solid solution β stabilizing element. It is resolved by this.

Dispersing hard particles in the surface layer 3 is an effective means for improving the wear resistance of the surface layer 3. In dispersing these hard particles, Mo and C powders containing solid solution β-stabilizing elements are used, and M
It is preferable to precipitate TIC as hard particles using the reaction of C→2Mo+C1Ti+C→T1C. This M
oC powder is MoI! ! : Also has the effect of facilitating alloying with Ti.

Hereinafter, the local melting alloying process of the rocker arm 1 will be explained.

Figure 2 shows the local melting alloying process using powder injection.
The rocker arm material 1° made of the base material (Ti-6AI!, -4V) is moved in the direction of the arrow, and its slipper surface corresponding portion 2° is irradiated with a carbon dioxide laser from the oscillator 5, and at the same time from the gas supply nozzle 6. Helium gas, which is a shielding gas, is supplied from the powder supply nozzle 7, and Moz C powder (total solid solution type β-stabilizing element) and Fe powder (eutectoid type β-stabilizing element) are respectively supplied.

The processing conditions are as follows.

Movement speed of rocker arm material 1° (processing speed): 30
0 Peng/closed carbon dioxide laser: output 5kW, spot diameter 2111,
Amplitude 5III, Power density 5~6X10'W/
cd Mo, C powder: diameter 10-44 μm, supply amount 15.7
g/win; FC powder: purity 99% or more,
Particle size: 200 mesh or less, supply amount: 4.6 g/m
By the above-mentioned treatment, a metal structure in which two phases, the first β phase and the second β phase are mixed, is obtained.

The average composition of the surface layer 3 obtained by the above treatment is T i
-27,1M o -7,9F e-3,3A l
-2.2V.

In local melting alloy processing using a high-density energy source such as a carbon dioxide laser, rapid solidification is achieved by self-cooling after melting, resulting in a fine and homogeneous metal structure, resulting in stable sliding properties and strength. . Furthermore, the adhesion of the surface layer 3 to the base material is strong.

In addition, as the local melting alloying treatment method, it is also possible to apply the bribrace method, in which powder is placed in advance at the slipper surface corresponding portion 2° of the cable material 1°.

Further, the present invention is also applied to structural members made of Ti alloy.

C1 Effect of the invention According to the invention, by specifying the modification treatment for obtaining the surface layer and the metal structure of the surface layer as described above,
It is possible to provide a titanium or titanium alloy structural member that has a surface layer that has high adhesion to the base material and has excellent sliding properties and strength.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cutaway front view of the main part of the rocker arm, and FIG. 2 is an explanatory diagram of the local melting alloying process. 1... Rocker arm (structural member), 3... Surface layer Fig. 1 Fig. 2

Claims (4)

[Claims] (1) A surface layer portion modified by local melting alloying treatment using a high-density energy source, and the metal structure of the surface layer portion is a first β phase containing a solid solution type β stabilizing element. and a second β phase containing a eutectoid β stabilizing element. (2) The total content of the solid solution β-stabilizing element is 10% by weight or more, and the content of the eutectoid β-stabilizing element is 3.5% by weight or more and 40% by weight or less. , the titanium or titanium alloy structural member according to item (1). (3) The total solid solution β-stabilizing element is at least one of Mo and V, and the eutectoid β-stabilizing element is at least one selected from Fe, Cr, Mn, Co, and Ni. The titanium or titanium alloy structural member according to item (1) or item (2). (4) the structural member is a rocker arm for an internal combustion engine;
The titanium or titanium alloy structural member according to item (1), item (2), or item (3), wherein the surface layer portion constitutes a slipper surface.