JP2626163B2 - Titanium alloy with excellent corrosion and wear resistance - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a titanium alloy having excellent corrosion resistance and wear resistance, and particularly having high resistance to wear (erosion corrosion) in a corrosive environment.

(Prior Art) Titanium alloys have high specific strength, and are excellent in corrosion resistance and heat resistance, and therefore, their applications are expanding as various mechanical component materials. However, since titanium alloys do not have sufficient wear resistance, they wear relatively easily in fluids containing solids, whether dry or wet.

Titanium exhibits a selected corrosion resistance in a wet environment. Although this property is maintained by a stable thin oxide film formed on the titanium surface, the oxide film is easily destroyed in an environment with wear. For this reason, titanium is usually slightly acidic (pH: 1 to 3) at which excellent corrosion resistance should be exhibited.
Environment), it has been difficult to use it for components of turbine blades and impellers, parts for chemical agitators and slurry processing equipment, and the like. Ni-based alloys such as Hastelloy C (trade name) have been used for such parts, but titanium alloys, which are lighter and have higher specific strength than Ni-based alloys, are It is much more advantageous as a material. That is, if abrasion resistance is imparted to a titanium alloy which is originally excellent in corrosion resistance, the titanium alloy is used even in an environment where erosion occurs, and the use thereof is further expanded.

As measures to improve the wear resistance of titanium alloys, a method of forming titanium nitride on the surface by heating or ion plating, or a method of melting the alloy surface by high-energy beam irradiation and adding a hard material such as TiN in the molten pool Or solid solution strengthening material (oxygen) is injected and mixed
No. 56561) A father has been proposed. However, it is difficult to provide practical wear resistance by any method. In the heating method, the product is deformed because the processing temperature is constant, and the ion plating method has a high processing cost,
In addition, there are many problems that there are restrictions on the product dimensions and that it is not easy to form a thick film of titanium nitride.

On the other hand, it is known to use a platinum group element in order to improve the corrosion resistance of titanium. For example, as JIS 11-13, there is titanium containing 012-0.25% of Pd.
JP-A-07041, JP-A-62-149836, JP-A-64-21040 and the like also propose a highly corrosion-resistant titanium alloy containing a platinum group element. However, these are all aimed at improving corrosion resistance, and have poor wear resistance and poor durability in an environment where corrosion and wear simultaneously progress.

The present inventors have searched for a new method for imparting wear resistance to titanium alloys, invented an alloy in which titanium carbide is dispersed in a β-phase titanium base material, and applied for a patent as Japanese Patent Application No. 63-282435. Was done. In the invention of the wear-resistant titanium alloy of the prior application, β-phase titanium has higher wear resistance than α-phase titanium and (α + β) -phase titanium, and titanium carbide (or harder ceramics and / or α-phase) is added thereto. It is based on the finding that the abrasion resistance is significantly improved by dispersing. The alloy of the prior application exhibits extremely selected durability in erosion by water jets and in dry wear environments.

(Problems to be Solved by the Invention) The present invention relates to the wear-resistant titanium alloy of the above-mentioned prior invention,
The object of the present invention is to provide a further improved resistance to erosion so that it can be used as a material for parts that are subject to wear in a highly corrosive environment.

(Means for Solving the Problems) The gist of the present invention is that one or more platinum group elements are used alone or in a total amount of 0.005 to 0.2.
A titanium alloy excellent in corrosion resistance and wear resistance, characterized in that titanium carbide is dispersed in a β-phase titanium base containing 5% by weight. Hereinafter, all the percentages related to the alloy components in the present specification represent "% by weight".

The above-mentioned alloy of the present invention may be the whole alloy material constituting various members, or a part of the member, for example, only the surface layer portion subjected to erosion corrosion may be the above-mentioned alloy.

Beta phase titanium base is not only platinum group element but also Ni and Co
One or two kinds may be contained alone or in a total amount of 0.1 to 5.0% by weight. It is indispensable to disperse carbon titanium in the β-phase titanium base, but an α-phase and / or a hard ceramic may be further dispersed. Hard ceramics are, for example, particles of W ₂ C, NiC, and TiN, preferably having a particle size of 150 μm or less.

(Function) The base material of the alloy of the present invention is β-phase titanium. β-phase titanium means β-phase stabilizing elements Cr, Mo, Ni, Ta, V, Fe, Mn
It is a substrate that contains titanium β in a body-centered cubic structure at room temperature. As an alloy of β-phase titanium, Ti
-2Al-8V-6Cr-4zr-4Mo, Ti-15V-3Al-3Sn-3Cr,
Ti-10V-2FeP3Al and the like. Of the above-mentioned β-stabilizing elements, eutectoid β-stabilizing elements such as W and Cr are particularly advantageous.
Therefore, Ti-6Al-4V which is an (α + β) titanium alloy
By adding, for example, 25% W or 10% Cr, an alloy of β-phase titanium base can be obtained. In addition, even if a large amount of W and Cr is contained in pure α-based titanium, a β-phase titanium base can be obtained.

In the above β-phase titanium base, one or more platinum group elements are contained.
0.005 ~ 0.25% must be had. Practical ones of the platinum group elements are Pd and Ru, but Os, Ir, P
t and Rh can also be used. These elements have the effect of improving the corrosion resistance of titanium alloys, but their effects are not apparent unless the content of single or combined ignition is at least 0.005%. The greater the content, the better the coping performance, but if it exceeds 0.25%, the effect tends to be saturated. Also, since these are extremely effective elements, the upper limit should be practically limited to 0.25%. is there.

The base can contain Ni and / or Co. When one or more of these elements are contained in 0.1% or more in total, they have an effect of improving the corrosion resistance by reducing the hydrogen overvoltage of the alloy similarly to the platinum group elements. This effect appears more remarkably in the presence of the platinum group element. However, if the content exceeds 5.0%, the deterioration of the alloy workability increases, so the upper limit of the content is preferably 5.0%.

The titanium carbide particles must be distributed as uniformly as possible on the above-mentioned base material. In this case, the dispersed titanium carbide is composed of TiC crystallized during solidification and TiC precipitated in the solid phase.
It is. As a method for dispersing such TiC,
In the current amphoteric statement that becomes β-phase titanium alloy as described above, 0.
2. Method of containing and melting 5.0% carbon (this carbon may be ignited in the form of carbide), solidifying and dispersing titanium carbide, using a graphite crucible as a raw material to become β-phase titanium alloy A method of producing TiC by supplying C from a crucible and dissolving and decomposing into a titanium alloy powder to form a β phase and adding a powder of a carbide (eg, W ₂ C, Cr ₃ C ₂ ) powder to titanium. There is a method of spraying on the alloy surface. In the method of the above, if the C content in the raw material is not 0.2% or more,
Are dissolved in β-phase titanium and do not disperse as carbides. On the other hand, if the content of C exceeds 5.0%, cracks occur during solidification of the alloy, and hot workability and toughness deteriorate. In addition, as a means for containing C in the alloy, if a carbide having less stability as a substance than TiC, such as W ₂ C and Cr ₃ C ₂ NbC, is added in a finely dissolving manner, these carbides are decomposed. Thus, TiC is generated, and at the same time, W, Cr, Nb, etc. separated as an alloy component of the base material have the effect of reducing the β phase.

FIG. 1 is a diagram schematically showing the microstructure of the Ti alloy of the present invention. (A) is obtained by separating only titanium carbide (TiC) into a β-phase titanium base, (b) is obtained by dispersing α phase in addition to TiC, (c) is obtained by dispersing TiC and hard ceramics, and (D) is one in which TiC, α phase and hard ceramics are dispersed.

The alloy of (a) can be manufactured by the above-mentioned manufacturing method,
In this case, the crystallized titanium carbide has an elliptical shape, a spherical shape, and a shape in which these are connected in a network. The size is 0.5 to maintain the uniformity of the element and the uniformity of the body wear.
Fine particles having a size of about 25 μm are desirable. If the dispersion amount of titanium carbide is too large, the ductility of the alloy is impaired, so it is preferable to keep the dispersion amount to 30% by volume or less.

To disperse the α phase as in (b) and (d),
An alloy in which titanium carbide is dispersed in a β-titanium base as in (a) may be aged at 350 to 550 ° C. By this treatment, a fine α phase of about 0.05 to 0.1 μm is precipitated and age hardened, and the wear resistance of the alloy is further improved. If the temperature of the aging treatment is lower than 350 ° C., the treatment takes a long time, and the age hardening is not sufficient. If the temperature exceeds 550 ° C., overaging may occur and the hardness may decrease. The dispersion amount of the α phase is
It is good to be 20 volume% or less.

Alloys in which hard ceramics are dispersed as in (c) and (d) require β-phase titanium containing 0.2 to 5.0% of C as described above, into which hard ceramic powder is charged and stirred. Obtained by coagulation. in this case,
Only the surface layer of the member is melted, and ceramic powder is added thereto, so that only the required surface layer has the structure of (c) or (d). The hard ceramic, said W ₂ C, NiC, other _{TiN, WC, Cr 3 C 2} , NbO, SiC, TiN, A
Fine powder of 150 μm or less such as l ₂ O ₃ is preferred. 150 μm
The coarser the particles, the more likely the ceramic particles are peeled off and dropped off from the surface during use of the alloy, and the hardening of the wear resistance is reduced. The dispersion amount of the hard ceramics should also be up to 20% by volume, because when it is changed, the ductility of the alloy is impaired.

The alloy (d) is manufactured by manufacturing an alloy in which hard ceramics are dispersed as described above, and then precipitating a fine α phase by aging at 350 to 550 ° C.

The alloy of the present invention has extremely excellent corrosion resistance by containing a platinum group element, or furthermore, Ni and Co, and at the same time, titanium carbide having a hardness of 100 Hv or more in the β phase matrix,
Or, since the hard ceramics and fine α phase particles are further dispersed, the abrasion resistance is high. Therefore, sufficient durability is exhibited even in a use environment in which corrosion and wear progress simultaneously.

The alloy of the present invention can maintain the specific gravity at 5 or less by adjusting the contained components, and can maintain the inherent properties of the titanium alloy, which is high in specific strength when measured. Further, since hot working can be easily performed by heating at about 1000 ° C., it is easy to mold into various parts.

When only a predetermined part of the part is made of the alloy of the present invention,
As described above, the alloy of the present invention may be formed on the surface layer of the component by means such as thermal spraying. Further, the alloy of the present invention can be used by being joined to the surface of another titanium alloy part by TIG welding.

(Example) An alloy having the composition shown in Table 1 was melted by button melting, and was
An ingot of 50 × 100 (mm) was obtained. The raw materials used are
Sponge titanium, sponge zirconium, electrolytic tin, Al-
V master alloy, Al-Mo master alloy, pure Al, and Pd, Ru, Ni, Co
And powders of W ₂ C, Cr ₃ C ₂ , NbC, and TiN (particle size: 80 to 150 μm).

The above ingot was heated to 1050 ° C., and then hot-rolled in three passes to form a plate having a pressure of 10 mm. At this time, the occurrence of defects such as cracks was investigated.

Alloy Nos. 13 to 18 shown as comparative examples in Table 1 do not contain a platinum group element, and Nos. 19 and 20 shown as conventional examples are existing β-type titanium. Among the alloys of the present invention, No. 6,
Nos. 7, 8, 11, and 12 and Nos. 16 to 18 of the comparative examples are after hot working.
The α phase is precipitated by performing aging treatment at 450 to 500 ° C for 4 to 20 hours.

The hardness (Hv) at room temperature of the sample thus obtained was measured, and a 10 × 10 sliding wear test piece having a diameter of 10 mm and a length of 40 mm was obtained.
× 15 (mm) erosion test specimen and 10 × 20 × 20
(Mm) hydrochloric acid corrosion test pieces were collected and subjected to each test.

Further, a test piece for X-ray analysis was also collected, and the phase was fixed with a diffractometer.

The abrasion test was performed by a pin-on-disk method shown in FIG. The test conditions are as follows.

Pressing load of test piece: 2 kg Sliding speed between test piece and mating material (disk): 62.8 m / min Sliding distance: 2.5 × 10 ⁴ m Mating material (disk): 60 kgf / mm Class ² high-tensile steel Friction surface Lubrication: None The wear resistance was evaluated based on the weight loss of the test piece.

The erosion test was performed by the jet method shown in FIG. The test piece was mirror-finished by buffing and tested under the following conditions.

Water jet nozzle diameter: 1.2mm Spray water flow rate: 370mMsec Nozzle-specimen distance: 65mm Spray angle: 90 ° C Spray time: 600sec .

In the hydrochloric acid corrosion test, the steel sheet was immersed in a 5% by weight HCl boiling solution for 20 hours, the corrosion loss was measured, and the corrosion resistance was evaluated in terms of mm / year.

 The test results are summarized in Table 2.

As is clear from Table 2, the alloy of the present invention is excellent in all of the sliding wear resistance, erosion resistance and hydrochloric acid corrosion resistance. Although the alloy of the comparative example contains titanium carbide (or further α phase, TiN), it can be selected for sliding wear resistance and erosion resistance, but is inferior in hydrochloric acid corrosion resistance. Therefore, it cannot be used in an environment where erosion corrosion occurs. Conventional practical alloys are far inferior in all properties to the alloys of the present invention. In addition, the alloy of the present invention is equivalent to a conventional titanium alloy also in hot workability.

Table 3 shows some of the test results that were angry at examining the proper contents of platinum group elements and Ni and Co.

The base is the same 6Al-4V alloy as No. 2 in Table 1, and Ru, P
Test pieces were prepared under the same conditions as in No. 2 except that the contents of d, Ni and Co were changed.

From Table 3, it is clear that those with too small contents of Ru, Pd, Ni and Co have poor corrosion resistance (hydrochloric acid corrosion resistance). On the other hand, those to which a large amount of Ru and Pd are added have excellent corrosion resistance, but it can be seen from the comparison of No. 2 in Table 2 that the improvement in corrosion resistance is saturated. That is, excessive addition of the platinum group element is not preferable because it increases the material price. Alloys containing excessive amounts of Co and Ni have poor hot workability, and their addition needs to be kept within an appropriate range.

(Effect of the Invention) As shown in the examples, the titanium alloy of the present invention has excellent corrosion resistance and extremely good wear resistance. Therefore, the alloy of the present invention can be used in a dry environment,
It can be used satisfactorily even in a condition that involves abrasion in a wet corrosive environment. The alloy can be used not only for the above-mentioned turbine blades, impellers and valve members of chemical devices, but also for valve trains of automobiles or artificial bones (joints).

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing the microstructure of the alloy of the present invention. FIG. 2 is a diagram illustrating a test method of a sliding wear test. FIG. 3 is a diagram illustrating a test method of an erosion test.

Claims (5)

(57) [Claims] (1) one or more of platinum group elements alone or in total
Tatin alloy excellent in corrosion resistance and wear resistance, characterized in that titanium carbide is dispersed in a β-phase titanium base containing 0.005 to 0.25% by weight. 2. The method according to claim 1, wherein the β-phase titanium base further comprises a platinum group element.
Ni and Co 1 or 2 types alone or in total 0.1 to 5.0
The titanium alloy according to claim 1, which is contained by weight%. 3. The titanium alloy according to claim 1, wherein the α phase is further dispersed in the β phase titanium base in addition to the titanium carbide. 4. The titanium alloy according to claim 1, wherein a hard ceramic is further dispersed in the β-phase titanium base in addition to the titanium carbide. 5. The titanium alloy according to claim 1, wherein the α phase and the hard ceramic are further dispersed in the β phase titanium base in addition to the titanium carbide.