JPH062189A - Plating bath for titanium-containing metallic material and plating method - Google Patents

Abstract

PURPOSE:To obtain a plating bath for titanium-containing metallic material capable of forming an excellent wear resistant plating film without generating deterioration of fatigue strength by preparing the plating bath containing Ni<+2> ion, Co<2+> ion and MoO4<2+> ion of a specific conc. and having a specific pH. CONSTITUTION:The plating bath containing 30-120g/l at least one kind of Ni<2+> ion and Co<2+> ion and 2-25g/l MoO4<2+> ion and having pH 3.5-7.0 is prepared. The plating layer is formed without deteriorating fatigue strength by electrolytic plating the titanium-containing metallic material by the use of the plating bath. Nickel sulfaminate or the like as a compound for supplying Ni<2+> ion, cobalt sulfaminate or the like as a compound for supplying Co<2+> ion and ammonium molybdate or the like as a compound for supplying MoO4<2+> ion are used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroplating bath for titanium-containing metal materials and a plating method. More specifically, the present invention relates to an electroplating bath useful for forming a plating layer having excellent wear resistance and fatigue strength on the surface of a titanium-containing metallic material, and an electroplating method.

In the present specification, the titanium-containing metallic material includes metallic titanium material and titanium alloy material.

[0003]

2. Description of the Related Art It is known that various metal plating films are formed on a titanium-containing metal material by a wet plating method. However, the metal plating film formed by the conventional technique has a defect that the metal plating film is easily peeled off because of poor adhesion to the surface of the titanium-containing metal material.

Further, the plated product obtained by forming the hard metal plating film on the surface of the titanium-containing metal material by the conventional method has a problem that its fatigue strength is low.
In particular, when the surface of a titanium-containing metal material was plated with a hard metal of nickel and / or cobalt by a conventional technique, the fatigue strength of the plated product obtained was unsatisfactory in practice.

[0005]

DISCLOSURE OF THE INVENTION According to the present invention, when a hard plating film containing at least one selected from nickel and cobalt is formed on the surface of a titanium-containing metal material, the resulting plated product has a reduced fatigue strength. It is intended to provide an electroplating bath for a titanium-containing metal material and an electroplating method which do not cause the above phenomenon.

[0006]

The present inventors have proposed an electroplating bath for a titanium-containing metal material containing at least one selected from nickel ions (Ni ²⁺ ) and cobalt ions (Co ²⁺ ), Specific amount of molybdate ion (MoO
_{By including 4} ^2- ), we succeeded in solving the above problems.

That is, the plating bath for a metal material containing titanium according to the present invention contains 30 to 120 g / liter of at least one selected from Ni ²⁺ ions and Co ²⁺ ions and 2 to 25 g / liter of MoO _4. It is characterized by containing ^2- ions and having a pH of 3.5 to 5.0.

The method for electroplating a titanium-containing metal material according to the present invention comprises 30 to 120 g / liter of at least one selected from Ni ²⁺ ions and Co ²⁺ ions, and
The present invention is characterized in that a titanium-containing metal material is electroplated in a plating bath containing 25 g / liter of MoO ₄ ²⁻ ions and having a pH of 3.5 to 7.0.

Further, in the method of the present invention, the plating bath may contain hard fine particles, and a composite plating film containing the hard fine particles may be formed.

[0010]

In the present invention, the titanium-containing metallic material is a metallic titanium material or a titanium alloy material such as 6Al-4.
V-Ti alloy material and Ti-3Al-8V-6Cr-
4Mo-4Zr alloy materials (commonly known as BETAC) are included, and these materials are used for applications such as sliding members for internal combustion engines, such as camshafts, connecting rods, engine valves, and valve springs.

The electroplating bath of the present invention contains 30 to 120 g.
/ Liter, preferably 50-100 g / liter N
at least one selected from i ²⁺ ions and Co ²⁺ ions, which comprises a MoO ₄ ^2-ions 2～25G / liter, using such electroplating baths, titanium-containing metallic material When electroplating is carried out, a hard metal film of Ni-Mo, Co-Mo or Ni-Co-Mo alloy can be formed on the surface of this material, and the obtained plated product shows excellent fatigue strength.

Each component contained in the electroplating bath of the present invention will be described. 1) Ni ²⁺ ions and Co ²⁺ ions These metal ions electroplate on the surface of the titanium-containing metal material by electroplating, at which time hydrogen is generated in the plating bath. Although present as molybdenum or melibudate ion in the plating bath, the molybdate ion is reduced to metallic molybdenum by the hydrogen, and an alloy plating film is formed by the metallic molybdenum and nickel and / or cobalt. To be done.

The concentration of Ni ²⁺ ions and / or Co ²⁺ ions is 30 to 120 g / liter. When this concentration is less than 30 g / liter, and 120 g
If it is higher than 1 liter / liter, the balance of the electrodeposition amount of nickel and / or cobalt and molybdenum becomes poor, and the strength of the obtained alloy plating film becomes insufficient.

In the electroplating bath of the present invention, as the compound supplying Ni ²⁺ ions, for example, nickel sulfamate, nickel sulfate, nickel chloride and the like can be used.

As the compound for supplying Co ²⁺ ions, for example, cobalt sulfamate, cobalt sulfate, etc. can be used.

2) MoO ₄ ²⁻ ion As described above, the molybdate ion is reduced to molybdenum metal by hydrogen generated during the electrodeposition of Ni and / or Co ion, and the alloy plating film together with Ni and / or Co is formed. To form.

In the electroplating bath of the present invention, MoO ₄
^{The 2-} ion concentration needs to be ^{2 to} 25 g / liter. If this concentration is less than 2 g / liter,
If the effect of preventing reduction of fatigue strength in the obtained plated product is insufficient, and if it is higher than 25 g / liter, the strength of the obtained alloy plating film is insufficient.

Examples of compounds that supply MoO ₄ ²⁻ ions to the electroplating bath include ammonium molybdate,
And sodium molybdate and the like can be used.

In the electroplating bath of the present invention, 20 to 60 g /
It is preferable to add 1 liter of alkali metal borate such as sodium borate and potassium borate. The alkali metal borate salt is effective as a buffer for adjusting the pH of the plating bath.

The concentration of alkali metal borate is 20 g /
If it is less than 1 liter, the pH adjusting effect may be insufficient, and if it is more than 60 g / liter, the pH adjusting effect is saturated and the result is not improved.

It is preferable to add at least one selected from 3 to 7 g / liter of saccharin and saccharinates such as sodium saccharinate and potassium saccharinate to the electroplating bath of the present invention.
Such a saccharin compound has an effect of improving the smoothness of the plating film formed on the surface of the titanium-containing metal material. If the concentration of the saccharin compound is less than 3 g / liter, the smoothness improving effect may be insufficient, and if it is more than 7 g / liter, the smoothness improving effect may be saturated. , The film adhesion may be adversely affected.

The electroplating bath of the present invention has a pH of 3.5 to 7.
It is adjusted to 0, preferably 3.5 to 5.0. When the pH is less than 3.5, the plating pretreatment film is dissolved during the plating treatment, resulting in the inconvenience that good adhesion cannot be obtained. When it is higher than 7.0, molybdate, nickel Compounds and the like are deposited as solids from the plating bath, which causes a disadvantage that a normal plating film cannot be obtained.

In the electroplating method of the present invention, the titanium-containing metal material used in the electroplating step is prepared by a conventional method.
The surface is cleaned, and if necessary, copper strike plating is applied. The pre-treated titanium-containing metal material is electroplated by the method of the present invention in an electroplating bath having a predetermined composition. This electroplating step is performed by passing a direct current having a current density of preferably 0.1 to 10 A / dm in an electroplating bath at 40 to 60 ° C. Generally, the thickness of the obtained alloy plating film is preferably 5 to 50 μm, and the weight thereof is preferably 45 to 450 g / m ² .

In the electroplating bath used in the method of the present invention, in addition to the above-mentioned components, other components such as hard fine particles (for example, SiC, Si ₃ N ₄ , Al ₂ O ₃ , WC, Zr) are used.
Fine particles such as fine ceramics selected from B ₂ , diamond, CrB, etc., having a particle size of 0.1 to 10 μm) may be included. In this case, a composite plating film containing hard particles can be obtained. The hard fine particles are preferably contained in the electroplating bath at a concentration of 30 to 300 g / liter.

The plating treatment of the titanium-containing metallic material using the method of the present invention is generally performed by the following steps. 1 Degreasing 2 Washing with water 3 Pickling with water 4 Washing with water 5 Copper strike plating 6 Washing with water 7 Plating according to the method of the present invention 8 Washing with water 9 Vacuum heat treatment In the above vacuum heat treatment, generally at a temperature of at least 450 ° C. under a vacuum of 10 ⁻¹ to 10 ⁻⁵ Torr. It is preferred that heating is applied for at least 1 hour.

[0026]

The present invention will be further described by the following examples.

Example 1 A titanium-containing metal material was plated with a Ni-Mo alloy by the following steps. (1) Test material: 6A14VTi material The shape and dimensions are the same as those of No. 1-6 test pieces specified in JIS-Z-2274, Metal Rotating Bending Fatigue Test Method.

(2) Surface treatment (a) Surface cleaning: Alkaline degreasing (manufactured by Nippon Parkerizing Co., Ltd., alkaline cleaner CL-391, immersed in 50 g / l aqueous solution for 2 minutes) (b) Washing with water (c) Pickling with 50% HCl Aqueous solution 50 ° C. for 10 minutes (d) Washing with water (e) Copper strike plating bath composition Copper cyanide (CuCN) 60 g / liter Sodium cyanide (NaCN) 70 g / liter Potassium sodium tartrate 50 g / liter (KNaC ₄ H ₄ O ₆ ) solution Temperature 40 ° C Current density 5A / dm ² Coating thickness 2μm (f) Washing with water

(G) Nickel-molybdenum alloy plating bath composition Ni ²⁺ ion 90 g / liter (nickel sulfamate) MoO ₄ ^2- ion 5 g / liter (sodium molybdate) pH 4.0 Liquid temperature 60 ° C. Current density 2 A / dm ² Film thickness 20 μm (h) Washing with water (i) Vacuum heat treatment Pressure 10 ^-2 Torr Temperature 450 ° C Heating time 1 hour (j) Allowing to cool

(3) Fatigue Strength Test The obtained plated products were subjected to a fatigue strength test according to JIS-Z-2274 "Method of rolling fatigue test for metallic materials". However, the temperature of the test atmosphere was 30 ° C. The test results are shown in FIG.

Example 2 A titanium-containing metal material was plated with a cobalt-molybdenum alloy as follows. (1) Test material: same as in Example 1

(2) Surface treatment The same procedure as in Example 1 was carried out except that the step (g) was performed under the following conditions. (G) Cobalt-molybdenum alloy plating bath composition Co ²⁺ ion 90 g / liter (cobalt sulfamate) MoO ₄ ^2- ion 5 g / liter (sodium molybdate) sodium borate 40 g / liter pH 5.5 (however, ammonium salt Liquid temperature 60 ° C Current density 5A / dm ² Coating thickness 20μm

(3) Fatigue strength test: The same test results as in Example 1 are shown in FIG.

EXAMPLE 3 Nickel-cobalt-
Molybdenum alloy plating was applied. (1) Test material: same as in Example 1

(2) Surface treatment The same procedure as in Example 1 was carried out except that the step (g) was performed under the following conditions. (G) Nickel-cobalt-molybdenum alloy plating bath composition Ni ²⁺ ion 55 g / liter (nickel sulfamate) Co ²⁺ ion 45 g / liter (cobalt sulfamate) MoO ₄ ^2- ion 5 g / liter (sodium molybdate) boric acid Sodium 40 g / liter Saccharin soda 5 g / liter pH 3.5 Liquid temperature 60 ° C. Current density 0.5 A / dm ² Film thickness 20 μm

(3) Fatigue strength test: The same test results as in Example 1 are shown in FIG.

Comparative Example 1 A titanium-containing metallic material was nickel-plated as follows. (1) Test material: same as in Example 1

(2) Surface treatment of test piece The same procedure as in Example 1 was carried out except that the step (g) was performed under the following conditions. (G) Nickel plating bath composition Nickel sulfamate 480 g / liter Sodium borate 40 g / liter Saccharin soda 5 g / liter pH 4.2 Liquid temperature 60 ° C. Current density 10 A / dm ² Coating thickness 20 μm

(3) Fatigue strength test: The same test results as in Example 1 are shown in FIG.

Comparative Example 2 A titanium-containing metal material was plated with cobalt as follows. (1) Test material: same as in Example 1

(2) Surface treatment The same procedure as in Example 1 was carried out except that the step (g) was performed under the following conditions. (G) Cobalt plating bath composition Cobalt sulfamate 450 g / liter Sodium borate 40 g / liter Saccharin soda 5 g / liter pH 4.5 Liquid temperature 60 ° C. Current density 10 A / dm ² Coating thickness 20 μm

(3) Fatigue strength test: The same test results as in Example 1 are shown in FIG.

As is clearly shown in FIG. 1, the plating film formed on the titanium-containing metal material according to the present invention does not reduce the fatigue strength of the obtained plated product, or is extremely small. Therefore, in comparison with the nickel-plated and cobalt-plated products obtained in Comparative Examples 1 and 2 showing a remarkable decrease in fatigue strength, the excellent effect of molybdenum addition was confirmed.

[0044]

INDUSTRIAL APPLICABILITY The electroplating bath and the electroplating method of the present invention provide an excellent wear-resistant plating film on a titanium-containing metal material without reducing the fatigue strength of the plated product or by a very slight decrease. And has an excellent value in practical use.

[Brief description of drawings]

FIG. 1 is a graph showing the fatigue strength of plated products prepared in Examples 1 to 3 and Comparative Examples 1 and 2.

Claims (3)

[Claims] 1. At least one selected from Ni ²⁺ ions and Co ²⁺ ions at 30 to 120 g / liter and MoO ₄ ²⁻ ions at ^{2 to} 25 g / liter, and 3.5 to A plating bath for a metal material containing titanium, which has a pH of 7.0. Of 2. A 30 to 120 g / liter, at least one selected from Ni ²⁺ ions and Co ²⁺ ions, contain and MoO ₄ ^2-ions 2～25G / liter, and 3. A method for electroplating a titanium-containing metal material, which comprises electroplating the titanium-containing metal material in a plating bath having a pH of 5 to 7.0. 3. The electroplating method according to claim 2, wherein the plating bath further contains hard fine particles to form a composite plating film containing the hard fine particles.