JP2777468B2 - Composite material for mechanical structure with excellent rolling fatigue life - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a composite material for a machine structure which has excellent rolling fatigue life and is used for wear parts of various machines and transporting machines.

(Prior art) Conventionally, carbon steel, nickel chromium molybdenum steel, chromium molybdenum steel, etc. are subjected to carburizing, quenching and tempering, nitriding or nitrocarburizing to wear parts of various molds and machines. Steel materials are widely used and exhibit good wear resistance. However, these steel materials have a large specific gravity, and it is difficult to cope with the movement to reduce the weight.

Titanium and titanium alloys, and aluminum and aluminum alloys have begun to attract attention as materials that can cope with the movement of weight reduction. BACKGROUND ART Titanium and titanium alloys, and aluminum and aluminum alloys have been widely used as various members of various chemical industry and aeronautical and space transportation vehicles because of their excellent corrosion resistance and large high-temperature specific strength.

2. Description of the Related Art In recent years, as the demands for upgrading various types of transports, such as automobiles, have increased, it has become necessary to mount various functional components in order to satisfy functional improvements such as comfortable driving and safe driving. As a result, the problem of increasing the body weight has arisen.

On the other hand, there is still a strong demand for a reduction in fuel consumption, and in order to solve these problems at the same time, the use of titanium and titanium alloys and aluminum and aluminum alloys instead of conventional steel materials has begun to be studied.

However, titanium and titanium alloys and aluminum and aluminum alloys are known to be extremely inferior in seizure resistance and wear resistance as they are, so far, as a sliding member or shaft material of a machine, Surface treatments such as electroplating, electroless plating, vapor phase plating, gas nitriding, and thermal spraying have been attempted.

Among these, if a plating technique such as electroplating or electroless plating can be adopted, the member can be provided most simply and at low cost.

(Problems to be Solved by the Invention) However, in electroplating and electroless plating using an aqueous solution, titanium and titanium alloys and aluminum and aluminum alloys form a strong oxide film on the surface, so that good adhesion of the plating layer is achieved. Can not be obtained.

In the case of vapor-phase plating and gas nitriding, usually 5 μm is used.
m, and cannot withstand sliding wear and rolling wear under a high surface pressure.

Further, since the sprayed coating has a high surface pressure in rolling wear, it is difficult to obtain a coating having sufficient strength to withstand this. For example, titanium and titanium alloys and aluminum and aluminum alloys are used in any of the surface treatment methods. Cannot provide sufficient abrasion resistance.

For example, taking a shaft as shown in FIG. 4 as an example, at the contact portion between the ball bearing and the roll bearing of the shaft,
Rolling wear characteristics as well as sliding wear are required instead of total wear resistance. Maximum i.e., the point contact portion of the shaft member, in particular is耐転dynamic wear resistance requirements, with the number 100 kgf / mm ² things maximum contact stress = high surface pressure is applied, at several tens to several hundreds of 100μm from the surface of the material The most characteristic feature of this kind of rolling wear is that a shear stress is generated and the stress is repeatedly applied, so that a fatigue crack is generated in the material and leads to flaking. Therefore, for such applications, ceramic hard materials such as WC and TiN, which are generally well-known and generally used as high wear-resistant materials, are excellent in sliding wear resistance but poor in toughness, and in rolling wear resistance. Inferior.

Therefore, the present inventors propose a light and wear-resistant composite material using titanium and a titanium alloy, aluminum and an aluminum alloy as a base material in order to cope with the trend of weight reduction.

(Means for Solving the Problems) In view of the problem of wear resistance of titanium and titanium alloy and aluminum and aluminum alloy subjected to the surface treatment described above, the present inventors have conducted intensive studies. , Which was completed as a result of repeated studies.
The surface of titanium or titanium alloy and aluminum or aluminum alloy whose surface is 0.5μm or more and whose PPI ₅₀ is roughened to 130 or more
At least two Ni-P plating layers, an inner layer having a crystal plane orientation of <111> as a main component with a content of 4% by weight or more and an outer layer having a P content of less than 4% by weight and a plating hardness of HV500 or more, It is a coated composite material for machine structure with excellent rolling fatigue life.

The second invention is a composite material for a mechanical structure excellent in rolling fatigue life according to claim (1), wherein the concentration of P in the Ni—P plating layer changes continuously between the inner layer and the outer layer.

The third invention is directed to a crystal orientation <111 of Ni-P plating of the outer layer.
<1> is a composite material for mechanical structure excellent in rolling fatigue life according to claim (1), wherein the integrated strength of the formula (1) satisfies the following expression.

[<111> / (<111> + <200> + <220> + <311> + <222>)) × 100 ≦ 90 …… In the fourth invention, the surface of titanium or a titanium alloy and aluminum or an aluminum alloy The composite material for mechanical structure excellent in rolling fatigue life according to claim (1), which has been subjected to a surface roughening treatment with a solution containing hydrofluoric acid.

(Function) A strong anchor effect is required to firmly adhere the hard plating layer to the surface of titanium or a titanium alloy and aluminum or an aluminum alloy. However, the surface state is Ra 0.5 μm by etching or shot blasting. Above, and by adjusting the PPI to ₅₀ or more, a strong anchor effect can be obtained. Here, PPI (Peaks Per I
nch) sets a constant reference level H in both positive and negative directions from the average line of the extraction curve (measurement value) of the contact type surface roughness meter, and after exceeding the negative reference level and exceeding the positive reference level, 1
The number of peaks is calculated and the number of peaks per inch is displayed. That is, the PPI ₅₀ 130 has a reference level of ₅₀ μinch and 1
Shows 130 peaks per inch. This makes it possible to suppress peeling of the hard plating layer from the interface between titanium or a titanium alloy and aluminum or an aluminum alloy.

Further, in order to improve the plating adhesion to titanium or a titanium alloy and aluminum or an aluminum alloy, the surface roughness of the material to be plated is kept as consistent as possible with the crystallographic plane orientation of the plating. Due to the synergistic effect with the adjusting effect, a higher plating adhesion can be obtained.

Specifically, the densest plane orientation of titanium <0001>
It is extremely effective to set the crystal plane direction of the Ni-P plating of the inner layer to the <111> orientation in order to make the crystal plane coincide. For this purpose, the P content of the Ni-P plating layer is set to 4% by weight or more,
The thickness of the plating layer needs to be 1.0 μm or more.

The intermediate layer or the outer layer plated on the upper surface of the inner layer must have a P content of less than 4% by weight in the Ni-P plated layer in order to satisfy both hardness and toughness. Also, by gradually decreasing the P content from the inner layer to the outer layer, a plating layer having both toughness and hardness and excellent in rolling contact fatigue life can be obtained. That is, unlike the inner layer, the outer layer is not so important in the adhesion to the material to be plated, but rather the toughness and hardness are important. Therefore, the P content of the outer layer is set to less than 4% by weight, and the integrated intensity of the crystal plane orientation <111> of Ni-P plating is limited to 90% or less. The integral intensity is [<111> / (<111> + <200> + <220> + <31
1> + <222>)] × 100%.

As the type of hard plating, electroless Ni-P plating, hard Cr plating, electrolytic Ni-P plating and the like can be considered, but electrolytic Ni-P plating is considered to be the most advantageous in terms of plating speed and cost.

Features of the rolling wear was as high surface pressure described above, contact stress is several 100 kgf / mm ^2, the maximum shear stress, the number 10 from the contact surface
It occurs at a depth of several 100 μm. Further, the shaft and the bearing are subjected to repeated rolling stress, so that the track is separated and cannot be rolled. This phenomenon is called flaking and is a kind of fatigue failure of the shaft and bearing material, which determines the life of the shaft and bearing.

Therefore, the inventors conducted a rolling wear test for selecting a coating material. The results are described below.

FIG. 1 is a schematic view of a rolling wear test method, in which 1 denotes a test piece, 2 denotes an evaluation surface, 3 denotes a ball bearing, 4 denotes a bearing race, and 5 denotes a rotating shaft. An evaluation surface 2 is provided at the tip of the test piece 1, and the evaluation surface 2 is a ball bearing 3.
It is tapered so as to contact with. The required number of ball bearings 3 are arranged in a bearing race 4.
The bearing race 4 is mounted on the rotating shaft 5 and rotates together with the rotating shaft 5. The rotating shaft 5 is connected to a rotating device (not shown). The test is performed by applying a load P to the test piece 1 and rotating the rotating shaft 5.

There are three kinds of test materials: Ti-6Al-4V as a base material, a base material sprayed with WC, a base material subjected to electrolytic Ni-P plating, and a base material as it is. These were subjected to a finish rolling wear test in the shape of the test piece 1. The test results are shown in FIG. 2 and FIG.

FIG. 2 summarizes the rolling fatigue life of the test material, and FIG. 3 summarizes the relationship between the electrolytic Ni-P plating thickness and the rolling fatigue life.

As shown in FIG. 2, the life of each test material is about 5 hours when sprayed with WC. This is probably because the WC film shows good wear resistance in sliding wear, but in rolling wear, the WC film was broken and dropped due to high surface pressure. Of course, Ti-6Al-4V as a base material has a life of 5 hours or less.

FIG. 3 shows the relationship between the electrolytic Ni-P plating thickness and the rolling fatigue life in the rolling wear test. It is clear that the rolling fatigue life of electrolytic Ni-P plating increases sharply with increasing plating thickness.

From this result, the thickness of the coating material to improve the rolling fatigue life of electrolytic Ni-P plating was determined by stopping the location where the maximum shear stress was generated inside the coating material and the rolling fatigue resistance of the coating material. The thickness is preferably 100 μm or more in order to make it possible and effective, and from the viewpoint of imparting abrasion resistance, it is sufficient to use 100 μm. Further, increasing the thickness of the coating material is not preferable from the viewpoint of reducing the weight as the object of the present invention.

The hardness of the coating material is adjusted to the required hardness depending on the plating conditions.However, considering the rolling fatigue life, it is important to consider not only hardness but also toughness, and that these are balanced. It is important. Therefore, the hardness of the coating material is limited to HV500 or more in consideration of toughness.

The manufacturing process of the composite material for a machine structure of the present invention is roughly as follows. Machining of base metal (titanium or titanium alloy and aluminum or aluminum alloy) Alkaline degreasing (sodium orthosilicate 5% solution, 70 ° C) Rinsing Etching (fluoric acid) Rinsing Activation treatment Rinsing Electroplating or electroless plating is there.

In the conventional method, etching is naturally performed as a pretreatment for plating. However, the acid used for this etching is mainly nitric acid, hydrofluoric acid or nitric hydrofluoric acid obtained by mixing them, and these conventionally used mineral acids cannot form the rough surface specified in the present invention. The surface is simply etched or even smoothed out.

According to the findings of the inventors, in order to obtain the rough surface defined in the present invention by chemical etching, a hydrofluoric acid salt such as NH ₄ FHF or NaFHF is necessary, and it is generally used as another etching agent. Nitric acid and hydrofluoric acid are effective as brighteners,
It is not a preferred agent for roughening as defined in the present invention.

Further, in the present invention, after etching for roughening as necessary, before hard plating, phosphoric acid electrolytic treatment for removing surface smut and chromic acid for putting out a metal surface,
Activation treatment with an acid such as hydrofluoric acid can be performed. That is, the steps up to plating after once forming the rough surface on the material surface are the same as the usual method. This is the same for the pretreatment of the roughening etching.

In addition, regarding the necessity of heat treatment after plating, in the prior art, in order to improve the adhesion of the plating to the titanium or aluminum interface, a method of mutually diffusing titanium and plating metal by heat treatment has been adopted. However, in the present invention, it has been found that the plating layer becomes brittle when the heat treatment is performed on the contrary, and the plating adhesion of the present invention is not deteriorated even without the heat treatment.

Using a light and high-strength titanium or titanium alloy and aluminum or aluminum alloy for the base material (core material) obtained in this way, a thick electrolytic Ni-P plating layer of HV500 or more and 100-1000 μm on the surface Since it is formed, excellent wear resistance can be exhibited. It is needless to say that a hard layer for imparting abrasion resistance is not required in a portion of the present composite material that does not contact the shaft. To further improve weight reduction,
It is advantageous to apply the covering only to the minimum necessary parts.

(Examples) Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 First, a method of manufacturing a composite material of a test material will be described.
The base material (core material) of electrolytic Ni-P plating is titanium alloy, Ti-
Using 6Al-4V, after performing degreasing → washing with water → etching → washing with water → surface activation treatment as described above, electrolytic Ni-P
Plated.

Plating bath _{composition, NiSO 4 · 6H 2 O:} 200g / l NiCl 2 · 6H 2 O: 50g / l H 3 PO 3: 4~40g / l H 3 PO 4: and 50 g / l, the current density, P In order to obtain a plated layer having a crystal orientation of <111> in an amount of 5 to 40 A / dm ² .

FIGS. 5 and 6 show X-ray diffraction patterns of Cu—Ni plating at each current density of 5 A / dm ² and 30 A / dm ² (Cu
Kα). In the diffraction pattern at a current density of 5 A / dm ² shown in FIG. 5, only a diffraction line having a plane index 111 of the crystal structure face-centered cubic lattice of the electrolytic Ni—P plating appears. In other words, FIG. 5 shows that there is no appearance of diffraction lines corresponding to plane indices 200 and 220 as shown in FIG. 6, and that the electrolytic Ni-P plating layer is made of crystals having selective orientation. And it can be seen that the electrolytic Ni-P plating layer has crystal orientation.

It was confirmed by analysis that the P content of this electrolytic Ni-P plating layer was 4% by weight or more.

The test material subjected to electrolytic Ni-P plating having these characteristics was subjected to a rolling wear test. Table 1 shows the results.
In the rolling wear test, the above-described rolling wear tester (FIG. 1) was used.

As is evident from Table 1, the electrolytic Ni-P plating layer of this example contains P by 4% by weight or more and has a crystal orientation, so that the adhesion to the base material is good, and As the thickness of the layer increases, the life in fatigue wear improves, and when the thickness of the plating layer becomes 100 μm or more, stable wear resistance is exhibited. Of course, a titanium alloy as it is without a plating layer is inferior in wear resistance.

On the other hand, since the comparative example has no crystal orientation, the wear resistance is inferior even if the thickness of the plating layer is large.

From the above results, the plating layer containing P by 4% by weight or more and having a crystal orientation is used as an inner layer, and a thicker electrolytic Ni-P plating is applied thereon as an outer layer, whereby the adhesion to the base material is improved. It is possible to form an electrolytic Ni-P plating layer having good rolling fatigue life.

Example 2 Example 2 is an example of two-layer plating of an inner layer and an outer layer.
The base material (core material) of P plating is titanium alloy, Ti-6Al-4V
As in Example 1, after performing degreasing → water washing → etching → water washing → surface activation treatment, electrolytic Ni-P plating was performed.

Plating bath _{composition, NiSO 4 · 6H 2 O:} 200g / l NiCl 2 · 6H 2 O: 50g / l H 3 PO 3: 4~40g / l H 3 PO 4: and 50 g / l, the current density is 5 to The plating bath composition and current density were appropriately selected so that the content was 40 A / dm ² and the P content was 4% by weight or more during the inner layer plating and the P content was less than 4% by weight during the outer layer plating.

These test materials were subjected to a rolling wear test. Table 2 shows the results. The rolling wear tester is the same as that of the first embodiment.

As is clear from Table 2, in the present invention example, since the P content of the inner layer is 4% by weight or more, the plating layer has a crystal orientation and the adhesion to the base material is improved. Shows abrasion resistance. Therefore, it can be seen that the composite material according to the present invention has excellent rolling fatigue life.

Example 3 Example 3 is an example of three-layer plating of an inner layer, an intermediate layer, and an outer layer. The base material (core material) of electrolytic Ni-P plating is titanium alloy,
Using Ti-6Al-4V, after performing degreasing → washing with water → etching → washing with water → surface activation treatment as in Example 1, electrolytic Ni-P plating was performed.

Plating bath _{composition, NiSO 4 · 6H 2 O:} 200g / l NiCl 2 · 6H 2 O: 50g / l H 3 PO 3: 4~40g / l H 3 PO 4: and 50 g / l, the current density is 5 to and 40A / dm ^2, depending on the desired P content and the thickness of each plating layer of the outer layer from the inner layer, was appropriately selected plating bath composition and current density.

These test materials were subjected to a rolling wear test. Table 3 shows the results. The rolling wear tester is the same as that of the first embodiment.

As is clear from Table 3, in the present invention example, the inner layer is plated with good adhesion to the base material described in Example 1, the P content is reduced in the intermediate layer and the outer layer more than the inner layer, and the plating thickness is reduced. Since the plating with increased thickness is applied, the toughness of the plating layer is improved, and a good rolling fatigue life is exhibited.

On the other hand, for some of the comparative examples, the P content of the inner layer was 4%.
Although the content is not less than weight%, the P content of the outer layer is large, so that the outer layer becomes brittle and the rolling fatigue life is inferior. Further, for a part, the rolling contact fatigue life is inferior because the P content of the inner layer is low and the P content of the outer layer is high.

Of course, it is obvious that the unalloyed titanium alloy is inferior in rolling contact fatigue resistance, but it is clear that WC spraying of HV1000 or more is also inferior to the above examples of the present invention.

Example 4 In Example 4, the crystal plane orientation of the electrolytic Ni-P plating of the outer layer was <11.
In this example, the integrated strength of 1> was set to 90% or less. The base material (core material) of electrolytic Ni-P plating was titanium alloy, Ti-6Al-4V, Ti-6.
Using Al-2Sn-4Zr-2Mo and Ti-6Al-6V-2Sn, after performing degreasing → water washing → etching → water washing → surface activation treatment as in Example 1, electrolytic Ni—P plating was performed.

Plating bath _{composition, NiSO 4 · 6H 2 O:} 200g / l NiCl 2 · 6H 2 O: 50g / l H 3 PO 3: 4~40g / l H 3 PO 4: and 50 g / l, the current density is 5 to It was 40 A / dm ^2, and the plating bath composition and the current density were appropriately selected according to the desired plating layer.

For these test materials, the crystal orientation, plating adhesion, and wear resistance were investigated. X for investigating crystal orientation
The X-ray diffraction was performed with a primary X-ray source of CuKα ray, 40 kV, 300 mA, a scanning speed of 4 ° / min, and an incident angle of 2 °, and the crystal orientation was [<111> / (<111> + <200> + <220 ＞ ＋ 〈311〉 ＋
<222>)] × 100.

The plating adhesion was evaluated by a tape peeling test after cutting 100 pieces of 1 mm cross cuts on the plating surface, bending them to a diameter of 5 mm and bending 180 °.

The wear resistance was investigated using the same rolling wear tester as in Example 1.

The results are shown in Tables 4-1 and 4-2 together with the P content and the thickness of the plating layer.

As is clear from Tables 4-1 and 4-2, the composite material obtained by subjecting the titanium alloy of the present invention to electrolytic Ni-P plating has a P content of less than 4% by weight and a crystal plane orientation <111>
Is 90% or less, the plating layer has excellent toughness and good wear resistance. The adhesiveness is good and the hardness is HV500 or more. Of course, the unplated base titanium alloy is inferior in wear resistance.

On the other hand, in the comparative example, since the P content is 4% by weight or more and the integrated intensity of the crystal plane orientation <111> is 90% or more, the plating layer becomes brittle and the wear resistance is poor.

In order to provide the desired rolling fatigue life characteristics in the composite material of the present invention, the adhesion of the plating layer to the base material, the toughness of the plating layer, and the hardness of the plating layer are important. Therefore, as described in the examples, the inner layer is made to have a P content of 4% by weight or more, the plating mainly having the crystal plane orientation <111> is performed, and the outer layer is made to have a P content of less than 4% by weight. Plane orientation <11
It is important to apply plating in which the integrated intensity of 1> is 90% or less.

(Effects of the Invention) As described above, according to the present invention, after adjusting the surface roughness of titanium or a titanium alloy and aluminum or an aluminum alloy, consistency between the crystal plane direction of the surface of the material to be plated and the crystal plane direction of plating is adjusted. In order to maintain the P content, the inner layer having a P content of 4% by weight or more, and further, in order to improve the toughness of the plating layer and secure wear resistance, the P content is less than 4% by weight, and the hardness is HV500.
At least two electrolytic Ni-P plating layers of the above outer layers are applied to titanium or a titanium alloy and aluminum or an aluminum alloy.

Therefore, the present invention is based on the fact that titanium and titanium alloy and aluminum and aluminum alloy which are light and high-strength are used as a base material and which are subjected to electrolytic Ni-P plating to provide titanium and titanium alloy and aluminum and aluminum alloy with wear resistance. Has an excellent effect of being able to impart the following.

[Brief description of the drawings]

Fig. 1 is a schematic diagram of the rolling wear test method, Fig. 2 is the rolling fatigue life of the WC film, electrolytic Ni-P plating and base metal, and Fig. 3 is the electrolytic Ni-P plating thickness and rolling fatigue. FIG. 4 is a diagram showing the relationship with the life, FIG. 4 is a model of rolling wear and the concept of contact pressure and shear force, and FIGS. 5 and 6 are X-ray diffraction patterns. 1 ... test piece 2 ... evaluation surface 3 ... ball bearing 4 ... bearing race 5 ... rotating shaft

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshinori Terada 5-10-17 Komatsubara, Arai-machi, Takasago-shi, Hyogo (56) References JP-A-61-170596 (JP, A) JP-A-59-185794 (JP) JP-A-58-147673 (JP, A) JP-A-1-106909 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C25D 5/00-7/12

Claims (4)

(57) [Claims] 1. The method according to claim 1, wherein the surface of titanium or a titanium alloy or aluminum or an aluminum alloy whose surface is Ra 0.5 μm or more and whose PPI ₅₀ is roughened to 130 or more has a P content of 4% by weight or more and a plating crystal plane orientation <111> as main layer and P content 4
A composite material for mechanical structure having excellent rolling fatigue life, characterized by being coated with at least two Ni-P plating layers of an outer layer having a plating hardness of HV500 or more at a weight percentage of less than 500%. 2. The composite material according to claim 1, wherein the concentration of P in the Ni—P plating layer changes continuously between the inner layer and the outer layer. 3. The crystal plane orientation <111> of Ni-P plating of an outer layer.
3. The composite material for a mechanical structure having excellent rolling fatigue life according to claim 1, wherein the integrated strength of the composite material satisfies the following expression. [<111> / (<111> + <200> + <220> + <311> + <222>)) × 100 ≦ 90 …… 4. The rolling fatigue life according to claim 1, wherein the surface of titanium or titanium alloy and aluminum or aluminum alloy is subjected to a surface roughening treatment with a solution containing a fluoride. Excellent mechanical structural composite