JP2690598B2 - Method of forming a film with excellent heat and wear resistance and sliding resistance on titanium or titanium alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] Titanium or titanium alloys are used for functional parts aiming at weight reduction of engine valves, rocker arms, valve retainers, connecting rods, crankshafts, etc. of automobiles and motorcycles, and corrosion resistance. The use for pump parts for the chemical industry is expanding. These titanium alloys are often desired to have heat resistance, wear resistance and sliding resistance.

The present invention relates to a method for forming a film having excellent heat resistance, wear resistance, and sliding resistance on titanium or a titanium alloy.

[Prior Art] As a method of forming a film on titanium or a titanium alloy, there are a gas nitriding method and a salt bath nitriding method. However, since the nitriding method has a high treatment temperature, it is difficult to use until the treatment because it is largely deformed by thermal strain, and further, it takes a long time to obtain a hardened layer, so that the productivity is low.

There are also dry plating methods such as ion plating, CVD, PVD and various wet plating methods. With these plating methods,
There is a problem that the adhesion between titanium or a titanium alloy and the formed film is low, and the film peels off during use.

Japanese Unexamined Patent Publication (Kokai) No. 64-79397 discloses a method of forming a wear-preventing layer on titanium or titanium alloy by a method of Martin Thoma. In this method, Because it is heat treated in an oxidizing atmosphere,
There is a problem that the nickel film formed by the chemical deposition method is oxidized and the formed film must be removed when the chromium film is formed by the electroplating method in the next step. The chromium film formed as the wear resistant layer has a problem that the seizure resistance is insufficient.

[Problems to be Solved by the Invention] The present inventors have invented a method for forming a film having excellent heat resistance and wear resistance on titanium or a titanium alloy, and have already applied for a patent in Japanese Patent Application No. 2-30494. did.

As a result of further research, the present inventors have invented a method for forming a film on titanium or a titanium alloy, which has excellent heat resistance and wear resistance, and further has excellent sliding resistance. That is, the present invention provides a coating having heat resistance, wear resistance, and sliding resistance.
It is an object to disclose a method of forming titanium or a titanium alloy. The titanium or titanium alloy on which the film of the present invention is formed is also excellent in sliding resistance, and in combination with its excellent heat resistance and wear resistance, it can be used in a wider field of use.

[Means for Solving the Problems] In the first step of the present invention, the surface of titanium or a titanium alloy is cleaned by pickling. This cleaning can be achieved, for example, by performing shot blasting with alumina particles, followed by pickling with, for example, about 15% hydrochloric acid at room temperature for about 30 seconds and then with water. If the surface is cleaned by pickling, and particularly by using hydrochloric acid, the adhesion of strike plating in the next step becomes good. For example, when an oily substance is attached to the surface, the oil content is removed in advance by washing with an alkali or an organic solvent such as trichlene vapor before the shot blasting treatment.

In the second step of the present invention, in titanium or titanium alloy,
Strike plating of copper or nickel. The strike plating is performed to form a dense film having excellent adhesion on the surface of titanium or titanium alloy. For copper strike plating, for example, a solution of copper sulfate 60 g /, Roussel salt 160 g /, caustic soda 50 g / at room temperature is used, and for nickel strike plating, for example, nickel chloride 100 g /, hydrochloric acid 30 g / at room temperature is used. It is obtained by electroplating.

According to the findings of the present inventors, the thickness of the strike plating film is appropriately 1 to 5 μm. If the thickness is 1 μm or less, it is difficult to completely cover the surface of titanium or titanium alloy with the strike film due to the variation of the film thickness. On the other hand, when the thickness is 5 μm or more, the processing time becomes long, which is not economical.

In the third step of the present invention, nickel electroplating or nickel-phosphorus electroplating is applied on the strike plating.

Nickel electroplating uses a plating solution containing, for example, nickel sulfamate 800 g /, nickel chloride 15 g /, boric acid 30 g /, and nickel-phosphorus electroplating, for example, nickel sulfamate 800 g /, nickel chloride 15 g /, boric acid. It can be obtained by electroplating using a plating solution containing 30 g / acid and 3 g / sodium hypophosphite. According to the knowledge of the present inventors, the thickness of the electroplating film formed in the third step is preferably 5 to 20 μm. As will be described later, in the present invention, vacuum heating, formation of a wear-resistant coating, and formation of a solid lubricating coating are further performed. However, by setting the thickness of the electroplating coating in the third step to 5 to 20 μm, the adhesion can be improved. A film with good heat resistance, wear resistance and sliding resistance is formed.

The nickel electroplating film has a sufficient hardness up to about 200 ° C, and the nickel-phosphorus composite electroplating film has a sufficient hardness up to about 350 ° C. In the present invention, either nickel electroplating or nickel-phosphorus electroplating is selected in consideration of the wear resistant coating in the treatment for forming the wear resistant coating described later.

In the fourth step of the present invention, a vacuum heat treatment is performed in which the degree of vacuum is in the range of 10 ^-1 to 10 ^-5 torr and heating is performed at least 450 ° C for 1 hour or more. If the degree of vacuum is 10 ^-1 torr or less, there is a risk that the film formed up to the second step will be oxidized, while obtaining a degree of vacuum of 10 ^-5 torr or more is costly and uneconomical. This vacuum heat treatment is performed to form a titanium / nickel alloy layer of Ti ₂ Ni, TiNi, TiNi ₃ or a titanium / copper alloy layer of TiCu, TiCu _2, etc., but to form these metal layers. Is preferably heated at least at 450 ° C. for 1 hour or more. Cooling after heating in vacuum, particularly in the high temperature range, is preferably performed while maintaining the above vacuum degree. When cooled in an oxidizing atmosphere, the surface is oxidized and the treatment time becomes longer in the surface activation treatment described later. When this vacuum heating and cooling under vacuum are performed, an alloy layer having excellent adhesion is formed without being oxidized, so that in the surface activation treatment described later, as described in JP-A-1-79397. Excessive film removal is unnecessary, and a heat-resistant and abrasion-resistant film described later is formed by a simple surface activation treatment.

The surface activation treatment is carried out in the fifth step of the present invention, but as mentioned above, this surface activation can be achieved by a simple method, for example, by immersing in a nitric hydrofluoric acid solution containing 5% hydrofluoric acid. By this surface activation treatment, the preformed film formed up to the fourth step is retained, and the preformed film is slightly etched to improve the adhesion with the heat resistant and abrasion resistant film formed in the subsequent sixth step. Increase. According to the knowledge of the present inventors, it is suitable to contact with an aqueous solution containing 3 to 10% hydrofluoric acid and 50 to 70% nitric acid for 2 to 5 seconds.

In the sixth step of the present invention, a heat resistant and abrasion resistant film is further formed. This heat and wear resistant coating is composed of SiC, Si ₃ N ₄ , Al ₂ O ₃ , WC, ZrB ₂ ,
It is a nickel-phosphorus alloy or cobalt film in which one or more fine powders selected from fine ceramics such as diamond and CrB are dispersed in a matrix. The matrix is a nickel-phosphorus alloy heat and wear resistant coating,
For example, nickel sulfamate 800g /, nickel chloride 1
A solution of 5g /, boric acid 30g /, sodium hypophosphite 3g /, and a heat-resistant wear-resistant coating with cobalt as the matrix,
For example, in a solution of cobalt sulfamate 300 g /, cobalt chloride 15 g /, and boric acid 30 g /, the average particle size is 1
It can be obtained by adding 200g / of 1 or 2 or more fine powders selected from SiC, Si ₃ N ₄ , Al ₂ O ₃ , WC, ZrB ₂ , CrB, and diamond of μm, and electroplating this as an electrolytic solution. . The particle size of the fine powder used when forming the heat resistant and abrasion resistant film is suitably 0.1 to 10.0 μm. If it is 0.1 μm or less, abrasion resistance and sliding resistance are not sufficient, and if it is 10.0 μm or more, it is difficult to disperse it uniformly in the matrix. The thickness of the heat and abrasion resistant film is preferably 5 μm to 500 μm. If it is 5 μm or less, the performance as an abrasion resistant film is insufficient, and if it is 500 μm or more, it is not practical.

As a matrix, nickel-phosphorus alloy precipitates Ni ₃ P and hardens due to temperature rise up to about 350 ° C.
In addition, cobalt does not decrease in hardness even at a high temperature of about 500 ° C. In the present invention, fine powder of phi ceramics is dispersed in a matrix, for example, 2 to 20% by weight. The fine powder to be dispersed is a high-hardness fine powder such as SiC (micro hardness about 3000), Si ₃ N ₄ (micro hardness about 2000), WC (micro hardness about 2500) and diamond (micro hardness about 8000). By dispersing these fine powders in the matrix, sufficient abrasion resistance is exhibited during sliding.

In the seventh step of the present invention, the surface of the heat and wear resistant film is coated with Rz:
Roughening treatment with a surface roughness of 1.0 to 10.0 μm is performed. This roughening treatment is, for example, 120 to 2 by a dry method or a wet method.
It is obtained by projecting No. 70 alumina particles on a heat and wear resistant film. By this surface roughening treatment, a solid lubricating film, which will be described later, having sufficient adhesiveness and holding property can be formed on the heat resistant and abrasion resistant film. When Rz is less than 1.0 μm, the solid lubricant coating has insufficient adhesion and retention. Further, even if Rz exceeds 10.0 μm, there is no difference in adhesion and holding property of the solid lubricating film from that in the case of 10.0 μm, and considering the dimensional tolerance of the product, 10.0 μm or less is preferable.

In the eighth step of the present invention, after the roughening treatment, the Mo
Form and bake a solid lubricating coating containing one or more selected from S ₂ , graphite, boron nitride and fluororesin. The roughened surface is cleaned by, for example, alkali cleaning or organic detergent cleaning, and MoS ₂ , graphite, boron nitride or fluororesin is applied by a spray method or a dipping method, and this is heated to, for example, 180 ° C. And bake to form a solid lubricating film. According to the knowledge of the present inventors, when the thickness of the solid lubricating coating is 5 to 30 μm, the surface has excellent sliding resistance over a long period of time.

[Operation] The reason why the film formed by the present invention is excellent in heat resistance will be described. The matrix of the heat and abrasion resistant film specified in the sixth step of the present invention is a nickel-phosphorus alloy or cobalt having heat resistance. Further, all of the solid lubricating coatings specified in the eighth step can withstand a high temperature of about 400 ° C. While sliding, the temperature of titanium or titanium alloy rises, but the coating of the present invention has heat resistance sufficient to withstand this rise in temperature, as described above.

The reason why the film formed by the present invention has excellent wear resistance will be described. The heat resistant and abrasion resistant coating specified in the sixth step of the present invention contains fine powder of high hardness. For example Si
C has a micro hardness of about 3000, Si ₃ N has a micro hardness of about 2000, WC has a micro hardness of about 2500, and diamond has a micro hardness of about 8000.
A film in which these fine powders of extremely high hardness and high hardness are dispersed covers titanium or a titanium alloy. Therefore, the coating film of the present invention has excellent wear resistance.

The reason why the film formed by the present invention is excellent in sliding resistance will be described. In the present invention, unevenness is formed on the surface by the roughening treatment specified in the seventh step, and the solid lubricating coating specified in the eighth step of the present invention is formed on the surface having the unevenness. At this time, the solid lubricating film is formed with strong adhesion strength due to the wedge effect of the uneven shape. Further, during sliding, the solid lubricant is embedded in the recesses and is not removed even when sliding under a high surface pressure. As described above, the sliding surface of the present invention always contains MoS ₂ , graphite, and boron nitride that reduce the sliding friction coefficient. Therefore, the sliding resistance is improved and the occurrence of seizure is prevented even after long-term use.

As described above, the film formed on the titanium or titanium alloy of the present invention has excellent heat resistance, wear resistance, and sliding resistance, but these excellent performances indicate that the adhesion of the formed film is extremely excellent. It is an effect that is brought about by being present. That is, the adhesion with titanium or titanium alloy is brought about by the first step of pickling and the second step of strike plating. Excellent adhesion is also brought about by the formation of the electroplating film in the third step and the vacuum heating in the fourth step. That is, titanium or titanium alloy forms an alloy layer with the electroplated metal without being oxidized by vacuum heating. Further, the surface activation treatment of the fifth step forms the heat resistant and abrasion resistant coating of the sixth step with a strong adhesion, and the surface roughening treatment of the seventh step forms a solid lubricating coating having good adhesion.

The operation of the present invention will be described more specifically. The inventors of the present invention conducted a Falex wear test under dry conditions using a test piece obtained by subjecting a pin material of Ti-6Al-4V alloy (diameter 10 mmφ) to various treatments shown in Table 1. The block material used in the test is SUJ-2 (hardness HRC60, 90 ° V type). The seizure limit load in Table 1 and the sliding friction coefficient in FIG. 1 are the results.

No. 1 in Table 1 is a test piece which was not subjected to coating treatment at all, but as shown in FIG. 1, seizure occurred immediately after the start of the test.

No. 2 to No. 5 in Table 1 were formed by the method of Japanese Patent Application No. 2-30494. That is, No. 2 is pickled, copper strike plated, nickel-phosphorus electroplated, vacuum heat treated at 10 ^-3 torr at 500 ° C for 3 hours, and formed with a heat-resistant and abrasion-resistant film of nickel-phosphorus and SiC. The test piece with a thickness of 20 μm, No3, the heat and wear resistant coating is nickel phosphorus and Si ₃ N ₄ ,
Others are the same test pieces as No. 2 No. 4 is the same heat resistance and wear resistant coating as cobalt and ZrB _2. Others are the same as No. 2 No. 5 is the same heat resistance and wear resistant coating as cobalt and SiC.

No. 2 to No. 5 did not form the solid lubricating film according to the seventh and eighth steps of the present invention, so that the sliding friction coefficient was 0.12 as shown in FIG. It is as large as ~ 0.15, and the seizure limit load is as small as 65 kg or less as seen in Table 1.

No. 6 is an example in which only the solid lubricating coating was formed without forming the heat resistant and abrasion resistant coating of the present invention. That is, Ti-6Al-4
The V alloy is shot blasted with No. 220 alumina particles, washed with an organic solvent, and a solid lubricant film of FBT-116 (phenol resin film containing the MoS ₂ particles, manufactured by Kawamura Laboratory Co., Ltd.) containing 10 μm is sprayed by a spray method. Is a test piece coated to a thickness of 1 and dried at 180 ° C. for 1 hour. As mentioned above, No. 6 is a test piece coated with a diameter solid lubricant film without forming a heat and wear resistant film. However, as shown in Fig. 1 and Table 1, since the material surface hardness is low, the block load is 65 kg.
The seizure has occurred. As described above, the solid lubricating film has no effect unless it is applied to a high hardness surface.

No. 7 to No. 10 in Table 1 and FIG. 1 are test pieces according to the method of the present invention. That is, No. 7 is a test piece on which a heat and wear resistant film was formed by the method of No. 2 and further roughened to form a solid lubricating film of FBT-116 with a thickness of 10 μm. This is a test piece with a wear film formed and further roughened to form a solid lubricant film of FBT-116 with a thickness of 10 μm. No9 is a heat resistant wear resistant film formed by the method of No4. Is a test piece on which a solid lubricating film of FH-70 (made by Kawamura Laboratory, which contains epoxy resin film containing fluorine resin) with a thickness of 10 μm was formed by heat treatment. Test of forming a wear film and further roughening the surface to form a solid lubricant film of HMB-4A (polyimide resin film containing MoS ₂ particles, Kawamura Laboratory Co., Ltd.) with a thickness of 10 μm It's a piece.

Since the test pieces No7 to No10 made by the method of the present invention are a combination of the heat resistant and abrasion resistant coating and the solid lubricating coating, the sliding friction coefficient at a block load of 200 kg or more is about 0.02 to 0.04 as shown in FIG. It is extremely small and has a seizure limit load of 715 to 780 kg as shown in FIG. 1 and Table 1, and has extremely excellent sliding resistance.

[Examples] Example 1 Treated material: surface treatment of pin material of a Falex wear test piece, 6Al-4V-Ti (10mmφ, 35mmL) pin material 1. Shot blast treatment with alumina particles of grid No. 220 2. Organic Solvent cleaning (Triclin steam cleaning) 3. Alkaline degreasing treatment (FC-315, weak alkaline cleaner manufactured by Nippon Parkerizing Co., Ltd.), 50 gr /, 70 ° C, 3 minutes immersion 4. Washing with water 5. Pickling with hydrochloric acid (17%), room temperature , 30 seconds 6. Washing with water 7. Copper strike plating bath composition Copper sulfate 60gr /, Rossel salt 160gr / Caustic soda 50gr / Treatment temperature Normal temperature, Current density 0.5A / dm ² Coating thickness 2μm 8. Washing 9. Nickel-phosphorus alloy plating Treatment bath composition Nickel sulfamate 800gr / Nickel chloride 15gr /, Boric acid 30gr / Sodium hypophosphite 3gr / Treatment temperature 57 ℃ Current density 15A / dm ² Film thickness 10μm 10. Washing 11. Hot air drying (about 80 ℃) 12 . vacuum heat treatment vacuum 10 ^-3 Torr, a treatment temperature 500 Treatment time 3 hours, 13. activation treatment liquid HF 5%, HNO ₃ 60% normal temperature, 3 seconds immersion 14. washing 15. Nickel-phosphorus-SiC composite plating bath composition nickel sulfamate 800Gr / nickel chloride 15 gr / boric acid 30gr / Sodium hypophosphite 3gr / SiC 200gr / Treatment temperature 57 ℃ Current density 15A / dm ² Film thickness 20μm 16. Water washing 17. Hot air drying (about 80 ℃) 18. Grid 200 shot blasting with alumina particles 19. Organic Solvent cleaning (tricklene vapor cleaning) 20. Solid lubricant film treatment Spray method, FBT-116 (Defric Coat) 10 μm 21. Drying (180 ° C, 1 hour) Example 2 The same treatment material as in Example 1 surface treatment of pin material 1. to 14. are the same as in Example 1. 15. Cobalt / SiC composite plating treatment Bath composition Cobalt sulfamate 300gr / Cobalt chloride 15gr / Boric acid 30gr / SiC 200gr / Treatment temperature 57 ° C Current density 15A / dm ² Coating thickness 20μm 16 . ~ 21. Are the same as in Example 1 Comparative Example 1 Shot blasting Example 1 by surface treatment 1. Alumina particles of the grid 220 No. same pin member 2. Organic solvent cleaning (trichlorethylene vapor cleaning) 3. Solid lubricating film processing examples 1,20 to the same. Spray method, FBT-116 (Defric C
oat) 10 μm 4. Drying (180 ° C., 1 hour) Reference Example 1 The treatment material is the same as in Example 1.

Surface treatment of pin material The method of Japanese Patent Application No. 2-30494, 1. to 17. The same as in Example 1. Nickel-Phosphorus-SiC composite plating film The films formed on the pin materials in the above examples, comparative examples, and reference examples were combined with SUJ-2 (hardness HRC60) block material, and dry conditions without oil lubrication The Falex wear test was carried out to measure the seizure limit load (Table 2) and the history of the sliding friction coefficient (Fig. 2). The results are shown below.

Comparative example 1 has a block load of 320 kg, and reference example 1 has 256 kg.
Seizure occurred in the film, but with the films formed by the method of the present invention (Examples 1 and 2), the seizure limit load can be improved to 1000 kg or more, and the sliding friction coefficient is also high under load. Shows as small as 0.02 to 0.03 and shows excellent slidability.

[Effects of the Invention] As described above, the film formed according to the present invention can surprisingly reduce the sliding friction coefficient even under sliding under dry conditions without oil lubrication, and has seizure resistance. It is a film with excellent sliding properties that can improve the

By applying the method of the present invention, it is possible to apply titanium or a titanium alloy to a sliding member that cannot use oil-based lubrication, and it is required to be lightweight and have high load performance including automobile parts. Especially effective when used for.

[Brief description of the drawings]

FIG. 1 is a diagram showing the result of a Falex wear test under dry conditions. FIG. 2 is a diagram showing the result of a Falex wear test in Examples.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A 59-126773 (JP, A) JP-A 1-159358 (JP, A) JP-A 64-79397 (JP, A) JP-A 53- 11131 (JP, A) JP 63-78741 (JP, A) JP 61-87894 (JP, A) JP 53-18436 (JP, A) JP 2-70073 (JP, A) Japanese Patent Publication Shou 45-12202 (JP, B1)

Claims (7)

(57) [Claims] 1. A method for forming a film having excellent heat resistance, wear resistance and sliding resistance on titanium or a titanium alloy, which comprises subjecting the surface of titanium or a titanium alloy to the following treatments in the order given. Pickling, strike plating of copper or nickel, nickel electroplating or nickel-phosphorus electroplating film formation, vacuum heating to heat at least 450 ° C for 1 hour or more in a vacuum range of 10 ^-1 to 10 ^-5 torr Treatment, surface activation treatment, the matrix is nickel-phosphorus alloy or cobalt and SiC.Si ₃ N ₄ .Al ₂ O ₃ .WC.ZrB ₂ ..
Diamond.CrB, one or more kinds of fine powder dispersed, heat-resistant and abrasion-resistant film forming treatment, Rz: 1.0-1
Roughening treatment with a surface roughness of 0.0 μm, MoS _2. Graphite. Boron night ride. Forming and baking treatment of a solid lubricating coating containing one or more selected from fluororesins. 2. Copper or nickel strike plating,
Strike plating having a thickness of 1 to 5 μm, wherein the titanium or titanium alloy according to claim (1) has heat and wear resistance,
A method of forming a film with excellent sliding resistance. 3. The titanium or titanium alloy according to claim 1, wherein the nickel electroplating or nickel-phosphorus electroplating coating is an electroplating coating having a thickness of 5 to 20 μm. A method of forming a film with excellent mobility. 4. The surface activation treatment comprises leaving to cool under reduced pressure and then treating with an aqueous solution containing 3 to 10% hydrofluoric acid and 50 to 70% nitric acid for 2 to 5 seconds. Processing,
A method of forming a film having excellent heat resistance and wear resistance and sliding resistance on the titanium or titanium alloy according to claim (1). 5. The fine powder used for forming the heat and wear resistant film is a fine powder having an average particle size of 0.1 to 10.0 μm, and the heat and wear resistant film is a heat resistant and wear resistant film having a thickness of 5 μm to 50 μm. Method for forming a film having excellent heat resistance and wear resistance and sliding resistance on titanium or titanium alloy according to item (1) 6. The titanium or titanium alloy according to claim 1, wherein the surface-roughening treatment is a surface-roughening treatment in which alumina particles of a 120-270 grid are projected by a dry method or a wet method. A method of forming a film with excellent heat resistance, wear resistance, and sliding resistance. 7. The titanium or titanium alloy according to claim 1, wherein the solid lubricating coating is a solid lubricating coating having a thickness of 5 to 30 μm, and which has excellent heat and wear resistance and sliding resistance. How to make.