JP4517138B2 - Surface modifier for titanium substrate - Google Patents

Description

  The present invention relates to a surface modifier for a titanium base material, and more particularly, to a sliding system comprising a sliding member having a sliding surface as a titanium base material and an aqueous lubricant, and in particular, must be lubricated with water. Sliding systems and drive control systems for facilities and equipment in environments such as underwater and underwater where water resistance, corrosion resistance, and heat resistance are required, such as hydraulic operation equipment, water cooling equipment, marine equipment, underwater work equipment, and water systems The present invention relates to improvements in a machining system such as cutting, grinding, polishing, and plastic working using a working fluid, and a lubrication system for equipment used in an environment exposed to high temperature or open flame.

Generally, it is used in sliding systems in equipment and equipment under water and sea environments where water lubrication and water resistance, corrosion resistance, and heat resistance are required, such as water pressure operating equipment, water cooling equipment, etc. The sliding member is required to have corrosion resistance against water and seawater.
Titanium base materials such as titanium and titanium alloys are materials that have high mechanical strength, light weight, toughness, and corrosion resistance in water and seawater. If a titanium base material can be used as the sliding member in the moving system, the industrial merit is considered to be extremely large.
However, the titanium base material has a drawback in terms of wear resistance, lubricity resistance and the like because it easily causes adhesion at the sliding portion of the sliding system. For this reason, various methods for improving wear resistance by surface modification such as alloying or composite material containing other elements in the titanium base material have been proposed (Non-Patent Documents 1 to 4).

When the above surface-modified titanium-based material is rubbed in an environment where moisture is present, a thin titanium oxide layer is formed on the surface, and water reacts or adsorbs on this layer, so that Ti (OH) ₂ Titanium compounds having an OH group such as O and TiO ₂ · xH ₂ O are formed, and these titanium compounds having an OH group form a weakly bonded aggregate by hydrogen-water cross-linking. Since the aggregate of titanium compounds having OH groups acts as a lubricating film, low friction and low wear can be obtained.

However, when this surface-modified titanium-based material is used as a sliding member, TiO ₂ is caused to become a friction surface due to the progress of dehydration condensation of titanium compounds having OH groups or the oxidation reaction (tribo oxidation) induced by friction. However, there is a drawback that friction and wear gradually increase (Non-Patent Documents 5 to 8, Patent Document 1). For this reason, the improvement regarding this point was strongly desired.

Takenori Nakayama, Kaoru Kato, Wataru Urushibara, Yoshinori Terada, “Surface treatment technology for improving wear resistance of titanium”, Metal 66 11 (1996) 986-989. D. E. Alman, J. A. Hawk, "The abrasive wear of sintered titanium matrix-ceramic particle reinforced composite", Wear 225-229 (1999) 629-639. S. Ranganath, "A review on particulate-reinforced titanium matrix composite", J. Mater. Sci. 32 (1997) 1-16. Yuko Hibi, Yuji Enomoto, Harumichi Sato and Shinya Sasaki, "Titanium-Silicon-Nitrogen Composites with High Wear Resistance in Water and in Artificial Sea Water", J. Am. Ceram. Soc., 85 [9] (2002) pp2373- 75, Hibiko Yuko, Enomoto Yusuke, Sasaki Shinya, "Relationship between wear and surface chemical reaction of titanium composites", Surface Science, Vol.23, No.7, (2002) pp404-410 H. Mohrbacher, B. Blanpain, J. P. Celis and J. R. Roots, "The influence of humidity on the fretting behavior of PVD TiN coatings", Wear 180 (1995) 43-52. G. M. Kocher, T. Gross, E. Santner, "Influence of the testing parameters on the tribological behavior of self-mated PVD- coatings", Wear 179 (1994) 5-10. P. Q. Wu, H. Mohrbacher, C. P. Celis, "The fretting behavior of PVD TiN coatings in aqueous solutions", Wear 201 (1996) 171-177. Japanese Patent Laid-Open No. 10-45462

The present invention has been made in view of the circumstances as described above. For example, while an aggregate of titanium compounds having an OH group is present on the friction surface, low friction and low wear occur, but the condensation reaction proceeds. Overcoming the difficulty of transitioning to high friction and high wear because TiO ₂ precipitates on the friction surface due to wear and aggregate wear, tribo-oxidation, and the lubricity generated on the sliding surface of water-titanium material A titanium substrate that can provide a titanium substrate with excellent toughness, corrosion resistance, wear resistance, and lubricity even in an aqueous environment by stabilizing the titanium compound aggregate and suppressing the precipitation of TiO ₂ It is an object of the present invention to provide a sliding system comprising a surface modifying agent and a sliding member having a sliding surface containing the surface modifying agent as a titanium base.

The present inventors have considered the surface of a titanium base material in water or in the sea, for example, the behavior of the titanium base material in a sliding system composed of a sliding motion member having a sliding surface as a titanium base material and an aqueous lubricant. As a result of the investigation, when a small amount of alkoxysilane is added to the aqueous lubricant, the aggregate of titanium compounds formed on the sliding surface of the titanium surface can be captured as a more stable gel structure, and the sliding of the titanium base material can be performed. It has been found that the moving surface can be maintained in a good lubrication state with low friction and low wear, and the present invention has been completed.
That is, this application provides the following invention.
<1> A method for suppressing the precipitation of titanium oxide produced by tribooxidation in the presence of water on a sliding surface formed of a titanium base material and modifying the surface, wherein the sliding surface and characterized by processing while lubricating water containing alkoxysilane with an aqueous lubricant whose main component, method for reforming a sliding surface of the sliding member formed of a titanium substrate.
<2> The method for modifying a sliding surface of a sliding member according to <1>, wherein the precipitated titanium oxide is converted to an oligomer having an O—Ti—O—Si bond by alkoxysilane.
<3> The <1> or <2>, wherein the titanium base material is at least one selected from a titanium simple substance, a titanium compound composed of titanium and other different elements, a titanium alloy, and a titanium composite material. Of improving the sliding surface of the sliding member.
<4> A sliding member formed of a titanium base material obtained by the modification method according to any one of <1> to <3>.

Since the surface modifier of the titanium base material of the present invention is obtained by adding alkoxysilane to the water-based lubricant, the surface of the titanium base material is in a good lubricating state with low friction and low wear even in water or in the sea. Can be maintained. For example, a Ti-OH group of a titanium compound aggregate having an OH group formed on a sliding surface of a titanium-based material under water lubrication and a Si-OH group of an alkoxysilane hydrolyzate undergo a dehydration condensation reaction to produce O- Low friction due to the formation of a stable gel-like compound by forming Ti-O-Si bonds, etc., and maintaining the lubrication effect and suppressing the precipitation of TiO _{2 that} causes high friction and wear. -The effect of maintaining a low-abrasion lubrication state is exhibited. Therefore, the sliding system using the titanium base material containing the surface modifier of the present invention as a sliding surface is forced to be lubricated with water, and is required to have water resistance, corrosion resistance, and heat resistance. Sliding systems and drive control systems for facilities and equipment in environments such as underwater and underwater, such as hydraulic operating equipment, water cooling equipment, marine equipment, underwater work equipment, and processing machines such as cutting, grinding, polishing, and plastic working using aqueous processing fluids It can be suitably applied to a lubrication system for equipment used in an environment exposed to high temperatures or open flames. In addition, this surface modifier is used for mixing particulate matter in water, such as a surface of a portion in contact with a suspension of a mixer, a stirrer, a pulverizer, etc., which mixes, stirs or grinds solids using water as a dispersion medium. It can also be applied as a surface modifier for titanium-based materials that require wear resistance against abrasive wear due to impact.

The titanium substrate surface modifier of the present invention is characterized by adding alkoxysilane to a water lubricant.
The sliding system of the present invention is characterized in that in the sliding system comprising a sliding member having a sliding surface made of a titanium base material and an aqueous lubricant, the surface modifying agent is included.

  The water-based lubricant, which is the main component of the surface modifier of the present invention, means one that essentially contains water and does not substantially contain oil. As water, pure water, tap water, industrial water, seawater, river / lake water, groundwater and water containing other components such as alcohol, glycol, phosphate ester, aliphatic amine salt, etc. may be used. it can.

The surface modifier of the present invention is obtained by adding alkoxysilane to such an aqueous lubricant. The alkoxysilane of the general formula _{^{R 1 4-n Si (OR}} 2) n ( wherein, ^{R 1} represents an optionally substituted alkyl group, ^{R 2} represents an alkyl group, n is an integer of 1 to 4) Is preferably used. Examples of R ¹ include alkyl groups such as methyl, ethyl and propyl, and those alkyl groups substituted with functional groups such as amino group, amide group, carboxyl group, mercapto group, carbamide group, epoxy group and halogen. It is done. Examples of R ² include alkyl groups such as methyl, ethyl, and propyl.

Examples of such alkoxysilane include vinyltriethoxysilane, tris (2-methoxyethoxy) vinylsilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, and dimethoxy-3-mercaptopropylmethyl. Examples include silane, 3-aminopropyltriethoxysilane, 3- (2-aminoethylaminopropyl) dimethoxymethylsilane, and γ-ureidopropyltriethoxysilane. Among these, 3-aminopropyltriethoxysilane and 3- (2-aminoethylaminopropyl) dimethoxymethylsilane having a functional group such as an amino group, which are excellent in compatibility with water, are preferably used.
Although there is no special restriction | limiting in the use density | concentration of alkoxylane, 0.0001M-1M (water density | concentration) is preferable. Alkoxylane having an alkyl group substituted with this functional group is preferably used because of its excellent compatibility with water.
It is also possible to use a silanol precursor that generates silanol (Si-OH) in an aqueous medium. Examples of such silanol precursors include organic silicon compounds having hydrogen, halogen, acetoxyl group, amino group, cyano group, isothiocyan group, and isocyan group as functional groups directly bonded to silicon.
This surface modifier is not only applicable as a titanium substrate surface modifier used in the sliding system described below, but also a mixer, a stirrer, and the like for mixing, stirring or grinding solids using water as a dispersion medium. It can also be applied as a surface modifier for materials that require wear resistance against abrasive wear caused by collision of particulate matter in water, such as the surface of a portion that comes into contact with a suspension such as a pulverizer.

As the titanium base material forming the sliding surface used in the sliding system of the present invention, all conventionally known titanium base materials commonly used in this kind of field can be used. For example, titanium alone (pure titanium) Further, a titanium compound, a titanium alloy, a titanium composite material, or the like made of titanium and other different elements can be used.
Titanium compounds include TiN, TiC, TiAl, Ti ₃ Al, Ti ₅ Si ₃ , TiSi, TiSi ₂ , Ti _x Si _y N (0 <x <1, 0 <y <1), TiB ₂ , TiO ₂ A simple substance or a mixture of these may be titanium alloys such as Ti-6Al-4V, Ti-8Al-1V-1Mo, Ti-0.15Pd, Ti-6Al-2Sn-4Zr-2Mo-0.1Si. Those containing 1 to 6 elements of Cu, Pd, Sn, Al, V, Mn, Zr, Mo, Cr, Si, and Fe in the range of 0.1 to 20%, respectively, are pure titanium composite materials. A material containing 0.1 to 50% of a titanium compound as a reinforcing material in a titanium or titanium alloy substrate and graphite, Si ₃ N in a substrate made of at least one of pure titanium, titanium compound and titanium alloy ₄ , SiC, BN, Al ₂ O ₃ , ZrO ₂ , WC, AlN, B ₄ C, MoS ₂ etc. .

The sliding member of the present invention is usually composed of a combination of a stationary side sliding member and a movable side sliding member, and one or both sliding surfaces of these sliding members are formed of the above-described titanium substrate. It only has to be. Further, the portion other than the sliding surface may be formed of the titanium base material, and other base materials such as ceramic material, glass material or polymer material, Fe, Cu, Au, Al, Mg , Ni, Pt, Pd, Zn, Pb, Si, Zr alone or an alloy or intermetallic compound mainly composed of these elements, or a composite material, a functionally gradient material, a coating material, a multilayer structure material, etc. May be.
The sliding system comprising a combination of a stationary sliding member and a movable sliding member applicable in the present invention includes, for example, a hydraulic pump cylinder block and piston, shaft and bearing, cylinder block and valve plate, shoe and thrust. Examples include a plate, a sleeve and a spool of a water pressure control valve, a seat ring and a driven ring of a mechanical seal of a water cooling device, and the like.

  In the sliding system using the sliding surface of the present invention based on a titanium base, by using a surface modifier formed by adding alkoxylane to the water lubricant, the sliding surface has low friction and low wear. It is presumed that the good lubrication state is maintained for the following reason.

As described above, when the titanium-based material is rubbed in an environment where moisture is present, a thin titanium oxide layer is formed on the surface, and water reacts or adsorbs on this layer, whereby Ti (OH) ₂ O and Titanium compounds with OH groups such as TiO ₂ and xH ₂ O are generated, and these titanium compounds with OH groups form weakly bonded aggregates due to hydrogen-water crosslinks that act as lubricating films. However, when this is used as a sliding member, TiO ₂ is deposited on the friction surface due to the progress of dehydration condensation of the titanium compound having an OH group or the oxidation reaction (tribo-oxidation) induced by friction. Friction and wear are significantly increased. In contrast, in the present invention, since an alkoxysilane is added to the water-based lubricant, the titanium compound having an OH group, which is preferably produced as a lubricating film, is generated on the sliding surface of the titanium-based material under water lubrication. A stable gel-like structure with a long-lasting lubrication effect by dehydrating and condensing the Ti-OH groups of the aggregate with Si-OH groups of the alkoxysilane hydrolyzate and converting them to O-Ti-O-Si bonds. In addition, since it is possible to suppress the precipitation of TiO _{2 that} causes high friction and high wear, it is possible to maintain a low friction and low wear lubricating state satisfactorily.

  The sliding system of the present invention is required to be lubricated with water and is required to have water resistance, corrosion resistance, and heat resistance. Lubricating systems for operating equipment, water cooling equipment, marine equipment, underwater work equipment, processing machines using water-based machining fluid, grinding, polishing, plastic working, and equipment used in environments exposed to high temperatures and open flames Etc., and can be suitably applied.

  Hereinafter, the present invention will be described in more detail with reference to examples.

[Production of model sliding member]
The raw material powder having the composition shown in Table 1 was placed in a silicon nitride pot together with silicon nitride balls using n-hexane as a dispersion medium, and stirred for 30 minutes in a planetary ball mill. After stirring, n-hexane was volatilized to obtain a mixed powder. A mixed-powder powder is packed in a graphite mold and sintered in an SPS (discharge plasma sintering method) under vacuum at a pressure of 650 Kg / cm ² (64 MPa) at a temperature of 1300 ° C or 1400 ° C. Was made. The obtained sintered disk was made parallel by a surface grinder and then polished in order by a No. 400 and No. 1000 grinder.

[Preparation of aqueous alkoxysilane solution]
The alkoxysilanes used as additives are shown in Table 2. An alkoxysilane aqueous solution was obtained by adding alkoxysilane corresponding to 0.0001M, 0.001M, 0.01M, and 0.1M by volume molar concentration in distilled water and then stirring.

[Evaluation of lubricity]
Lubricity was evaluated from the coefficient of friction and specific wear. In the lubricity evaluation test, a ball-on-disk type rotary friction tester (ISC-200PC tribometer) was used. A hemispherical pin (2mm radius) of the same type as the disk material in an alkoxysilane aqueous solution with a concentration of 0.0001M to 0.1M, with a friction speed of 40mm / s and a load of 2.5gf (0.0245N) or 50gf (0.49N) Friction with time was performed, and the coefficient of friction and specific wear were measured. This lubricity evaluation test was conducted according to FIG. In this experiment, the specific wear amount of the pin and the disk was obtained from the following equation.
[Specific wear amount, mm ³ / Nm] = [Wear volume, mm ³ ] / {[Friction distance, m] × [Load, N]}
However, the pin wear volume is the volume of the wear portion 1 in FIG. 2 and is given by V = (1/3) πh ² (3r-h). The disk wear volume is the volume of the wear portion 2 in FIG. 3 and is given by V = 2πr′A. The sum of the specific wear amount of the pin and the specific wear amount of the disk was taken as the total specific wear amount.

Table 3 shows the results in the alkoxysilane aqueous solution in the present invention.
As a comparative example, the same test as in Examples 1 to 23 was performed except that distilled water was used instead of the alkoxysilane solution, and the friction coefficient and the specific wear amount were measured. The results are shown in Table 4.

FIG. 4 shows a graph of the change of the friction coefficient with respect to the sliding distance in Comparative Example 3 and Example 9. In Comparative Example 3, the friction coefficient suddenly increased immediately after the start of the friction test and became a high value of about 0.8. However, in Example 9, the increase in the friction coefficient in the initial stage of the friction test was small and stabilized at a low value of 0.27. The coefficient of friction is shown.
From Table 3, Table 4 and FIG. 4, it was shown that in the alkoxysilane aqueous solution, both the friction coefficient and the specific wear amount are reduced as compared with water. From the above results, it was found that the water lubricity of the titanium-based material was improved in the aqueous solution to which the alkoxysilane of the present invention was added, compared to the case of no addition.

Explanatory drawing of the lubricity evaluation test according to the present invention Explanatory drawing of measuring method of pin wear volume Illustration of how to measure the wear volume of a disc The graph of the change of the friction coefficient with respect to the sliding distance of Example 9 and Comparative Example 3

Claims (4)

Titanium oxide produced by the presence Tribo oxy retardation of water, to prevent the deposits on the sliding surface formed by the titanium substrate, a method of modifying the surface, the sliding sliding surface, alkoxy A method for modifying a sliding surface of a sliding member formed of a titanium base material, wherein the treatment is performed while lubricating with an aqueous lubricant containing silane and water as a main component .   The method for modifying a sliding surface of a sliding member according to claim 1, wherein the precipitated titanium oxide is converted into an oligomer having an O-Ti-O-Si bond by alkoxysilane.   3. The sliding member according to claim 1, wherein the titanium base material is at least one selected from a titanium simple substance, a titanium compound composed of titanium and other different elements, a titanium alloy, and a titanium composite material. Sliding surface modification method.   The sliding member formed with the titanium base material obtained by the modification | reformation method in any one of Claims 1-3.

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