Sliding member

Abstract

A sliding member 10 comprises: a base material 11; and a sliding alloy part 12 that is provided on the surface 13 of the base material 11, that is a Cu-based alloy mainly composed of Cu, and that is formed from a set of a plurality of unit alloy parts 12A-12E. The sliding alloy part 12 includes a first soft phase 31 existing in a boundary region 22 defined within a preset range with reference to a unit interface 21, and a second soft phase 32 existing in a region excluding the boundary region 22. When the total area proportion of the first soft phase 31 included per unit area is defined as a first area proportion S1, and the total area proportion of the second soft phase 32 included per unit area is defined as a second area proportion S2, the sliding alloy part 12 satisfies S1<S2.

Description

Cross - reference to related applications

[0001] This application is based on Japanese Application No. 2023 - 061455 filed on April 5, 2023, the content of which is incorporated herein by reference.

Technical Field

[0002] This disclosure relates to a sliding member.

Background Art

[0003] For example, in an axial sliding member, a sliding alloy portion that slides against a mating member is provided on the surface of a base material. This sliding alloy portion is provided integrally with the base material by attaching a separate member, for example, by laser welding or sputtering. When forming a sliding alloy portion by attaching a separate member to the base material, since it is easy to control the alloy structure and composition of the separate member, it is easy to ensure the desired sliding performance for the sliding alloy portion. On the other hand, when the base material and the sliding alloy portion are composed of separate members in this way, it is not easy to ensure the desired sliding characteristics for the sliding alloy portion as wear progresses. Also, when the base material and the sliding alloy portion are separate members, there is a possibility of slippage occurring at the interface between the outer peripheral surface of the sliding member provided with the sliding alloy portion and the housing to which the sliding member is attached. Therefore, it has been considered to form a sliding alloy portion on the surface of the base material by welding (see Patent Document 1).

[0004] However, in the case of Patent Document 1, although forming a sliding alloy portion by welding is disclosed, the alloy structure and composition of the sliding alloy portion are not strictly controlled. Therefore, it is difficult to strictly control the alloy structure and composition of the sliding alloy portion. As a result, the sliding alloy portion formed by welding as in Patent Document 1 has a problem that it is difficult to improve sliding characteristics such as fatigue resistance.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] Therefore, the objective is to provide a sliding member in which the sliding alloy part formed by welding is controlled to improve the sliding properties. [Means for solving the problem]

[0007] A sliding member according to one embodiment comprises a base material and a sliding alloy portion provided on the surface of the base material and formed by a collection of multiple unit alloy portions of a Cu-based alloy mainly composed of Cu. The sliding alloy portion includes a first soft phase existing in a boundary region defined in a range predetermined with respect to the unit interface of the unit alloy portion, and a second soft phase existing in the region of the unit alloy portion excluding the boundary region. When the ratio of the total area of ​​the first soft phase contained per unit area is defined as the first area ratio S1 and the ratio of the total area of ​​the second soft phase contained per unit area is defined as the second area ratio S2, then S1 <S2である。

[0008] The sliding alloy portion formed by welding is composed of a collection of multiple unit alloy portions. In this embodiment, the sliding member specifies the proportion of a first soft phase present in a boundary region defined within a predetermined range based on the unit interface, which is the interface of the unit alloy portions, and the proportion of a second soft phase present in the region excluding this boundary region. The total area proportion of the first soft phase present in the boundary region is smaller than that of the second soft phase present in the other regions. As a result, crack propagation in the sliding alloy portion is reduced, especially in the boundary region near the interface of the unit alloy layers. Therefore, sliding properties such as fatigue resistance can be improved. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic diagram showing the configuration of a sliding member according to one embodiment. [Figure 2] A schematic diagram showing the configuration of a sliding member according to one embodiment. [Figure 3] A schematic cross-sectional view showing a sliding member according to one embodiment. [Figure 4] A schematic diagram showing an enlarged view of section IV in Figure 1. [Figure 5] A schematic cross-sectional view showing an example of applying a sliding member according to one embodiment. [Figure 6] A schematic diagram showing a welding apparatus for manufacturing a sliding member according to one embodiment. [Figure 7] A schematic diagram showing an evaluation of an example and a comparative example of a sliding member according to one embodiment. [Figure 8] A schematic diagram showing the conditions for a fatigue strength test of a sliding member according to one embodiment. [Figure 9] A schematic diagram showing the conditions for a seizure test of a sliding member according to one embodiment. [Figure 10] A schematic diagram showing the conditions for a wear test of a sliding member according to one embodiment. [Modes for carrying out the invention]

[0010] A sliding member according to one embodiment will be described below with reference to the drawings. As shown in Figure 1, the sliding member 10 comprises a base material 11 and a sliding alloy part 12. The base material 11 is formed of an Fe-based material such as steel. The sliding alloy part 12 is provided on the surface 13 of the base material 11 by welding. The sliding alloy part 12 is formed of a Cu-based alloy with Cu as the main component. The sliding alloy part 12 is formed by an assembly of multiple unit alloy parts 12A, 12B, 12C, 12D, and 12E. The sliding alloy part 12 is formed by welding. As shown in Figure 2, unit alloy parts 12A to 12E, which constitute one unit, are formed in each welding operation of the sliding alloy part 12. Then, the unit alloy parts 12A to 12E are formed sequentially in the sliding alloy part 12 as the welding operation continues. The sliding alloy part 12 is removed on the side opposite to the base material 11 by polishing or cutting, for example, up to the position of line X shown in Figure 1. As a result, Sliding alloy part 12As shown in Figure 3, a sliding surface 14 is formed on the side opposite to the base material 11, which slides against a mating material (not shown). In Figure 1, the sliding alloy part 12 is shown as an example composed of five unit alloy parts 12A to 12E for illustrative purposes. However, this is just one example, and the sliding alloy part 12 can, of course, be composed of any number of unit alloy parts, as long as there are two or more. Furthermore, an intermediate layer, for example formed by Cu plating, may be provided between the base material 11 and the sliding alloy part 12.

[0011] As shown in Figures 1 and 2, the sliding alloy portion 12 has unit interfaces 21 formed at the boundary portions between multiple unit alloy portions 12A to 12E. Specifically, the boundary portion between unit alloy portion 12A and unit alloy portion 12B is unit interface 21A. Similarly, the boundary portion between unit alloy portion 12B and unit alloy portion 12C is unit interface 21B, the boundary portion between unit alloy portion 12C and unit alloy portion 12D is unit interface 21C, and the boundary portion between unit alloy portion 12D and unit alloy portion 12E is unit interface 21D.

[0012] The sliding alloy portion 12 has a boundary region 22 within a predetermined range, as shown in Figure 4, with respect to the unit interface 21. Figure 4 shows, as an example, mainly the boundary portion between unit alloy portion 12C and unit alloy portion 12D. The boundary region 22 is set within a certain range on each side of adjacent unit alloy portions 12A to 12E, with respect to the unit interface 21. When there are multiple unit alloy portions 12A to 12E, as shown in Figure 1, unit alloy portion 12C is the range from the unit interface 21B with unit alloy portion 12B to the unit interface 21C with unit alloy portion 12D. The distance from unit interface 21B to unit interface 21C is denoted as distance L1. Similarly, the distance from unit interface 21C to unit interface 21D, which encloses unit alloy portion 12D, is denoted as distance L2. These distances L1 and L2 correspond to the weld pitch that forms the sliding alloy portion 12.

[0013] As shown in Figure 4, the boundary region 22 set at the unit interface 21C between the unit alloy portion 12C and the unit alloy portion 12D is defined as a range of 5% of the distance L1 toward the unit alloy portion 12C and a range of 5% of the distance L2 toward the unit alloy portion 12D, relative to the unit interface 21C. The region of the unit alloy portion 12C excluding the boundary region 22 is the alloy matrix region 23. In other words, in the case of the unit alloy portion 12C, the region excluding the boundary region 22 formed in the unit alloy portion 12C relative to the unit interface 21B, and the region excluding the boundary region 22 formed in the unit alloy portion 12C relative to the unit interface 21C, is the alloy matrix region 23.

[0014] The sliding alloy portion 12 contains a soft phase. The soft phase is softer than the Cu alloy matrix that constitutes the sliding alloy portion 12. In this embodiment, the soft phase is, for example, Bi or a Bi alloy. When a Bi alloy is used as the soft phase, the soft phase may also contain Se, etc. This soft phase is finely dispersed in the sliding alloy portion 12. Of these, the soft phase present in the boundary region 22 is designated as the first soft phase 31. The soft phase present in the alloy matrix region 23 is designated as the second soft phase 32. The first soft phase 31 and the second soft phase 32 have almost the same composition and are classified by whether they exist in the boundary region 22 or the alloy matrix region 23. Note that Figure 4 shows only a portion of the first soft phase 31 and the second soft phase 32 as an example for simplification.

[0015] In the observation range preset in the boundary region 22 of the sliding alloy part 12, the ratio of the total area of the first soft phase 31 contained per unit area is defined as the first area ratio S1. Further, in the alloy matrix region 23 of the sliding alloy part 12, the ratio of the total area of the second soft phase 32 contained per unit area in the preset observation range is defined as the second area ratio S2. The observation range is preferably set to a range sufficient for the first soft phase 31 or the second soft phase 32 to be included in the range. The observation range is set, for example, to a range of 300 μm × 400 μm. At this time, the first area ratio S1 and the second area ratio S2 satisfy S1 < S2. That is, in the sliding alloy part 12, the total area of the first soft phase 31 present in the boundary region 22 is smaller than that of the second soft phase 32 present in the alloy matrix region 23. When a soft phase is included in the matrix of a Cu alloy like the sliding alloy part 12, the boundary between the matrix and the soft phase has a lower strength compared to the region of the matrix where this boundary is not formed. Therefore, cracks generated in the sliding alloy part 12 due to the load applied during sliding tend to propagate along the boundary between the matrix and the soft phase. In the case of this embodiment, the first soft phase 31 contained in the boundary region 22 close to the unit interface 21 of the unit alloy part 12 has a smaller total area ratio than the second soft phase 32 contained in the alloy matrix region 23 far from the unit interface 21. Therefore, particularly in the boundary region 22, the propagation of cracks in the sliding alloy part 12 is reduced. Thus, the strength of the sliding alloy part 12 is improved, and the sliding characteristics such as fatigue resistance can be improved. Also, the crystal grain size of the sliding alloy part 12 is different between the boundary region 22 and the alloy matrix region 23. Specifically, the crystal grain size of the matrix in the boundary region 22 is smaller than that of the alloy matrix region 23 and is 1 / 10 or less. In this way, the sliding alloy part 12 has its crystal grain size refined in the boundary region 22 compared to the alloy matrix region 23.

[0016] The second soft phase 32 present in the alloy matrix region 23 has a maximum outer diameter Da such that Da ≦ 20 μm. That is, the second soft phase 32 is refined to have an outer diameter Da of 20 μm or less. The outer diameter Da of this second soft phase 32 is measured by selecting the particle of the second soft phase 32 that appears to be the largest visually from any observation cross-section extracted from the sliding alloy portion 12. For the extracted particle of the second soft phase 32 that appears to be the largest, a circumscribed circle is set. And the diameter of this circumscribed circle is taken as the outer diameter Da. Since the outer diameter Da of the second soft phase 32 is 20 μm or less, the second soft phase 32 is refined. As a result, even in the alloy matrix region 23, the propagation of cracks along the boundary between the matrix and the second soft phase 32 is reduced. Therefore, it is possible to improve sliding characteristics such as fatigue resistance. Also, due to the refinement of the second soft phase 32, the dispersibility of the second soft phase 32 in the alloy matrix region 23 is improved. Therefore, the second soft phase 32 contained in the alloy matrix region 23 of the sliding alloy portion 12 is stably supplied to the sliding portion with a mating member (not shown). Therefore, seizure in the sliding portion with the mating member can be reduced.

[0017] The sliding alloy portion 12 may further contain a third soft phase 33. The third soft phase 33 is preferably present in the boundary region 22 and formed of a specific element different from the first soft phase 31. The third soft phase 33 more preferably contains one or more elements selected from the specific elements Sn, Ni, and Al. The total area ratio of this third soft phase 33 is larger in the boundary region 22 than in the alloy matrix region 23. The specific element forming this third soft phase 33 strengthens the matrix in the sliding alloy portion 12 by solid solution. Also, this specific element forms an intermetallic compound, thereby improving the strength of the Cu-based alloy in the sliding alloy portion 12 and contributing to an improvement in wear resistance. In addition to the first soft phase 31, the second soft phase 32, and the third soft phase 33, the sliding alloy portion 12 may contain up to 6 mass% of Zn at most.

[0018] The sliding alloy portion 12 functions as a sliding layer of the sliding member 10. The total T12 of the content of the first soft phase 31 and the second soft phase 32 contained in the sliding alloy portion 12 is preferably 3 mass% to 15 mass% relative to the mass of the sliding alloy portion 12. More preferably, the total content of the first soft phase 31 and the second soft phase 32 contained in the sliding alloy portion 12 is 5 to 12 mass%. Furthermore, the content of the third soft phase 33 contained in the sliding alloy portion 12 is preferably 5 mass% to 15 mass% relative to the mass of the sliding alloy portion 12. Even more preferably, the content of the third soft phase 33 contained in the sliding alloy portion 12 is 8 to 12 mass%. The second soft phase 32 is a soft phase that reduces adhesion in the sliding portion with a mating material (not shown) and contributes to improving the seizure resistance of the sliding alloy portion 12. Therefore, by setting the total content of the first soft phase 31 and the second soft phase 32 to 3 mass% or more, it is possible to improve seizure resistance while ensuring the fatigue resistance of the sliding alloy part 12.

[0019] Furthermore, it is preferable that the total content T12 of the first soft phase 31 and the second soft phase 32 be 15 mass% or less. By making the total content T12 of the first soft phase 31 and the second soft phase 32 15 mass% or less, the content of the second soft phase 32 in the alloy matrix region 23 becomes appropriate. As a result, crack propagation in the sliding alloy part 12 can be suppressed with high precision. Consequently, it is possible to achieve both further improvement in the fatigue resistance of the sliding alloy part 12 by reducing crack propagation and improvement in the seizure resistance of the sliding member 10.

[0020] Furthermore, by making the total content T3 of the third soft phase 33 5 mass% or more, the sliding member 10 can ensure strength in the sliding alloy portion 12. Moreover, it is preferable to make the content of the third soft phase 33 15 mass% or less. In this way, by making the content of the third soft phase 33 15 mass% or less, the Cu-based alloy forming the sliding alloy portion 12 does not become excessively hard, and both strength and toughness of the sliding alloy portion 12 can be achieved.

[0021] As described above, the sliding alloy portion 12 is formed by welding. Therefore, the unit interface 21 may have a curved cross-section in the thickness direction of the sliding alloy portion 12, as shown in Figure 4. In this cross-section, the intersection point of the unit interface 21 and the base material 11 is defined as intersection point P, and the virtual tangent to the unit interface 21 at intersection point P is defined as tangent line B. The angle A that this tangent line B makes with the surface 13, which is the interface between the sliding alloy portion 12 and the base material 11, is preferably 20° ≤ A ≤ 70°. By setting this angle A to 70° or less, cracks propagating from the interface or sliding surface 14 between the base material 11 and the sliding alloy portion 12 are more likely to reach the overlapping portion of adjacent unit alloy portions 12A to 12E. In other words, taking unit interface 21C in Figure 4 as an example, cracks propagating from the interface or sliding surface 14 between the base material 11 and the sliding alloy portion 12 will hit the overlapping unit interface 21 before propagating to the opposite side. Therefore, the propagation of cracks that occur near the interface or on the sliding surface 14 through the sliding alloy part 12 to the opposite side is suppressed. Also, by setting angle A to 20° or more, the alloy matrix region 23 is more easily exposed to the sliding surface 14 after the sliding alloy part 12 has been formed. Since the alloy matrix region 23 is a Cu-based alloy, it has high seizure resistance. Therefore, seizure resistance can be improved while ensuring the fatigue resistance of the sliding alloy part 12. When the cross-section of the sliding alloy part 12 in the thickness direction is formed in a straight line, it is preferable that the angle A between this unit interface 21 and the surface 13 is 20° ≤ A ≤ 70°.

[0022] The sliding alloy part 12 may contain hard particles added from the outside to improve wear resistance. When hard particles are added, the amount of hard particles H added is preferably 5 mass% or less, and more preferably 2 mass% or less. The sliding alloy part 12 preferably has a Vickers hardness HV of 80 to 120, and more preferably 90 to 110. By making the hardness HV of the sliding alloy part 12 80 or higher, deformation of the sliding alloy part 12 due to load from a mating material (not shown) is reduced. Furthermore, in order to reduce the impact on the mating material, it is preferable that the hardness HV of the sliding alloy part 12 be 120 or less.

[0023] The sliding member 10 described above may be machined, such as by cutting or polishing, and then an overlay layer or intermediate layer may be provided on the side of the sliding alloy portion 12 opposite to the base material 11. Alternatively, the sliding member 10 can be made by welding the sliding alloy portion 12 to the outer circumference of a cylindrical or tubular shaft member 41, for example, as shown in Figure 5. This allows the sliding member 10 to be used, for example, as a rotating shaft member supporting a planetary gear.

[0024] Next, the manufacturing method of the sliding member 10 of this embodiment will be described. In this embodiment, the sliding member 10 has a sliding alloy portion 12 formed on the base material 11 by welding using laser cladding, as shown in Figure 6. When forming the sliding alloy portion 12, the laser beam 51 of the welding apparatus 50 is irradiated onto the base material 11. Upon irradiation with the laser beam 51, the powder 53 provided to the base material 11 along with the irradiation of the laser beam 51 melts. The molten powder 53 forms a molten pool 52, and solidifies upon cooling to form the sliding alloy portion 12. For example, when a shaft member 41 is used as the base material 11 as shown in Figure 5, this shaft member 41 rotates around its axis when irradiated with the laser beam 51. As a result, the sliding alloy portion 12 is formed continuously on the outer circumferential surface, which is the surface 13 of the shaft member 41. As an example, when a shaft member 41 with a diameter of 150 mm is used as the base material 11, it is preferable to set the rotation speed of the shaft member 41 to 1πrad / min to 5πrad / min. It is even more preferable to set the rotation speed of the shaft member 41 to 1.5πrad / min to 4πrad / min. In addition, it is preferable to set the axial movement speed of the shaft member 41 to 10 mm / min to 50 mm / min. By rotating the shaft member 41 and moving it axially in this way, the sliding alloy portion 12 is formed in a generally dense spiral shape on the surface 13 of the shaft member 41. As a result, the cross-section of the formed sliding alloy portion 12 is in a state where unit alloy portions 12A to 12E are assembled. In this embodiment, it is preferable that the output of the laser beam 51 be 1 kW to 10 kW. It is preferable that the specific melting rate, which is the amount of powder 53 melted relative to the output of the laser beam 51, be 0.3 kg / kW to 1 kW / kg. This specific melting rate is calculated from the output of the laser beam 51 and the supply rate of the powder 53.

[0025] The Cu-based alloy powder 53 that forms the sliding alloy portion 12 contains, for example, 5 mass% to 15 mass% of Sn, 3 mass% to 15 mass% of Bi, and the remainder being Cu and unavoidable impurities. The composition of the Cu-based alloy powder 53 can be set according to the sliding alloy portion 12 to be formed. The sliding alloy portion 12 formed on the surface of the base material 11 is preferably formed with a thickness of 2 mm or less. Furthermore, it is more preferable that the formed sliding alloy portion 12 be made to a thickness of 1 mm or less by mechanical processing such as cutting or polishing.

[0026] In this embodiment, the sliding alloy portion 12 is formed by welding using laser cladding, thereby forming a unit interface 21 at the boundary between the unit alloy portions 12A to 12E. In the boundary region 22 including this unit interface 21, the matrix of the Cu-based alloy is refined, and the total area ratio occupied by the soft phase becomes relatively smaller. As a result, crack propagation is prevented in the boundary region, and fatigue resistance is improved. Note that the method for forming the sliding alloy portion 12 is not limited to the laser cladding described above.

[0027] The following describes an embodiment of the sliding member 10 of this embodiment. Three test specimens were prepared for both the examples and comparative examples. As shown in Figure 7, the area ratio S1, area ratio S2, the maximum outer diameter Da of the second soft phase 32, the total content T12, the total content T3, and the angle A were calculated and measured for both the examples and comparative examples. The area ratio S1, area ratio S2, and the maximum outer diameter Da of the second soft phase 32 represent the maximum values ​​among the measurement results from the three test specimens. The angle A represents the average value of the measurement results from the three test specimens. The examples and comparative examples were evaluated for their "alloy hardness," and their sliding characteristics were assessed using a "fatigue strength test" based on the maximum surface pressure P1 that does not cause fatigue, a "seize test" based on the maximum surface pressure P2 that does not cause seizure, and a "wear test" based on the amount of wear Z.

[0028] Observation of the sliding alloy portion 12 was performed by cutting the sliding alloy portion 12 perpendicular to the direction of welding by laser cladding. The cross section was polished and then etched. The unit interface 21, boundary region 22, and alloy matrix region 23 were separated from the cross section. The soft phase contained in the boundary region 22 is the first soft phase 31, and the soft phase contained in the alloy matrix region 23 is the second soft phase 32.

[0029] For the boundary region 22, an observation area of ​​300 μm × 400 μm was arbitrarily set from the divided boundary region 22, and the set observation area was observed under an optical microscope at 300x magnification. The largest crystal grain was extracted from the observation area of ​​boundary region 22, and the diameter of the circumscribed circle of this extracted crystal grain was measured as the first crystal grain size Dc1. Similarly, for the alloy matrix region 23, an observation area of ​​300 μm × 400 μm was arbitrarily set from the divided alloy matrix region 23, and the set observation area was observed under an optical microscope at 100x magnification. The largest crystal grain was extracted from the alloy matrix region 23, and the diameter of the circumscribed circle of this extracted crystal grain was measured as the second crystal grain size Dc2.

[0030] The first area ratio S1 of the first soft phase 31 contained in the boundary region 22 was measured by magnifying an arbitrary 300 μm × 400 μm observation area extracted from the boundary region 22 with an optical microscope at 500x magnification. Similarly, the second area ratio S2 of the second soft phase 32 contained in the alloy matrix region 23 was measured by magnifying an arbitrary 300 μm × 400 μm observation area extracted from the alloy matrix region 23 with an optical microscope at 500x magnification. These first area ratios S1 and second area ratios S2 may also be measured mechanically, for example, by applying image processing to an image of the observation area and analyzing differences such as the color tone between the matrix and the soft phase. However, in this case, the mechanical measurement conditions for the first area ratio S1 and the second area ratio S2 should be the same.

[0031] The alloy hardness was measured using a Vickers hardness tester with a load of 5 N after polishing the cross-section of the sliding alloy part 12. The hardness HV of the sliding alloy part 12 was measured three times on the test specimen, and the average value was calculated. The fatigue strength test was performed using the conditions shown in Figure 8, with a hardness of 1 × 10⁻⁶. 7 The test was conducted in cycles. For the fatigue strength test, the surface pressure applied to the test specimen was set to an initial value of 100 MPa, and the surface pressure was increased by 10 MPa increments. If no fatigue failure occurred in the test specimen by the completion of the predetermined cycle, the fatigue strength test was considered successful at that set surface pressure. On the other hand, if fatigue failure occurred in the test specimen by the completion of the predetermined cycle, the maximum surface pressure P1 that did not cause fatigue was set to the surface pressure immediately preceding the set surface pressure.

[0032] The seizure test was performed using the conditions shown in Figure 9. In the seizure test, the surface pressure was gradually increased by 5 MPa every 10 minutes, and the maximum surface pressure at which seizure did not occur was measured. The seizure test was performed three times on the test specimen, and the average value of these measurements was calculated as the maximum surface pressure P1. The wear test was performed using the conditions shown in Figure 10. In the wear test, the vehicle was repeatedly started and stopped, with acceleration for 0.5 seconds, maintaining speed for 1.0 second, deceleration for 0.5 seconds, and stopping for 2.0 seconds. The wear test was performed by repeating this series of starts and stops for 20 hours, and the amount of thickness reduction of the sliding alloy part 12 after the test was measured. The wear test was performed three times on the test specimen, and the average value of these reductions was calculated as the wear amount Z.

[0033] In the examples and comparative examples shown in Figure 7, the sum T12 of the content of the first soft phase 31 and the second soft phase 32 is indicated as to whether or not it is in the range of 3 to 15 mass%. Examples and comparative examples where the sum T12 is in the range of 3 to 15 mass% are indicated with "○". On the other hand, examples and comparative examples where the sum T12 is not in the range of 3 to 15 mass% are indicated with "×". Specifically, the sum T12 of Example 5 is less than 3 mass%. Also, the sum T12 of Example 6 is greater than 15 mass%. Similarly, the sum T3 of the content of the third soft phase 33 is indicated as to whether or not it is in the range of 5 to 15 mass%. Examples and comparative examples where the sum T3 is in the range of 5 to 15 mass% are indicated with "○". On the other hand, examples and comparative examples where the sum T3 is not in the range of 5 to 15 mass% are indicated with "×". Specifically, the sum T3 of Example 7 is less than 5 mass%. Also, the sum T3 of Example 8 is greater than 15 mass%.

[0034] In the examples and comparative examples shown in Figure 7, the amount of hard particles added H is indicated as 5 mass% or less. Examples and comparative examples in which no hard particles were added are indicated as "-". Example 11 has an added amount H of 2 mass% or less and is indicated as "◎". Example 12 has an added amount H of 5 mass% or less and is indicated as "○". Example 13 has an added amount H exceeding 5 mass% and is indicated as "×".

[0035] For the evaluation of the examples and comparative examples, those with a maximum surface pressure P1 that does not cause fatigue in the fatigue resistance test of 120 MPa or more were evaluated as "○: Pass". Further, those with a maximum surface pressure P2 that does not cause seizure in the seizure test of 45 MPa or more, a wear amount Z of 4 μm or less in the wear test, and a maximum surface pressure P1 that does not cause fatigue of 140 MPa or more were evaluated as "◎: Excellent". On the other hand, those with a maximum surface pressure P1 that does not cause fatigue of less than 120 were evaluated as "×: Fail".

[0036] As shown in FIG. 7, in Examples 1 to 13, the relationship between the first area ratio S1 and the second area ratio S2 is S1 < S2 in all cases. In contrast, in Comparative Example 1, the relationship between the first area ratio S1 and the second area ratio S2 is S1 > S2. Examples 1 to 13 in which the relationship between the first area ratio S1 and the second area ratio S2 is S1 > S2 are improved in terms of fatigue resistance, particularly as compared with Comparative Example 1. Thus, the examples in which the first area ratio S1 in the boundary region 22 is reduced can improve the fatigue resistance, which is a sliding property.

[0037] Also, in Examples 1 to 13, the seizure resistance, fatigue resistance, and wear resistance can be controlled by setting the outer diameter Da at which the second soft phase 32 is maximum, the sum T12, the sum T3, the angle A, and the addition amount H. As a result, in Examples 1 to 13, the determination considering the seizure resistance, fatigue resistance, and wear resistance comprehensively is "◎: Excellent" or "○: Pass". In contrast, Comparative Example 1 is inferior in fatigue resistance as compared with Examples 1 to 13, and the determination is "×: Fail".

[0038] The present invention described above is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the gist thereof.

Claims

1. Substrate and A sliding alloy portion is provided on the surface of the substrate and is formed by an aggregate of multiple unit alloy parts of a Cu-based alloy mainly composed of Cu, A sliding member comprising, The aforementioned sliding alloy part is An arbitrary specific unit alloy portion selected from a plurality of the aforementioned unit alloy portions and an adjacent unit alloy portion adjacent to the aforementioned specific unit alloy portion overlap at least partially in the thickness direction. A first soft phase exists in a boundary region defined within a predetermined range based on the unit interface of the unit alloy portion, The unit alloy portion includes a second soft phase present in the region excluding the boundary region, When the total area ratio of the first soft phase contained per unit area in a predetermined observation range is defined as the first area ratio S1, and the total area ratio of the second soft phase contained per unit area in the same observation range is defined as the second area ratio S2, then S1 < S2. Sliding member.

2. The boundary region further comprises a third soft phase, which is present and originates from a specific element different from the first soft phase. The sliding member according to claim 1.

3. The second soft phase has a maximum outer diameter Da of 20 μm or less. The sliding member according to claim 1.

4. In the sliding alloy portion, the total content T12 of the first soft phase and the second soft phase is 3 to 15 mass%, and the total content T3 of the specific element constituting the third soft phase is 5 to 15 mass%. The sliding member according to claim 2.

5. The unit interface is formed with a curved cross-section in the thickness direction, When a virtual tangent is defined to the unit interface at the intersection of the unit interface and the substrate, the angle A that the tangent makes with the interface between the unit alloy portion and the substrate is: 20° ≤ A ≤ 70° The sliding member according to claim 1.

6. The first soft phase and the second soft phase are Bi or a Bi alloy. The specific element contained in the third soft phase is one or more elements selected from Sn, Ni, and Al. The sliding member according to claim 2.

7. The sliding alloy portion further contains hard particles in which the amount of added H is 5 mass% or less. The sliding member according to claim 1.

8. The Vickers hardness HV of the sliding alloy part is 80 to 120. The sliding member according to claim 1.

9. The base material is a shaft member, The sliding alloy portion is provided on the outer circumference of the shaft member. The sliding member according to claim 1.

Images