Method for manufacturing sliding member, and sliding member

Abstract

The purpose of the present disclosure is to manufacture a sliding member capable of exhibiting a wear resistance effect even when the operating temperature decreases to a low temperature range of about 300-600°C. A method according to the present disclosure is for manufacturing a sliding member that is to be operated in a high-temperature and dry environment of at least 300°C in which oxygen is present. The method involves projecting a projection material onto a substrate surface by shot peening to form, on the substrate surface, a protective lubrication layer containing a base component and a metal component derived from the projection material. The material for the projection material is selected from metal compounds and metal elements that can be changed into a metal oxide having a melting point of 300-1200°C through oxidation.

Description

Method for manufacturing a sliding member and sliding member

[0001] This disclosure relates to a method for manufacturing a sliding member and to a sliding member.

[0002] High-temperature operating machinery such as gas turbines, aircraft engines, and turbochargers generate vibrations due to rotation and fluid flow during operation. Wear occurs at points where parts come into contact with each other (sliding members) due to these vibrations.

[0003] For these reasons, in order to improve wear resistance in high-temperature environments, sliding components undergo optimization of material composition, hardening treatment, and thermal spray coating formation.

[0004] Patent Document 1 describes optimizing the composition of a heat-resistant Co-based alloy to improve work hardening characteristics. Furthermore, Patent Document 1 describes preventing wear damage to high-temperature components for gas turbines by forming a pre-hardened layer on a Co-based alloy with a novel elemental composition through shot peening treatment.

[0005] Patent Document 2 discloses a technique for improving the wear resistance of parts such as fan and compressor blades of a gas turbine engine by forming a thermal spray coating. For forming the thermal spray coating, molybdenum disulfide (MoS) is used, which has excellent wear resistance. ２ ) Thermal spray materials are used in which low-melting-point metals such as Cu and Ag are coated on the particle surface. In thermal spray coatings, MoS ２ They are present uniformly.

[0006] Japanese Patent Publication No. 2005-060727 Japanese Patent Publication No. 2007-023352

[0007] To suppress vibrations and prevent cooling air leakage, seal pins are inserted at the base of the turbine blades. A small amount of reciprocating slip occurs repeatedly between the seal pin and the turbine blade. This causes fretting wear on the seal pin.

[0008] In actual gas turbines, excessive wear of the seal pin can occur as the temperature around the seal pin decreases.

[0009] In the conventional technologies described in Patent Documents 1 and 2, the wear resistance of sliding members has been demonstrated in the high-temperature range of around 700°C. However, the wear resistance in the temperature range below 700°C has not been verified. Therefore, there is a possibility that the wear resistance over a wide temperature range is insufficient, and corresponding wear reduction measures are necessary.

[0010] This disclosure has been made in view of these circumstances and aims to provide a method for manufacturing a sliding member and a sliding member that can reduce wear in a temperature range of 700°C or less.

[0011] To solve the above problems, the manufacturing method of the sliding member and the sliding member of this disclosure employ the following means.

[0012] One aspect of the present disclosure provides a method for manufacturing a sliding member to operate in a high-temperature dry environment of 300°C or higher in the presence of oxygen, wherein a projectile is projected onto a substrate surface by shot peening to form a protective lubricating layer on the substrate surface containing metal components derived from the projectile and substrate components, and the material of the projectile is selected from metal elements or metal compounds that can become metal oxides with a melting point of 300°C to 1200°C by oxidation.

[0013] Another aspect of the present disclosure provides a sliding member for operation in a high-temperature dry environment of 300°C or higher in the presence of oxygen, comprising a base material and a protective lubricating layer covering the surface of the base material, wherein the protective lubricating layer contains elements derived from metal elements or metal compounds that can be oxidized to metal oxides with melting points from 300°C to 1200°C, and components derived from the base material.

[0014] A further aspect of the present disclosure provides a sliding member for operation in a high-temperature dry environment of 300°C or higher in the presence of oxygen, comprising a base material and a protective lubricating oxide layer covering the surface of the base material, wherein the protective lubricating oxide layer comprises a metal oxide having a melting point of 300°C to 1200°C and components derived from the base material.

[0015] According to the above disclosure, it is possible to manufacture a sliding member that can exhibit wear resistance even when the operating temperature drops to a temperature range of 700°C or less.

[0016] This is a schematic cross-sectional view of a sliding member. This is a schematic view of a gas turbine blade. This is a schematic cross-sectional view illustrating the sliding between the seal pin and the seal pin groove. This is a cross-sectional photograph of a test specimen in which Sn was used to form the protective lubrication layer. MoS ２ This is a cross-sectional photograph of a test specimen using the following method: A graph showing the results of hardness measurements for each specimen. A graph showing the results of a fretting abrasion test (temperature 300°C) for a specimen using a Ni-based heat-resistant alloy as the base material. A graph showing the results of a fretting abrasion test (temperature 300°C) for a specimen using a Co-based heat-resistant alloy as the base material. Cross-sectional photographs of each specimen taken with a scanning electron microscope. A graph showing the results of elemental analysis of the surface layer of the specimen after sliding.

[0017] A method for manufacturing a sliding member and an embodiment of the sliding member according to this disclosure will be described below with reference to the drawings.

[0018] [Sliding Member] Figure 1 shows a schematic cross-sectional view of the sliding member. The sliding member 1 comprises a base material 2 and a protective lubricating layer 3 that covers the surface of the base material (sliding surface).

[0019] The material of base material 2 may be a nickel-based alloy, a cobalt-based alloy, or stainless steel, etc.

[0020] The average hardness of the substrate surface is preferably 11.1 times or more higher than the average hardness of the interior of the substrate. "Surface" refers to the region from the outermost surface up to a maximum depth of 500 μm. "Average hardness" refers to the average value of 5 to 10 hardness points on the substrate surface, measured by pressing an indenter into the cross-section of the substrate.

[0021] The protective lubrication layer 3 contains components (metal elements) derived from the base material 2 and components derived from the abrasive material used to form the protective lubrication layer 3. The abrasive material contains metal elements or metal compounds. Elements derived from metal elements or metal compounds can be oxidized to metal oxides with melting points ranging from 300°C to 1200°C. The melting point of the metal oxide is higher than the upper limit of the operating temperature of the sliding member 1.

[0022] Metallic elements or metal compounds include Sn, Bi, Mo, Mn, and MoS ２It may be any of them. The metal oxide formed by oxidizing the metal element or metal compound may be, for example, MnO ２ (melting point 535 ° C), MoO ３ (melting point 795 ° C), Bi ２ O ３ (melting point 820 ° C), Mn ２ O ３ (melting point 1080 ° C), SnO ２ (melting point 1127 ° C). Note that MnO ２ (melting point 535 ° C) changes to Mn ２ O ３ (melting point 1080 ° C) around 590 ° C.

[0023] The sliding member 1 is suitable for use in a high-temperature dry environment of 300 ° C or higher. Oxygen exists in the high-temperature dry environment. The "dry environment" is an environment in which the sliding member operates without the intervention of a fluid such as lubricating oil.

[0024] When the sliding member 1 operates in a high-temperature dry environment, the metal element or metal compound contained in the protective lubricating layer 3 is oxidized by the oxygen present in the surroundings. As a result, the protective lubricating layer 3 becomes a protective lubricating oxide layer.

[0025] The sliding member 1 may be configured to be used in a sliding part of a gas turbine, an aeroengine, or a turbocharger. The upper limit of the operating temperature of the sliding part of a gas turbine, an aeroengine, or a turbocharger is 300 ° C or higher.

[0026] As a specific example, a case where the sliding member 1 according to the present embodiment is applied to a seal pin that is contact-arranged between adjacent gas turbine moving blades will be described.

[0027] FIG. 2 shows a schematic view of a gas turbine moving blade. The gas turbine moving blade 10 includes a blade part 11, a platform 12, and a blade root part 13. The blade root part 13 is embedded in a rotor (not shown) of the gas turbine moving blade 10. The platform 12 is integrally formed with the blade root part 13.

[0028] The blade section 11 is provided to extend along the radial direction of the rotor and has a base end 14 fixed to the platform 12 and a tip end 15 located on the opposite side from the base end 14 in the blade height direction (radial direction of the rotor).

[0029] The wing portion 11 has a leading edge 16 and a trailing edge 17 from the base 14 to the tip 15. The wing surface of the wing portion 11 includes a pressure surface (ventral surface, not shown) and a negative pressure surface (back surface) 18 that extend along the wing height direction (radial direction) between the base 14 and the tip 15.

[0030] The platform 12 has a groove 19 that is recessed from the side facing the trailing edge 17 toward the leading edge 16 and extends in the circumferential direction of the rotor. The platform 12 has a seal pin groove 20 in which a seal pin (not shown) is positioned to seal the gap between the platform 12 of other adjacent rotor blades in the circumferential direction. In Figure 2, the seal pin groove 20 is formed on the end face 22 on the negative pressure side (back side) of the platform 12.

[0031] Figure 3 is a schematic cross-sectional view illustrating the sliding motion between the seal pin 21 and the seal pin groove 20. The seal pin 21 is a cylindrical member. The seal pin 21 is in contact with the seal pin groove 20, and minute reciprocating sliding motion occurs repeatedly between the seal pin 21 and the seal pin groove 20.

[0032] The seal pin 21, positioned between adjacent rotor blades and in contact with them, functions as a sealing structure that suppresses the flow of gas between the space on the blade root side 13 and the space on the blade side 11. This prevents the leakage of combustion gases. In addition, the seal pin 21 functions as a damper pin that dampens the vibration of the rotor blade through the frictional force between the seal pin 21 and the seal pin groove 20.

[0033] No fluid, such as lubricating oil, is interposed between the seal pin 21 and the seal pin groove 20. The area around the seal pin 21 is a high-temperature gas atmosphere containing oxygen.

[0034] In a high-temperature dry environment of 300°C or higher where oxygen is present, when the seal pin 21 is operated, the metal elements or elements derived from metal compounds contained in the protective lubrication layer 3 are oxidized by the surrounding oxygen. As a result of this oxide derived from the protective lubrication layer 3 mixing with oxide derived from the substrate, a protective lubrication oxide layer 4 is formed on the sliding surface.

[0035] [Method for Manufacturing a Sliding Member] In the method for manufacturing a sliding member according to this embodiment, a projectile is projected onto the substrate surface (the sliding surface of the sliding member) by shot peening to form a protective lubricating layer on the substrate surface. The substrate surface may be pre-treated before forming the protective lubricating layer.

[0036] (Formation of protective lubrication layer) The material of the abrasive is selected from metal elements or metal compounds that can be oxidized to form metal oxides with melting points of 300°C to 1200°C (can be sources of metal oxides). The materials of the abrasive are Sn, Bi, Mo, Mn and MoS ２ A selection can be made from the group consisting of the following.

[0037] The material of the abrasive material should be selected such that the melting point of the metal oxide formed when the material is oxidized does not fall below the upper limit of the operating temperature of the sliding member. For example, if the upper limit of the operating temperature (ambient temperature) of the sliding member is 300°C, the abrasive material should be Sn, Bi, Mo, Mn, and MoS ２ It can be selected from the following. For example, if the upper limit of the operating temperature (usage environment temperature) of the sliding member is 600°C, the material of the projection material may be Sn, Bi, Mo, and MoS ２ It can be selected from the following. If the upper limit of the operating temperature (usage environment temperature) of the sliding member is 900°C, it is preferable to use Mn or Sn as the material for the projection material.

[0038] The spray pressure of the abrasive material is between 0.6 MPa and 2.0 MPa. The sprayed abrasive material adheres to the substrate surface and forms a protective coating (protective lubricating layer) that covers the substrate surface.

[0039] (Pretreatment) Pretreatment is performed by shot peening. The hard particles have a hardness equal to or greater than that of the base material. The hard particles may be high-speed tool steel or the like. The average particle size of the hard particles may be 0.05 mm or more and 0.35 mm or less.

[0040] Hard particles are sprayed at a spray pressure of 0.1 MPa to 0.5 MPa and made to collide with the substrate surface. The spraying can be carried out using an existing shot peening apparatus. The hardness of the substrate surface can be improved by spraying (colliding with) the hard particles. In the pretreatment, it is preferable to increase the average hardness of the substrate surface by 1.1 times or more than the average hardness of the substrate material itself.

[0041] [Example] (Preparation of test specimens) The substrate surface was pretreated according to the above embodiment, and then a protective lubricating layer was formed on the pretreated substrate surface by shot peening to obtain test specimens.

[0042] Ni-based heat-resistant alloy (Inconel-X750) and Co-based heat-resistant alloy were used as the base materials.

[0043] The pretreatment conditions were the same for all test specimens.

[0044] The projection material for forming the protective lubrication layer is Sn or MoS ２ I used it.

[0045] The Ni-based heat-resistant alloy and Co-based heat-resistant alloy used as the base material, and the MoS used as the projection material. ２ The color is different from that of Sn. Visual confirmation confirmed the formation of a protective lubricating layer on the substrate surface.

[0046] (Composition of protective lubrication layer) Cross-sectional samples of test specimens using Inconel-X750 (Ni-based heat-resistant alloy) as the substrate were prepared. Elemental analysis was performed on each cross-sectional sample using a scanning electron microscope.

[0047] Figure 4 shows the elemental analysis results of a test specimen using Sn as the projection material. (a) is a secondary electron image, (b) is an analysis image of Ni, (c) is an analysis image of Sn, and (d) is an analysis image of O. In the test specimen using Sn as the projection material, the presence of Ni, Sn, and O was confirmed on the substrate surface. According to Figure 4(c), the concentration of Sn did not change in a gradient from the outermost surface to the interior of the substrate (depth direction), but rather a variation in density was observed in the in-plane direction of the substrate surface. From this, it is thought that Sn did not diffuse into the substrate, but rather was stirred and mixed with Ni during the shot peening process.

[0048] Figure 5 shows MoS as the projection material.２ This figure shows the elemental analysis results of a test specimen using [a]. (a) is a secondary electron image, (b) is an analysis image of Ni, (c) is an analysis image of Mo, (d) is an analysis image of S, and (e) is an analysis image of O. MoS [a] is projected onto the material. ２ In the test specimens using this method, the presence of Ni, Mo, S, and O on the substrate surface was confirmed. As shown in Figure 5, Mo and S are attached to the surface layer of the substrate (Ni).

[0049] According to Figures 4 and 5, the components (Sn, Mo, or S) contained in the projection material were all distributed near the surface of the substrate.

[0050] (Hardness) Cross-sectional samples were prepared for each test specimen. For each cross-sectional sample, hardness was measured at multiple locations at different depths from the surface. The measurements were performed according to the method compliant with JIS Z2244:2009. The results are shown in Figure 6. "Hardening depth" is the distance from the surface in the depth direction until a hardness equivalent to that of the untreated substrate is obtained. "Average hardness" is the average of the hardness measured at multiple locations from the surface to the hardening depth.

[0051] As shown in Figure 6, regardless of the substrate material or the projection material of the protective lubrication layer, the surface hardness and average hardness of the treated surface (protective lubrication layer) of the test specimen (substrate) improved compared to the untreated surface. Pretreatment by shot peening increased the average hardness of the substrate surface by 1.1 to 1.6 times compared to the untreated substrate surface. The hardening depth for each test specimen ranged from 0.04 mm to 0.05 mm.

[0052] (Fretting Abrasion Test) A fretting abrasion test was conducted on each test specimen. For comparison, the same fretting abrasion test was also conducted on an untreated substrate. The test conditions were as follows:

[0053] Countering material: Ni-based heat-resistant alloy Temperature: 300°C to 600°C Surface pressure: 80 MPa to 700 MPa Frequency: 50 Hz to 500 Hz Amplitude: 0.03 mm to 0.5 mm

[0054] Figure 7 shows the results of a fretting abrasion test (at 300°C) on a test specimen using a Ni-based heat-resistant alloy as the base material. Figure 8 shows the results of a fretting abrasion test (at 300°C) on a test specimen using a Co-based heat-resistant alloy as the base material. In Figures 7 and 8, the vertical axis represents the percentage change in abrasion amount compared to the untreated sample.

[0055] According to Figure 7, the lower the melting point of the metal oxide interposed on the sliding surface, the lower the amount of wear.

[0056] Compared to untreated substrates that had not undergone pretreatment or protective lubrication layer formation, the amount of wear was significantly reduced in the test specimens that had undergone pretreatment and protective lubrication layer formation. The substrate was a Ni-based heat-resistant alloy and MoS was used as the abrasive material. ２ The test specimens using this method showed an 80% reduction in wear compared to the untreated substrate (see Figure 7). The substrate was a Co-based heat-resistant alloy and MoS was used as the abrasive material. ２ The test specimens treated with this method showed an 88% reduction in wear compared to the untreated substrate (see Figure 8).

[0057] These results suggest that the sliding member according to the above embodiment can achieve a wear reduction effect regardless of the material of the base material (material to be treated). The sliding member according to the above embodiment can be applied to gas turbine combined cycle power plants (GTCC), aircraft engines, turbochargers, etc., which use different materials.

[0058] (Protective Lubricating Oxide Layer) Cross-sectional samples were prepared from the test specimens after the fretting wear test. Each cross-sectional sample was subjected to a scanning electron microscope to observe the cross-section and perform elemental analysis.

[0059] Figure 9 shows cross-sectional images taken with a scanning electron microscope. Figure 9(a) is a cross-sectional image of an untreated substrate (Ni-based heat-resistant alloy or Co-based heat-resistant alloy) after sliding. Figure 9(b) shows the Ni-based heat-resistant alloy or Co-based heat-resistant alloy after pretreatment and then MoS ２ This is a cross-sectional photograph of a test specimen after sliding, in which a protective lubrication layer was formed by projecting a protective lubrication layer.

[0060] Regardless of the substrate material, pretreatment, and the presence or absence of a protective lubricating layer, the presence of a separate layer (surface layer) distinct from the substrate was confirmed on the sliding surface after the fretting wear test.

[0061] In Figures 7 and 8, numerous cracks were observed on the sliding surface of the untreated substrate (Ni-based heat-resistant alloy or Co-based heat-resistant alloy) (a), which showed high wear, regardless of the type of substrate. From this, it can be said that the surface layer of (a) is brittle.

[0062] On the other hand, MoS showed low wear after pretreatment, as seen in Figures 7 and 8. ２ On the sliding surfaces of the test specimens onto which the projection was applied, a dense surface layer free of cracks was observed, regardless of the type of substrate.

[0063] Figure 10 shows the elemental analysis results of the surface layer of the test specimen after sliding. In Figure 10, (a) is the substrate (Ni-based heat-resistant alloy: Inconel-X750), (b) is the test specimen after Sn projection following pretreatment, and (c) is after MoS ２ This is the composition of the surface layer of the sliding surface of the test specimen onto which the projection was applied.

[0064] In all of the sliding surfaces shown in Figures 10(a) to (c), the surface layer contained a large amount of Ni, a metal element derived from the substrate, and oxygen. From this, it can be said that the surface layer is a Ni-dominant oxide layer. The oxide layer (protective lubricating oxide layer) of the test specimens in (b) and (c) contained metal elements (Sn, Mo, or S) derived from the abrasive material. On the other hand, Sn, Mo, or S were not detected in the oxide layer of the sliding surface of the untreated substrate in (a).

[0065] From the results in Figures 9 to 10 above, a brittle Ni oxide layer was formed on the sliding surface of the untreated substrate due to friction, whereas pretreatment and Sn or MoS ２ On the sliding surface of the substrate onto which the coating was projected (after sliding), it was confirmed that a dense Ni oxide layer containing oxides derived from the protective lubricant layer was formed by friction.

[0066] Metal elements derived from the abrasive material can oxidize to metal oxides with melting points ranging from 300°C to 1200°C. It is believed that the formation of such low-melting-point metal oxides on the sliding surface acts as a binder, bonding the metal oxides derived from the base material (substrate), thereby promoting the formation of a dense protective lubricating oxide layer even under low-temperature conditions of around 300°C.

[0067] Figures 7 and 8 above show that the amount of wear on the pre-treated and protective lubrication layer-formed test specimens was significantly reduced compared to the untreated substrate. This suggests that the protective lubrication oxide layer, which contains oxides derived from the protective lubrication layer, exhibits a wear reduction effect at temperatures below 700°C.

[0068] <Note> The manufacturing method and the sliding member described in the embodiments above can be understood, for example, as follows.

[0069] A method for manufacturing a sliding member according to a first aspect of this disclosure is a method for manufacturing a sliding member to be operated in a high-temperature dry environment of 300°C or higher in the presence of oxygen, wherein a projectile is projected onto a substrate surface by shot peening to form a protective lubricating layer on the substrate surface containing metal components derived from the projectile and substrate components, and the material of the projectile is selected from metal elements or metal compounds that can become metal oxides with a melting point of 300°C to 1200°C by oxidation.

[0070] When sliding members are operated in a high-temperature dry environment of 300°C or higher where oxygen is present, the metal components contained in the sliding members are oxidized.

[0071] By using a metal element or metal compound that can be oxidized to form a metal oxide with a melting point of 300°C to 1200°C as the material for the projection agent, a low-melting-point metal oxide with a melting point of 300°C to 1200°C is generated on the surface of the sliding member after operation. As a result, the protective lubrication layer becomes a dense protective lubrication oxide layer containing oxides originating from the protective lubrication layer.

[0072] Low-melting-point metal oxides act as binders, binding the metal oxides oxidized from the base material. By including metal components that can serve as sources of low-melting-point metal oxides in the protective lubricant layer, the formation of a dense protective lubricant oxide layer can be promoted even at low temperatures of 300°C. Such a protective lubricant oxide layer can exhibit wear resistance in the operating temperature range of 700°C or below.

[0073] In the method for manufacturing a sliding member according to a second aspect of the present disclosure, in the first aspect, the material of the projection material is Sn, Bi, Mo, Mn and MoS ２ It is selected from the group consisting of the following.

[0074] Sn, Bi, Mo, Mn, and MoS ２ The oxides are, respectively, SnO ２ (Melting point 1127°C), Bi ２ O ３ (Melting point 820°C), MoO ３ (Melting point 795°C), MnO ２ (Melting point 535°C), Mn ２ O ３ (Its melting point is 1080°C.)

[0075] In a method for manufacturing a sliding member according to a third aspect of the present disclosure, in the first or second aspect, the material of the projection material is selected such that the melting point of the metal oxide does not fall below the upper limit of the operating temperature of the sliding member.

[0076] Preferably, the melting point of the metal oxides (metal oxides) derived from the abrasive material contained in the protective lubricating oxide layer does not fall below the upper limit of the operating temperature of the sliding member. Preferably, the melting point of the metal oxides is close to the upper limit of the operating temperature of the sliding member.

[0077] In a method for manufacturing a sliding member according to a fourth aspect of the present disclosure, in any of the first to third aspects, hard particles harder than the substrate are used, and before forming the protective lubricating layer, the hard particles are projected onto the substrate surface by shot peening to increase the hardness of the substrate surface.

[0078] By increasing the hardness of the substrate surface before forming a protective lubricating layer, wear can be reduced.

[0079] A sliding member according to a fifth aspect of the present disclosure is a sliding member for operation in a high-temperature dry environment of 300°C or higher in the presence of oxygen, comprising a base material and a protective lubricating layer covering the surface of the base material, wherein the protective lubricating layer contains elements derived from metal elements or metal compounds that can be oxidized to metal oxides with melting points from 300°C to 1200°C, and elements derived from the base material.

[0080] In the sliding member according to the sixth aspect of this disclosure, in the fifth aspect, the metal element or metal compound is Sn, Bi, Mo, Mn and MoS ２ It is one of the following:

[0081] In the sliding member according to the seventh aspect of this disclosure, in the fifth or sixth aspect, the average hardness of the substrate surface is 1.1 or higher than the average hardness of the substrate material.

[0082] A sliding member according to an eighth aspect of the present disclosure is a sliding member for operation in a high-temperature dry environment of 300°C or higher in the presence of oxygen, comprising a base material and a protective lubricating oxide layer covering the surface of the base material, wherein the protective lubricating oxide layer contains metal oxides having a melting point of 300°C to 1200°C and oxides of elements derived from the base material.

[0083] In the sliding member according to the ninth aspect of this disclosure, in the eighth aspect, the metal oxide is SnO ２ , Bi ２ O ３ , MoO ３ , MnO ２ and Mn ２ O ３ It is one of the following:

[0084] 1. Sliding member 2. Base material 3. Protective lubrication layer 4. Protective lubrication oxide layer 10. Gas turbine blade 11. Blade section 12. Platform 13. Blade root 14. Base end 15. Tip 16. Leading edge 17. Trailing edge 18. Negative pressure surface (back side) 19. Groove 20. Seal pin groove 21. Seal pin 22. End face on negative pressure surface side (back side)

Claims

1. A method for manufacturing a sliding member to operate in a high-temperature dry environment of 300°C or higher in the presence of oxygen, comprising: projecting a projectile onto a substrate surface by shot peening to form a protective lubricating layer on the substrate surface containing components of the projectile and components of the substrate; wherein the material of the projectile is selected from metal elements or metal compounds that can become metal oxides with a melting point of 300°C to 1200°C upon oxidation.

2. The material of the projection material is Sn, Bi, Mo, Mn, and MoS ２ A method for manufacturing a sliding member according to claim 1, selected from the group consisting of the following.

3. The method for manufacturing a sliding member according to claim 1, wherein the material of the projection material is selected such that the melting point of the metal oxide does not fall below the upper limit of the operating temperature of the sliding member.

4. A method for manufacturing a sliding member according to claim 1, wherein hard particles harder than the substrate are used, and the hard particles are projected onto the substrate surface by shot peening before forming the protective lubricating layer, thereby increasing the hardness of the substrate surface.

5. A sliding member for operation in a high-temperature dry environment of 300°C or higher in the presence of oxygen, comprising a base material and a protective lubricating layer covering the surface of the base material, wherein the protective lubricating layer contains elements derived from metal elements or metal compounds that can be oxidized to become metal oxides with melting points of 300°C to 1200°C, and elements derived from the base material.

6. The metal element or metal compound is Sn, Bi, Mo, Mn, and MoS ２ The sliding member according to claim 5, which is any of the above.

7. The sliding member according to claim 5, wherein the average hardness of the substrate surface is 1.1 or higher than the average hardness of the material of the substrate.

8. A sliding member for operation in a high-temperature dry environment of 300°C or higher in the presence of oxygen, comprising a base material and a protective lubricating oxide layer covering the surface of the base material, wherein the protective lubricating oxide layer contains metal oxides with melting points from 300°C to 1200°C and oxides of elements derived from the base material.

9. The metal oxide is SnO ２ , Bi ２ O ３ , MoO ３ , MnO ２ and Mn ２ O ３ The sliding member according to claim 8, which is any one of them.

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