JP4976804B2 - Nitriding member, friction member and vibration wave driving device - Google Patents

Description

The present invention, nitride members obtained by nitriding austenitic stainless steel, and a friction member and the vibration wave driving apparatus using the same using the nitride member.

  Conventionally, after stainless steel is ion-nitrided (also referred to as plasma nitriding), its surface is polished to a mirror state and used as a glass mold (see, for example, Patent Document 1). This mold is excellent in hardness, heat resistance, releasability, and mirror finish.

Further, there is a report that if austenitic stainless steel is ion nitrided at a temperature lower than the normal nitriding temperature of 673 K, a phase with high corrosion resistance is generated on the nitrided surface layer (see, for example, Non-Patent Document 1).
Japanese Patent No. 3011574 Ichii, Fujimura, Takase “Surface structure and corrosion resistance and hardness of ion-nitrided 18-8 stainless steel” Heat treatment 1985, Vol.

  The above-mentioned conventional mold for glass is used in a limited atmosphere such as in a vacuum or an inert gas, and in such a case, no particular problem occurs. However, corrosion (rust, that is, wet corrosion) may occur in an application where a nitrided member made of stainless steel that has been subjected to nitriding treatment is used in an environment where moisture exists as in normal air. Further, if the humidity is present in an atmosphere such as in the atmosphere and the temperature is slightly raised from room temperature, the surface of the nitrided member may be oxidized (dry) and the surface may be roughened. As this further proceeds, an oxide film having a certain thickness is formed on the surface of the nitriding member, and this oxide film may be separated from the surface by an external force.

  These phenomena are attributed to the precipitation of chromium nitride (stable phase) by combining nitrogen atoms that have diffused into the base metal with chromium originally dissolved in iron. It is considered. In other words, in the vicinity of the chromium nitride, chromium necessary for nitride formation diffuses to the nitride side, the chromium content in the solid solution state decreases, and a chromium passive film is hardly formed. This means that the chromium nitride is so-called sensitized to the corrosive environment. That is, nitriding significantly lowers the inherent corrosion resistance of stainless steel.

  Therefore, as described above, attempts have been made to nitride austenitic stainless steel at a low temperature of 673K or lower. It has been reported that the phase constituting the nitride layer generated by nitriding treatment at such a relatively low temperature has high corrosion resistance unlike the phase generated at high temperature.

  However, in the nitriding treatment at a low temperature, the diffusion rate of nitrogen atoms is remarkably reduced, so that a thick nitride layer cannot be formed. When the nitride layer is thin, the nitride layer is easily broken or peeled off by an external force pressing the surface. Also, when the surface is finished smoothly by polishing or the like like a mold material, a thick nitride layer is required because of the need for machining allowance.

  In order to obtain a thick nitride layer, it may be possible to perform a nitriding process at a low temperature for a long time, but this is not practical. This is because a nitride layer is formed by diffusion of nitrogen atoms, and it takes a very long time to form a nitride layer having the same thickness even if the nitriding temperature is slightly lowered. It is.

  In addition, a brittle layer that hardly corrodes may be formed near the surface of the nitride layer under a certain nitriding condition. However, the white layer is extremely thin, and is removed when the surface is polished, and thus is unsuitable for applications where such a surface needs to be polished.

  Thus, with the conventional method, it is very difficult to obtain a thick nitride layer with high corrosion resistance.

  An object of the present invention is to provide a nitrided member in which a thick nitrided layer having excellent corrosion resistance is formed, and to provide a vibration wave driving device in which the nitrided member is used as a friction member.

In order to achieve the above object, the nitriding member of the present invention has Ti of 0.8 to 3.0 wt%, Ni of 5.0 to 15.0 wt%, Cr of 15.0 to 25.0 wt% , Austenitic stainless steel containing 0 to 0.209% by weight of S, having a nitride layer thicker than 30 μm on the surface, the nitride layer having a Vickers hardness of 1080 Hv or more at a position of 20 μm from the surface And

In order to achieve the above-mentioned object, the friction member of the present invention has Ti of 0.8 to 3.0% by weight, Ni of 5.0 to 15.0% by weight, Cr of 15.0 to 25.0% by weight , Austenitic stainless steel containing 0 to 0.209% by weight of S, having a nitride layer thicker than 30 μm on the surface, the nitride layer having a Vickers hardness of 1080 Hv or more at a position of 20 μm from the surface And

In order to achieve the above object, a vibration wave driving device of the present invention includes a vibrator excited by vibration by an electro-mechanical energy conversion element, a moving element driven by the vibration excited by the vibrator, and the vibration. And at least one of the child and the moving member, and a friction member provided so as to be in contact with the other, the friction member comprising Ti of 0.8 to 3.0 wt% and Ni of 5.0 to 15 An austenitic stainless steel containing 0.0 wt%, Cr 15.0 to 25.0 wt% , and S 0 to 0.209 wt% , and having a nitride layer thicker than 30 μm on the surface, Vickers hardness is 1080 Hv or more at a position of 20 μm from the surface.

  According to the present invention, a nitrided member having good workability, excellent corrosion resistance, and a thicker nitrided layer can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the configuration of a rod-type ultrasonic motor that is a vibration wave driving device to which a nitriding member according to an embodiment of the present invention is applied as a friction member will be described with reference to FIGS. 18 and 19. FIG. 18 is a longitudinal sectional view showing the configuration of the rod-type ultrasonic motor. FIG. 19A is a diagram schematically showing the vibration mode of the rod-type ultrasonic motor of FIG. 18, and FIG. 19B is a diagram schematically showing the vibration mode.

  As shown in FIG. 18, the rod-type ultrasonic motor includes an elastic body 1, an elastic body 2, a laminated piezoelectric element 3 that is an electro-mechanical energy conversion element, a rotor 7, and a gear 8. The elastic bodies 1 and 2, the laminated piezoelectric element 3, the rotor 7 and the gear 8 are inserted through the shaft 4. At both ends of the shaft 4, thread portions that are screwed into the nuts 5 and 11 are formed, and at the intermediate portion, a flange portion 4 a is formed. The laminated piezoelectric element 3 is disposed between the elastic bodies 1 and 2, and the elastic bodies 1 and 2 and the laminated piezoelectric element 3 are screwed into one end of the shaft 4 and the flange portion of the shaft 4. It is pinched and fixed so that predetermined clamping force is provided between 4a. A ring-shaped friction member 6 having wear resistance is provided at an end of the elastic body 1. Details of the friction member 6 will be described later.

  The rotor 7 is arranged so that one end surface thereof is in contact with the friction member 6 provided on the elastic body 1. One end face of the rotor 7 is formed so as to have a small contact width with the friction member 6 and an appropriate spring property. On the other end face of the rotor 7, a recess is formed that can be engaged with the protrusion of the gear 8 for transmitting the motor output to the outside. The gear 8 is rotatably fitted to the lower portion of the flange 10 for attaching the ultrasonic motor, and is fixed by the flange 10 so as not to move in the thrust direction of the shaft 4. A pressure spring 15 for pressing the rotor 7 against the friction member 6 is provided between the gear 8 and the rotor 7.

  Here, as shown in FIG. 19A, the elastic body 1, the elastic body 2, the laminated piezoelectric element 3, the shaft 4, the friction member 6 and the nut 5 constitute a rod-shaped vibrator. In the laminated piezoelectric element 3, electrodes (not shown) are grouped into two electrode groups, and AC electric fields having different phases are applied to the respective electrode groups from a power source (not shown). When the AC electric field is applied to the electrode group of the laminated piezoelectric element 3, two bending vibrations orthogonal to each other are excited in the vibrator.

  One of the excited bending vibrations is a vibration in a direction parallel to the paper surface shown in FIG. The other bending vibration is a vibration in a direction perpendicular to the paper surface. By adjusting the phase of the applied AC electric field, a time phase difference of π / 2 (rad) can be given between the two bending vibrations. As a result, the bending vibration of the vibrator It rotates around the child axis (around the axis of the shaft 4). As a result, an elliptical motion is generated on the end face of the elastic body 1 that contacts the rotor 7, and the rotor 7 pressed by the friction member 6 is frictionally driven, so that the rotor 7, the gear 8, and the pressure spring 15 rotate together. To do. Then, the rotational driving force of the gear 8 is transmitted to an external gear (not shown) as a motor output.

  As a vibration wave driving device to which the nitriding member according to the embodiment of the present invention is applied as a friction member, there is, for example, an annular ultrasonic motor in addition to the rod ultrasonic motor. The annular ultrasonic motor will be described with reference to FIG. FIG. 20A is a longitudinal sectional view showing the configuration of an annular ultrasonic motor, and FIG. 20B is a perspective view of the vibrator.

  The annular ultrasonic motor includes a housing 30 as shown in FIG. An output shaft 28 is rotatably supported by the housing 30 via a plurality of bearings 31. The output shaft 28 is connected to a drive mechanism of an operation device such as various devices and equipment using the ultrasonic motor as a drive source via a gear (not shown).

  An annular elastic body 21 is fixed to the housing 30 with screws 32. The annular elastic body 21 is arranged coaxially with the output shaft 28. On one surface of the elastic body 21, a friction member 26 that comes into contact with the annular moving body 27 is provided. An annular piezoelectric element 23 as an electro-mechanical energy conversion element is attached to the other surface of the elastic body 21.

  Specifically, the elastic body 21 is manufactured in an annular shape by molding such as cutting of metal material or powder sintering. As shown in FIG. 20B, a plurality of comb-like protrusions protruding in the axial direction are formed on one surface (front surface) of the elastic body 21, and the upper surface of the plurality of protrusions has a frictional surface. The member 26 is bonded. A plurality of electrodes 22 are provided on the piezoelectric element 23 attached to the other surface (back surface) of the elastic body 21. The elastic body 21, the piezoelectric element 23, and the friction member 26 constitute a vibrator.

  Up to now, the friction member has been described as being configured as a separate member from the elastic body. However, by selecting stainless steel as the elastic member and subjecting it directly to nitriding, the friction part is integrated with the elastic body. You can also. When the friction member and the elastic body are integrated, the manufacturing process can be shortened without worrying that the friction portion will fall off the elastic member. In particular, in a vibrator having a configuration in which a friction member is bonded to the upper surface portion of the comb-shaped projection, the number of friction members is required for the number of comb teeth. Is obtained.

  The moving body 27 is arranged so that one surface thereof faces the friction member 26 and is coaxial with the output shaft 28. The moving body 27 is supported by a pressure spring member 35 fixed to the output shaft 28. The pressure spring member 35 generates a spring force that causes the moving body 27 to be in pressure contact with the friction member 26.

  Here, when an AC electric field is applied to the electrode of the piezoelectric element 23, the vibrator is excited, and the moving body 27 that is in pressure contact with the friction member 26 is rotationally driven integrally with the output shaft 28. As a result, the motor output is transmitted to an external drive mechanism.

  In the present embodiment, rod-type and annular-type ultrasonic motors are exemplified as the ultrasonic motor to which the nitriding member is applied as the friction member. However, the nitriding member according to the present invention is not limited to these, and various types of ultrasonic motors configured according to the shape of the vibrating body, the order of vibration to be excited, the form of vibration, etc. It is thought that it can be applied as a friction member.

  Next, the nitriding member forming the friction member of the ultrasonic motor described above will be described with reference to FIGS. 1 to 3 are micrographs of cross sections of friction members made of nitride members according to the first embodiment, the second embodiment, and the third embodiment of the present invention, respectively. is there. FIG. 4 is a view showing a micrograph of a cross section of a friction member made of a nitride member of the first manufacturing material with the Ti content outside the scope of the present invention. FIG. 5 is a view showing a micrograph of a cross-section of a friction member made of a nitride member of the second production material with a Ti content outside the scope of the present invention. 6-11 is a figure which shows the microscope picture of the cross section of the friction member which consists of each commercially available JIS standard stainless steel, respectively. FIG. 12 is an electron micrograph of the nitride layer portion of the second manufacturing material. FIG. 13 is a diagram showing a mapping image of N in the nitride layer portion of FIG. FIG. 14 is a diagram showing a mapping image of Ti in the nitride layer portion of FIG. FIG. 15 is a graph showing the thickness of the nitrided layer when nitriding is performed at each temperature. FIG. 16 is a graph showing the hardness of the nitrided layer when nitriding is performed at each temperature. FIG. 17 is a perspective view showing the outer shape of a friction member made of a nitride member according to one embodiment of the present invention. Here, the friction member 6 shown in FIG. 17 can be used as the annular friction member 6 used in the rod-type ultrasonic motor shown in FIG. 18, and this friction member 6 is taken as an example in the present invention. The nitriding member according to the embodiment will be described.

  Here, the case where the said friction member is formed from 11 types of materials represented by following Table 1 is demonstrated. These eleven kinds of materials include three kinds of austenitic stainless steel materials constituting the first, second and third embodiments of the present invention, and two kinds of steel materials of the first and second production materials, respectively. 6 types of JIS standard stainless steel materials. The composition of these materials is expressed in weight percent.

  The three types of austenitic stainless steel materials constituting the first to third embodiments and the two types of stainless steel materials of the first and second production materials are 50 kg of steel produced in a vacuum induction furnace. It was prepared as a lump. Each ingot is held at a temperature of 1473 K for 2 hours and then finished into a round bar having a diameter of 60 mm by hot working. The round bar of each material is hot-rolled at a temperature of 1373K and finished into a round bar having a diameter of 15 mm for forming a friction member. The six types of JIS standard stainless steel materials are round bars prepared for forming a comparative friction member. Here, each of the first and second manufacturing materials has a Ti (titanium) content outside the scope of the present invention.

  Each of the eleven kinds of round bars is cut into a ring-shaped member having a predetermined dimension in order to obtain the friction member 6 as shown in FIG. Here, each round bar was finished into a ring-shaped member having dimensions of an outer diameter of 10 mm, an inner diameter of 7.2 mm, and a thickness of 0.5 mm.

  That is, a ring-shaped member having three types of compositions according to the embodiment of the present invention, a ring-shaped member having two types of compositions whose Ti content is outside the scope of the present invention, and a composition of six types of comparative stainless steels A total of eleven types of ring-shaped members were produced as the friction member 6.

  Of the manufactured friction members, three types of friction members according to the embodiment of the present invention and two types of friction members made of the first and second manufacturing materials are used at a temperature of 823 K for 2 hours. Ion nitriding treatment was performed. Similarly, a friction member made of SUS303, SUS304, SUS303 (Se), or SUS316L austenitic stainless steel was similarly subjected to an ion nitriding treatment at a temperature of 823 K for 2 hours. In contrast, a friction member made of SUS440A and SUS420j2 martensitic stainless steel was subjected to an ion nitriding treatment at a temperature of 743 K for 7.5 hours.

  In order to use the friction member subjected to these ion nitriding treatments as the friction member of the ultrasonic motor described above, it is necessary to finish the surface of the nitride layer smoothly. However, here, the following tests are carried out on each friction member without performing surface finishing, and the results are described.

  Each friction member subjected to the ion nitriding treatment was embedded in a resin, and a Vickers hardness test was performed on the cross section. As a result of this test, it was found that each material maintained a sufficient hardness of around 1200 Hv at a depth of 20 μm from the surface, and regarding the hardness, there was almost no difference due to each composition.

  Moreover, after the cross section of each friction member was etched using a nital liquid composed of nitric acid and ethyl alcohol, the cross sections after the treatment were observed with a microscope. By this microscopic observation, what was shown in FIGS. 1-11 was obtained as a microscope picture which image | photographed the cross section of each friction member. Each of the micrographs in FIGS. 1 to 3 is of the friction member according to the first embodiment, the second embodiment, and the third embodiment. Each of the micrographs in FIGS. 4 and 5 is of a friction member made of the first manufacturing material and the second manufacturing material. Each of the micrographs in FIGS. 6 to 11 is of a friction member made of SUS440A, SUS303, SUS420j2, SUS304, SUS303 (Se), and SUS316L. Here, SUS303 and SUS303 (Se) contain manganese sulfide and selenium as free-cutting components, respectively.

  In each of the micrographs of FIGS. 1 to 11, a nitrided layer 101a is projected near the center, and a stainless steel base material 101 is projected on the upper portion thereof. The nitride layer 101a has a thickness of about 30 μm for each material, and it was confirmed that there is almost no difference in the thickness of the nitride layer due to the difference in material. Further, a sagging prevention material 102 is provided below the nitride layer 101a. This is a material embedded in contact with the nitride layer to clarify the surface portion of the nitride layer 101a, and is directly related to the present invention. Does not matter.

  As can be seen from these micrographs, the base material 101 that is not nitrided in all 11 types of friction members maintains a glossy state that is hardly corroded. However, among the friction members, there is a friction member in which the entire nitride layer 101a is corroded black. This means that the nitrided layer 101a that has been corroded is more easily corroded than the base material 101 that is not nitrided even in the atmosphere.

  In addition, there is a friction member in which the boundary between the nitride layer 101a and the base material 101 is not clear. Such a friction member indicates that the nitride layer 101a is hardly corroded.

  As for the ring-shaped members (friction members) of the first to third embodiments, the boundary between the nitrided layer 101a and the base material 101 is clear as can be seen from the cross-sectional micrographs shown in FIGS. Not. On the other hand, in the friction member made of comparative stainless steel shown in FIGS. 6 to 11, the nitride layer 101a corrodes and the boundary between the nitride layer 101a and the base material 101 is clear. This clearly indicates that the nitride layer 101a of the friction member according to the first to third embodiments is obviously less corroded than the nitride layer 101a of the comparative friction member.

  Further, the friction member made of the first and second manufacturing materials contains more Ti than the friction members according to the first to third embodiments, and the corrosion resistance of the nitride layer 101a. It is understood that is very excellent. However, as will be described later, these friction members are cracked and cannot be said to be reliable.

  The nitride layer 101a of the friction member of the first embodiment and the peripheral portion of titanium sulfide crystallized in the base material 101 are slightly corroded. That is, in the peripheral part where titanium sulfide was generated, Ti in the base material 101 was used for the generation of titanium sulfide, so it is considered that the titanium content in that part was deficient.

  However, all the friction members made of the first embodiment, the second embodiment, the third embodiment, the first manufacturing material, and the second manufacturing material are all corrosion resistant of the nitrided layer. It can be seen that is superior to other materials. The cause is not clear, but it is presumed that the presence of Ti acted to improve the corrosion resistance. Since Ti is a nitride-forming element that easily forms a compound with nitrogen, it is considered that the precipitation of the compound of chromium and nitrogen was delayed. If Ti is first bonded to nitrogen to form titanium nitride, precipitation of chromium and nitrogen compounds can be suppressed, and the aforementioned sensitization phenomenon can also be suppressed.

  Here, if Ti delayed the precipitation of the compound of chromium and nitrogen is due to exhibiting excellent corrosion resistance, niobium, vanadium, boron, It is presumed that the same effect can be obtained even in the case of a nitride-generating element such as zircon.

  Next, a preferred component range of the nitride member according to the embodiment of the present invention will be described.

  Ni (nickel) is an austenite generating element. In order to obtain an austenite-only phase, it is necessary to add Ni by 5.0% by weight or more. When the amount of Ni exceeds 15.0% by weight, formation of a nitride layer is inhibited. Therefore, the amount of Ni is preferably in the range of 5.0 to 15.0% by weight.

  Cr (chromium) is an essential element for stainless steel, and if the amount is less than 15.0% by weight, the corrosion resistance is lowered. On the other hand, if the amount of Cr exceeds 25.0% by weight, a two-phase structure of ferrite and austenite is formed, and the good plastic workability inherent to austenite deteriorates. Therefore, the amount of Cr is preferably in the range of 15.0 to 25.0% by weight.

  Ti (titanium) is an element added to improve the corrosion resistance of the nitrided layer, and an effect is recognized if it is added at least 0.8% by weight or more. Conversely, if Ti is added excessively, the cost increases. Further, the first and second production materials are those in which Ti is added by 4.0 wt% or more. As shown in FIGS. 12 to 14, Ti elements are unevenly distributed and along the nitride layer. Many cracks that occurred were confirmed. That is, it was found that when the Ti content was 4.0% by weight or more, the purpose as the nitride layer could not be achieved.

  Here, when the entire nitrided layer of the friction member (shown in FIG. 5) made of the second manufacturing material having a Ti content of 4.92% by weight is scanned with a scanning electron microscope, two layers as shown in FIG. A secondary electron image is obtained. In this secondary electron image, it can be seen that most of the area is occupied by the nitride layer 101a, and the cracks run sideways. In addition, in the secondary electron image, contrast is generated when the composition (component) is different. Therefore, in the secondary electron image shown in FIG. 12, unevenness of the component occurs in each of the gray portion and the white portion. I understand.

  In the secondary electron image shown in FIG. 12, the images shown in FIGS. 13 and 14 are obtained as images in which N (nitrogen) and Ti are mapped. From these mapping images, it can be seen that where N is large, Ti is also large. Moreover, although it seems that the compound TiN is not produced | generated yet, the uneven distribution of such a component is not preferable at least. Therefore, the Ti content is desirably 3.0% by weight or less.

  On the other hand, the friction member of the first embodiment contains 1.02% by weight of Ti, but the content of 0.15% by weight of titanium is 0.209% by weight. Percentage of sulfur consumed. Therefore, in the case of a composition in which the content of sulfur is suppressed to a low level, it is assumed that the effect of improving the corrosion resistance will be obtained if Ti is contained in an amount of 0.8% by weight or more.

  This is substantially the same composition as the first embodiment, and does not contain Ti, SUS303 (FIG. 7) and SUS304 (FIG. 10), and the first embodiment (FIG. 1). Is clear. That is, if at least Ti is contained in an amount of 0.8% by weight or more, an effect is seen in improving the corrosion resistance.

  Here, the effect of improving the corrosion resistance of the friction member in the case of ion nitriding has been confirmed. If this improvement in corrosion resistance is due to the above-described factors, it is assumed that the same effect can be expected even if other nitriding treatments such as gas nitriding treatment and salt bath nitriding treatment are performed.

  In the embodiment of the present invention, the nitriding member in the case where the friction member 6 of the rod-type ultrasonic motor shown in FIG. 18 is formed has been described. However, the friction member 26 of the annular ultrasonic motor shown in FIG. Can be formed of the same nitriding member, and the same effect can be obtained.

  In the embodiment of the present invention, the example in which the ion nitriding treatment is performed at a temperature of 823 K is shown. However, the ion nitriding treatment may be performed at a temperature exceeding 773 K.

  Here, the temperature of the ion nitriding process will be described.

  Three samples were manufactured for each of the first to third embodiments. Specifically, as shown in FIG. 15, the three samples corresponding to the first embodiment are sample Nos. 500-1, 530-1, and 550-1 were manufactured. As three samples corresponding to the second embodiment, sample No. 500-2, 530-2, and 550-2 are sample Nos. 3 as three samples corresponding to the third embodiment. 500-3, 530-3, and 550-3 were produced. Of these samples, sample No. Each of 500-1, 500-2, and 500-3 was subjected to nitriding treatment at a temperature of 773K for 6 hours. Sample No. Each of 530-1, 530-2, and 530-3 was subjected to nitriding for 5 hours at a temperature of 803K. Sample No. Each of 550-1, 550-2, and 550-3 was subjected to nitriding for 4 hours at a temperature of 823K.

  Here, as shown in FIG. 15, the thickness of the nitride layer formed on each sample 500-1, 500-2, 500-3 by nitriding treatment at a temperature of 773 K for 6 hours is 30 μm or less, This is not practical.

  Further, the hardness (Hv) of the nitride layer formed on each sample by each nitriding treatment shows a hardness of 1080 Hv or more at a position of 20 μm from the surface, as shown in FIG. Moreover, even in the case of nitriding at a high temperature of 823 K, the hardness is not reduced.

  As described above, if the three types of austenitic stainless steel materials constituting the first to third embodiments are used, a practical thickness can be obtained even in a nitriding process at a high temperature, which is generally considered to deteriorate the corrosion resistance. And a nitride layer having corrosion resistance could be obtained.

  As described above, according to the present invention, it is possible to obtain a nitrided member having good workability, excellent corrosion resistance, and a thick nitride layer formed thereon. Specifically, with respect to workability, austenitic stainless steel inherently has excellent plastic workability, and thus can be formed by a method suitable for mass production such as press working. In addition, a nitriding layer having a corrosion resistance comparable to that of the base material can be formed by subjecting this stainless steel material to nitriding treatment. Since the nitrided layer of the material has high corrosion resistance, a thick nitrided layer can be obtained while maintaining practical corrosion resistance even when nitriding is performed at a high temperature exceeding 773K.

It is a figure which shows the microscope picture of the cross section of the friction member which consists of a nitriding member which concerns on the 1st Embodiment of this invention. It is a figure which shows the microscope picture of the cross section of the friction member which consists of a nitriding member which concerns on the 2nd Embodiment of this invention. It is a figure which shows the microscope picture of the cross section of the friction member which consists of a nitriding member which concerns on the 3rd Embodiment of this invention. It is a figure which shows the microscope picture of the cross section of the friction member which consists of the nitride member of the 1st manufacturing material which made content of Ti out of the range of this invention. It is a figure which shows the microscope picture of the cross section of the friction member which consists of the nitride member of the 2nd manufacturing material which made content of Ti out of the scope of the present invention. It is a figure which shows the microscope picture of the cross section of the friction member which consists of SUS440A. It is a figure which shows the microscope picture of the cross section of the friction member which consists of SU303. It is a figure which shows the microscope picture of the cross section of the friction member which consists of SUS402j2. It is a figure which shows the microscope picture of the cross section of the friction member which consists of SUS304. It is a figure which shows the microscope picture of the cross section of the friction member which consists of SUS303 (Se). It is a figure which shows the microscope picture of the cross section of the friction member which consists of SUS316L. It is a figure which shows the electron micrograph of the nitride layer part of the 2nd manufacturing material of FIG. It is a figure which shows the mapping image of N in the nitride layer part of FIG. It is a figure which shows the mapping image of Ti in the nitride layer part of FIG. It is a figure which shows the graph which shows the thickness of the nitride layer when carrying out nitriding treatment at each temperature. It is a figure which shows the graph which shows the hardness of the nitrided layer when it nitrides at each temperature. It is a perspective view which shows the external shape of the friction member which consists of a nitriding member which concerns on one embodiment of this invention. It is a longitudinal section showing the composition of a rod type ultrasonic motor. (A) is a figure which shows typically the vibration mode of the rod-shaped ultrasonic motor of FIG. 18, (b) is a figure which shows a vibration mode typically. (A) is a longitudinal cross-sectional view showing a configuration of an annular ultrasonic motor, and (b) is a perspective view of a vibrator.

Explanation of symbols

1, 21 Elastic body 6, 26 Friction member 7 Rotor 27 Moving body 101 Non-nitrided base material 101a Nitride layer

Claims (6)

Austenitic stainless steel containing 0.8 to 3.0% by weight of Ti, 5.0 to 15.0% by weight of Ni, 15.0 to 25.0% by weight of Cr, and 0 to 0.209% by weight of S And having a nitride layer thicker than 30 μm on the surface,
The nitride member has a Vickers hardness of 1080 Hv or more at a position of 20 μm from the surface.   2. The nitride member according to claim 1, wherein the nitride layer is not substantially corroded when the cross-section is etched using a nital liquid composed of nitric acid and ethyl alcohol. 3. Austenitic stainless steel containing 0.8 to 3.0% by weight of Ti, 5.0 to 15.0% by weight of Ni, 15.0 to 25.0% by weight of Cr, and 0 to 0.209% by weight of S And having a nitride layer thicker than 30 μm on the surface,
The friction member, wherein the nitride layer has a Vickers hardness of 1080 Hv or more at a position of 20 μm from the surface.   4. The friction member according to claim 3, wherein the nitride layer is not substantially corroded when the cross section is etched using a nital liquid composed of nitric acid and ethyl alcohol. 5. A vibrator whose vibration is excited by an electromechanical energy conversion element;
A mover driven by vibration excited by the vibrator;
A friction member provided on at least one of the vibrator and the mover so as to be in contact with the other;
The friction member is composed of 0.8 to 3.0% by weight of Ti, 5.0 to 15.0% by weight of Ni, 15.0 to 25.0% by weight of Cr, and 0 to 0.209% by weight of S. An austenitic stainless steel containing a nitride layer thicker than 30 μm on the surface;
The vibration wave driving device according to claim 1, wherein the nitride layer has a Vickers hardness of 1080 Hv or more at a position of 20 μm from the surface.   6. The vibration wave driving device according to claim 5, wherein the nitride layer is not substantially corroded when a cross-section is etched using a nital liquid composed of nitric acid and ethyl alcohol.