JPH0712988B2 - Silicon-containing non-oxide ceramic protective layer and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Prior Art] Recently, silicon-containing non-oxide ceramics such as silicon nitride and silicon carbide have been noted for their excellent properties such as high strength, corrosion resistance, and heat resistance. It has come to be used for. As a result, silicon-containing non-oxide ceramics are also used in sliding members such as ceramic engines. When the sliding member is formed of ceramics, the sliding portion is polished with diamond or alumina.

[Disadvantages of Prior Art] However, when polishing silicon-containing non-oxide ceramics using diamond or alumina, many surface scratches are formed and brittle fracture easily occurs. In addition, the surface roughness is as large as 50 nm or more, and as a result, stress is unevenly applied, stress concentration occurs, and the wear rate increases.

[Problems to be Solved by the Invention] An object of the present invention is to provide a smooth protective layer of silicon-containing non-oxide ceramics used as a sliding member and having a small friction coefficient, and a method for producing the same.

[Structure of the Invention] That is, the present invention provides a protective layer formed on a silicon-containing non-oxide ceramic and made of amorphous hydrated silicon dioxide represented by the following general formula.

(Wherein A is an atom in the silicon-containing non-oxide ceramics or an oxygen atom bonded to an atom in the silicon-containing non-oxide ceramics, n is an integer of 0 to 2000, and m is a number of 1 or more). The present invention also provides a method for producing the protective layer, which comprises rubbing silicon-containing non-oxide ceramics together in the presence of water molecules.

EFFECTS OF THE INVENTION According to the present invention, a protective layer made of amorphous hydrated silicon dioxide having a very smooth surface with a surface roughness of 10 nm or less and a friction coefficient of about 0.001 is a silicon-containing non-oxide. Offered on ceramics. As a result, the brittle fracture of the silicon-containing non-oxide ceramic is eliminated, the stress is evenly distributed, and the wear rate is significantly reduced. Therefore, when the silicon-containing non-oxide ceramics protected by the protective layer of the present invention is used as a sliding part of an adiabatic diesel engine or gas turbine engine, as a wear resistant tool, their durability is greatly increased, and When this is used in an engine, the friction of the sliding portion is reduced, so that an efficient engine can be obtained.

[Detailed Description of the Invention] As described above, the protective layer of the present invention is represented by the following general formula.

In the formula, A is an atom in the silicon-containing non-oxide ceramics,
Alternatively, it represents oxygen bonded to an atom in the silicon-containing non-oxide ceramics. That is, when the silicon-containing non-oxide ceramic is Si ₃ N ₄ , A represents Si or N constituting Si ₃ N ₄ , or O bonded to Si or N. Similarly,
If the silicon-containing non-oxide ceramic is SiC, A is S
Indicates Si or C constituting iC, or O bonded to Si or C. n represents the number of repeating units sandwiched by two broken lines in the formula (the number of repeating units in the longitudinal direction of the paper), and is 0 to 20.
It is an integer of 00. m represents the number of repeating units enclosed in parentheses in the formula and is 1 or more. Since m represents the width of the protective layer in the lateral direction, it has no particular upper limit and does not have to be an integer. Since this hydrated silicon dioxide layer is amorphous, the atomic arrangement is irregular.

The protective layer of the present invention can be formed by rubbing silicon-containing non-oxide ceramics in the presence of water molecules. This rubbing operation is preferably carried out in water, but it can also be carried out in moist air. The rubbing operation is preferably carried out at a temperature of 20 ° C to 100 ° C. The friction load is about 200 grams to about 10 kilograms, and the sliding speed is about 1 cm / sec to about 50c.
m / sec is preferred. The slip distance is preferably about 2 m to about 2700 m.

[Examples of the Invention] Example 1 Si ₃ N ₄ was rubbed at a temperature of 20 ° C. in argon with a relative humidity of 98% under a load of 1 kg and a sliding speed of 1 mm / sec for 20 minutes. When the friction surface was observed with a scanning electron microscope, an extremely smooth surface was obtained and there was almost no surface damage. The surface roughness of this surface was measured by a stylus type surface roughness measuring device (trade name Talysurf) and found to be 10 nm or less. Furthermore, when the friction coefficient of this surface was measured, it was about 0.
Was 7. The friction coefficient was measured with a pin / disk type friction tester.

The friction surface thus obtained was analyzed by scanning Auger electron spectroscopy based on a conventional method. The analysis conditions are as follows.

Electron beam voltage: 5kV Scanning frequency: 6 times Argon sputtering (ion beam energy): 3
The kV results are shown in FIGS. 1 and 2. For comparison, Si ₃ N ₄ without friction was also analyzed. This result is the third
Shown in Figures and 4. As shown in FIG. ₃ , Si ₃ N ₄
Then, the peak of Si (the peak goes down in the drawing)
(83 eV), N peak 379 eV and O peak 503 eV appear (because the O peak appears, it is considered that some SiO ₂ is included). The peak of Si at 83 eV means that
Indicates that N is linked to N. On the other hand, on the friction surface, which is the protective layer of the present invention, Si peak 76 eV and O peak 503 eV appear as shown in FIG.
Peak does not appear. Si peak is 76eV instead of 83eV
Further, as shown in FIG. 2 (enlarged view near the Si peak), the further appearance of the peak of 59 eV indicates that Si and O are bonded, and the friction surface is
It can be seen that it is SiO ₂ .

No hydrogen was detected by this scanning Auger electron spectroscopy. However, (1) the rubbing surface does not form unless it is rubbed in the presence of water molecules, ie, rubbing in dry air or dry oxygen does not produce the rubbing surface, and (2) The abrasion powder dissolves in water, and when the water is dried, it becomes a transparent film, but SiO ₂ is extremely difficult to dissolve in water, and when it becomes hydrated, it becomes more easily soluble. It can be identified as silicon dioxide.

An electron diffraction photograph was taken of the above friction surface using a 100 kV electron microscope based on a conventional method, and no diffraction image of crystals was obtained. From this, it can be seen that the friction surface is not in a crystalline state but in an amorphous state.

From the above experimental results, it is understood that the friction surface which is the protective layer of the present invention is amorphous hydrated silicon dioxide.

Further, the friction surface was subjected to EDAX analysis (energy dispersive X-ray analysis) by a conventional method using a 20 kV electron microscope. Originally, H, N, and O could not be detected by EDAX analysis, but it was conducted to investigate whether Mg or Fe used as a binder element in the ceramic manufacturing process is segregated on the friction surface due to friction. For comparison, the other surface, which was not rubbed, was also analyzed. As a result, only Si was detected on both sides. From this, it was found that the binder element was not segregated on the friction surface.

Example 2 The same experiment as in Example 1 was conducted using SiC. As a result, a smooth friction surface similar to that in Example 1 was obtained. This was analyzed in the same manner as in Example 1. The results of the scanning Auger electron spectroscopy analysis are shown in FIGS. 4 and 5. The SiC analysis results for comparison are shown in FIGS. 6 and 7. As shown in FIG. 6, in SiC without friction, a peak 95eV of Si and a peak 272eV of C appear. Also, the seventh
As shown in the figure (enlarged view near the Si peak), 59 eV
There is no peak in the vicinity. On the other hand, on the friction surface obtained by rubbing this in the presence of water molecules, as shown in FIG.
The Si peak moves to 78 eV, and the O peak 503 eV appears. Further, as shown in FIG. 5 (enlarged view near the Si peak), a peak is formed at 59 eV, which indicates that the friction surface is SiO ₂ . Although there is also a C peak in Fig. 4, it is 95eV which is the peak of Si bonded to C.
Since there is no peak at 1, it is considered that C is a stain such as CO or CO ₂ attached to the friction surface. Since other experimental results are the same as in Example 1, it can be identified that this friction surface is also amorphous hydrated silicon dioxide.

Example 3 Si ₃ N ₄ comrades were rubbed under the following conditions in air with a relative humidity of 50%.

Load: 1 kg Sliding speed: 1 mm / sec Sliding distance: 4 m (Sliding time 4000 seconds) Temperature: 25 ° C. As a result, an extremely smooth amorphous hydrated silicon dioxide layer having the same spectrum as in Example 1 was formed. It was

Example 4 Si ₃ N ₄ was rubbed under the following conditions in air with a relative humidity of 100%.

Load: 1 kg Sliding speed: 1 mm / sec Sliding distance: 4 m (Sliding time 4000 seconds) Temperature: 25 ° C. As a result, an extremely smooth amorphous hydrated silicon dioxide layer having the same spectrum as in Example 1 was formed. It was

Example 5 Si ₃ N ₄ comrades were rubbed under the following conditions in argon with a relative humidity of 80%.

Load: 1 kg Sliding speed: 1 mm / sec Sliding distance: 4 m (Sliding time 4000 seconds) Temperature: 25 ° C. As a result, an extremely smooth amorphous hydrated silicon dioxide layer having the same spectrum as in Example 1 was formed. It was

Example 6 Si ₃ N ₄ rubs with each other under the following conditions in air with relative humidity of 50%.

Load: 1 kg Sliding speed: 10 cm / sec Sliding distance: 180 m (Sliding time 1800 seconds) Temperature: 25 ° C. As a result, an extremely smooth amorphous hydrated silicon dioxide layer having the same spectrum as in Example 1 was formed. It was

Example 7 SiC rubs were rubbed under the following conditions in air with a relative humidity of 50%.

Load: 1 kg Sliding speed: 1 mm / sec Sliding distance: 4 m (Sliding time 4000 seconds) Temperature: 25 ° C. As a result, an extremely smooth amorphous hydrated silicon dioxide layer having the same spectrum as in Example 2 was formed. It was

Example 8 SiC rubs were rubbed under the following conditions in air with a relative humidity of 100%.

Load: 1 kg Sliding speed: 1 mm / sec Sliding distance: 4 m (Sliding time 4000 seconds) Temperature: 25 ° C. As a result, an extremely smooth amorphous hydrated silicon dioxide layer having the same spectrum as in Example 2 was formed. It was

Example 9 SiC rubs were rubbed under the following conditions in air with a relative humidity of 50%.

Load: 1 kg Sliding speed: 10 cm / sec Sliding distance: 180 m (Sliding time: 1800 seconds) Temperature: 25 ° C. As a result, an extremely smooth amorphous hydrated silicon dioxide layer having the same spectrum as in Example 2 was formed. It was

Example 10 Si ₃ N ₄ comrades were rubbed in water under the following conditions.

Load: 500g Temperature: 25 ℃ Slip rate and time: 1cm / sec for 20 minutes 3cm / sec for 20 minutes 5cm / sec for 20 minutes 7cm / sec for 30 minutes As a result, an extremely smooth surface with a surface roughness of 10nm or less can be obtained. Obtained and observed by a scanning electron microscope, the number of surface scratches was very small.

Example 11 Si ₃ N ₄ comrades were rubbed in water under the following conditions.

Load: 1000g Temperature: 50 ℃ Slip rate and time: 2cm / sec for 20 minutes 6cm / sec for 20 minutes 10cm / sec for 20 minutes 14cm / sec for 30 minutes As a result, an extremely smooth surface with a surface roughness of 10nm or less is obtained. Obtained and observed by a scanning electron microscope, the number of surface scratches was very small.

Example 12 A SiC plate was polished with Si ₃ N ₄ in water under the following conditions.

Load: 500g Temperature: 25 ℃ Sliding speed and time: 2cm / sec for 20 minutes 4cm / sec for 20 minutes 10cm / sec for 20 minutes 18cm / sec for 30 minutes As a result, surface roughness on the SiC plate of 10nm or less A smooth surface was obtained, which was observed with a scanning electron microscope and had very few surface scratches.

Example 13 A Si ₃ N ₄ plate was polished with a SiC bottle in water under the following conditions.

Load: 500g Temperature: 25 ℃ Sliding speed and time: 2cm / sec for 20 minutes 4cm / sec for 20 minutes 10cm / sec for 20 minutes 18cm / sec for 30 minutes As a result, the surface roughness on Si ₃ N ₄ plate is 10nm. The following extremely smooth surface was obtained, and when observed with a scanning electron microscope, surface scratches were very small.

Example 14 SiC members were rubbed in water under the following conditions.

Load: 500g Temperature: 25 ℃ Slip rate and time: 2cm / sec for 20 minutes 4cm / sec for 20 minutes 12cm / sec for 20 minutes 25cm / sec for 30 minutes As a result, surface roughness on SiC is extremely smooth with a surface roughness of 10nm or less. A smooth surface was obtained, and the surface scratches were very small when observed with a scanning electron microscope.

[Brief description of drawings]

FIG. 1 is a diagram showing a spectrum obtained when an amorphous hydrated silicon dioxide layer of the present invention obtained by rubbing Si ₃ N ₄ with each other was analyzed by a scanning Auger electron spectroscopy, FIG. 2 Is an enlarged view near the Si peak in Fig. 1, and Fig. 3 is for comparison.
FIG. 4 is a diagram showing a spectrum obtained by scanning Auger electron spectroscopy analysis of Si ₃ N _4, and FIG. ₄ is a scanning Auger showing the amorphous hydrated silicon dioxide layer of the present invention obtained by rubbing SiC The figure which shows the spectrum obtained when it analyzed by the electron spectroscopy, FIG. 5 is the enlarged view of the Si peak vicinity of FIG.
FIG. 6 is a diagram showing a spectrum obtained by performing scanning Auger electron spectroscopy on SiC for comparison, and FIG. 7 is an enlarged view of the vicinity of the Si peak in FIG.

Claims (3)

[Claims] 1. A protective layer formed on a non-oxide ceramic containing silicon and comprising amorphous hydrated silicon dioxide represented by the following general formula. (Wherein A is an atom in the silicon-containing non-oxide ceramics or an oxygen atom bonded to an atom in the silicon-containing non-oxide ceramics, n is an integer of 0 to 2000, and m is a number of 1 or more) 2. The silicon-containing non-oxide ceramic is Si
The protective layer according to claim 1, which is ₃ N ₄ or SiC. 3. A method for producing a protective layer comprising amorphous hydrous silicon dioxide, which comprises rubbing silicon-containing non-oxide ceramics together in the presence of water molecules.