JPS643951B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to channel-type and pinpoint-type porous chrome plating used for high-speed sliding parts such as engine parts, valves, seal rings, and bearings. This invention relates to a highly durable and wear-resistant sliding member with improved wear resistance and seizure resistance. [Prior art and problems] Conventionally, sliding parts such as cylinder liners, piston rings, piston rods, valves, and valve guides of various engines such as gasoline engines and diesel engines have been made of sliding members made of hard chrome plating on a metal base material. is mainly used. However, in recent years, problems such as abnormal wear and seizure of hard chrome plating have been occurring due to higher speeds and higher loads of automobiles, ships, and other industrial vehicles, as well as lower quality fuels. Improvements in performance are desired. On the other hand, many methods have been proposed and are being considered for practical application, in which ceramics or a composite material of metal and ceramics is thermally sprayed onto a metal substrate to apply the properties of ceramics, such as heat resistance and abrasion resistance, to sliding parts. There is. This thermal spray coating uses a mechanical bond to adhere to the metal base material, so the bond strength between the coating film and the base material is relatively weak, and when used under strong vibrations or thermal cycles, it may cause peeling damage and damage to the coating. It is necessary to perform a polishing finish to adjust the uniform thickness and smoothness of the coating, resulting in problems such as high costs. [Means and effects for solving the problems] As a result of extensive research in order to solve these problems and obtain a sliding member with excellent wear resistance and seizure resistance, the present inventor has developed a metal base material. The present invention was made based on the discovery that the purpose could be achieved by filling ceramics into the countless minute grooves and minute depressions such as pits that exist in porous chrome plating. . That is, the present invention provides a method for applying Cr ₂ O ₃ ceramics, SiO ₂ , Al ₂ O ₃ , SiC, Si ₃ N ₄ , LiF, CaF ₂ to minute recesses formed in porous chromium plating coated on the surface of a metal substrate.
at least one compound selected from
This is a wear-resistant sliding member that is filled with a composite ceramic of Cr ₂ O ₃ and has a sliding surface formed of a hard chromium surface and a ceramic surface. The metal substrate used in the present invention is an iron-based metal,
Examples include gray cast iron, spheroidal graphite cast iron, and carbon steel. The porous chrome plating applied to the surface of these metal substrates is generally applied as a channel type, pinpoint type, or intermediate type with a predetermined porosity using a method conventionally used for sliding parts of various engines. It is commercially available and can be easily obtained. Next, among the ceramics to be filled into the minute recesses of porous chrome plating, the Cr ₂ O ₃ ceramic source is
A concentrated aqueous _H2CrO4 solution prepared by dissolving 100 parts _by weight of _Cr2O3 in 65 parts by weight _of water and adjusting the specific gravity to 1.65 to 1.7 with water is used. Also, SiO ₂ , ZrO ₂ , Al ₂ O ₃ , SiC,
In the composite ceramic source of Cr ₂ O ₃ and at least one compound selected from Si ₃ N ₄ , LiF, and CaF ₂ , each ceramic source has a particle size of 10 μm or less, preferably an average particle size. Powder with a particle size of 3 μm or less is preferable, and ZrO ₂ is stabilized by stabilization treatment.
ZrO ₂ and Al ₂ O ₃ are preferably α-Al ₂ O ₃ , and Cr ₂ O ₃ is prepared and used in a concentrated aqueous solution as described above, and this concentrated aqueous solution and each of the above ceramic powders are used. is used as a slurry. In order to form ceramics in the minute recesses of porous chrome plating using such a ceramic source, a slurry consisting of a Cr ₂ O ₃ concentrated aqueous solution alone or a ceramic source powder and this is first applied. As a pretreatment of the part, the surface other than the chrome-plated surface is masked with organic paint or tape to prevent the ceramic source from adhering to it, and then immersed in the above-mentioned concentrated aqueous solution or slurry to remove minute defects such as channel grooves and pits on the plating surface. Fill the recess with a ceramic source. This filling can be carried out under normal pressure, but under reduced pressure of 0.1 to 1 mmHg or 2 to 4 mmHg.
It is preferable to maintain the pressure under a pressure of Kg/cm ² for 5 to 10 minutes, and after returning to normal pressure for 5 to 10 minutes, the member is taken out. Next, this treated material was sufficiently dried at 30 to 60°C, and the temperature was raised in a heating furnace at a heating rate of 7 to 10°C/min.
After heating for a minute and cooling, the ceramic film adhering to the plated surface is removed by buffing. Through this treatment, due to the bonding action of extremely fine Cr ₂ O ₃ produced by the decomposition of H ₂ CrC _{4 , Cr 2} O ₃ particles are bonded to each other or to the particles of the ceramic source powder.
A hardened body is formed as a composite ceramic made of particles, and this hardened body is firmly bonded to the inner surface of the fine recesses of the plating and to the metal base. Next, it is preferable to perform treatment with a concentrated aqueous solution of H ₂ CrO ₄ in order to strengthen the structure of the ceramic filled in the fine recesses of the plating. i.e.
Impregnating the pores of the ceramic with a concentrated aqueous solution of H ₂ CrO ₄ by brushing or dipping in the same manner as above,
After drying, a heating process is performed. Therefore, this treatment is carried out at least once, preferably 4 to 10 times.
It is desirable to repeat the process several times, thereby strengthening and densifying the ceramics, and simultaneously strengthening the bond between the ceramics and plating, or between them and the metal substrate. This treatment was performed under the same conditions as the ceramic filling treatment described above, and the deposits attached to the plating surface were reduced to 1 to 2.
It is preferable to remove it by buffing after each treatment. The number of repetitions of this H ₂ CrO ₄ concentrated aqueous solution is related to the hardness and density of the ceramics formed in the fine recesses of the plated surface, but the number of repetitions is relatively small, for example 3 to 4 times. In this case, some pores remain, which is advantageous for retaining lubricating oil. Furthermore, by subjecting ceramics containing CaF ₂ or LiF ₂ to a large number of treatments, for example 9 to 10 times, the ceramics become denser and harder. In this way, a dense ceramic layer with high hardness can be formed, and a wear-resistant sliding member with a low coefficient of friction can be obtained even in a high temperature range without lubricant. Although the porosity of porous chrome plating can be imparted with excellent heat resistance, wear resistance, and load resistance through the above treatment regardless of its size, it is preferably 15 to 50%. , the porosity is
If it is large, such as 30% or more, the channel width, length, depth, pit hole diameter _, etc. are large, so it is preferable to use _a slurry ceramic raw material. This makes it possible to reduce the number of times the process is performed to strengthen the bond between the plated portion, the plated portion, and the base metal. [Effect of the invention] Hard chrome plating has the lowest coefficient of friction among commonly used metal materials at room temperature, and has excellent wear resistance.On the other hand, Cr ₂ O ₃ or Cr ₂ Ceramics containing O ₃ have a small coefficient of friction at relatively high temperatures, and have excellent load resistance and seizure resistance. In particular, ceramics containing CaF ₂ , LiF, etc. The wear-resistant sliding member of the present invention can be made into a wear-resistant sliding member, but the wear-resistant sliding member of the present invention is made by applying porous chromium plating to a metal base member, and injecting Cr ₂ O ₃ ceramics or Cr into the minute recesses formed in the plating. Since it is formed by filling mixed ceramics containing ₂ O ₃ , different materials such as hard chromium and ceramics are strongly bonded to each other, and the bond with the metal substrate is also strengthened. By forming such a coating on the surface of the metal substrate,
A sliding surface with excellent load resistance, wear resistance, and seizure resistance can be obtained over a wide temperature range from low to high temperatures, and this can be easily obtained by using a relatively low heat treatment temperature and a simple treatment process. Moreover, it is recognized to have excellent effects, such as being able to easily produce parts with complex shapes and precision parts. Next, examples of the present invention will be described. Example 1 (1) Preparation of concentrated aqueous H ₂ CrO ₄ solution 100 parts by weight of CrO ₃ was dissolved in 65 parts by weight of water to prepare a concentrated aqueous solution of H ₂ OrO ₄ having a specific gravity of about 1.7. (2) Metal substrate (a) Cylindrical pin and V block for Farex friction and wear test Gray cast iron (FC-25), 6.5mmφ×
A pair of blocks with a 40mm cylindrical pin and a V groove (90° V groove 12mmφ groove depth 3.7m/m)
was prepared by applying channel-type porous chrome plating with a porosity of 25 to 30%. (b) Disc for Okoshi type friction and wear test A disc of 24 mmφ x 6 mm was prepared using cast iron (FC-35) by applying channel-type porous chrome plating with a porosity of 25 to 30%. (3) Formation of ceramics The porous chromium-plated metal substrate prepared in (2)-(a) and (b) was immersed in the H ₂ CrO ₄ concentrated aqueous solution prepared in (1), and then heated under a reduced pressure of 0.1 mmHg. Hold for 5 minutes, return to normal pressure, and leave to stand for another 7 minutes to fill the plating grooves and pits with the solution. Then, after drying at about 45℃ for 40 minutes,
The temperature was increased at a rate of 0.degree. C./min, and heat treatment was performed at 460.degree. C. for 30 minutes. As a result of this treatment, a thin Cr ₂ O ₃ film adhered to the plating surface, which was removed by buffing. Next, in order to impregnate the pores of the Cr ₂ O ₃ ceramic formed in the plating grooves and pits with the H ₂ CrO ₄ concentrated aqueous solution, the H ₂ CrO ₄ concentrated aqueous solution was impregnated and dried in the same manner as described above.
The heating process was repeated four times, and finally the sliding surface was buffed to produce a cylindrical pin and disk. (4) Friction and wear test (a) Test using Farex testing machine A pair of blocks (90° V groove, 12mmφ, depth 3.7mm) by applying a load from both sides and measuring the sliding friction. In other words, the temperature of the sample is maintained at 300℃, and the load is applied by rotating the ratchet gear.
The coefficient of friction was determined by increasing the load at a rate of 20 kgf/min, using an ester lubricating oil as the lubricating oil, and varying the load. The results are shown in the table below, and it was found that the load resistance (seizure resistance) was extremely excellent even at relatively high temperatures such as 300°C. (b) Okoshi method test The disk produced according to (3) is rotated, and a fixed mating material is pressed against this disk to measure sliding friction. In other words, a cast iron (FCD) cylindrical pin (4 mmφ) is used as the mating material.
Maximum pressing load 2.5Kgf (surface pressure 20Kg
f/cm ² ), silicone oil is used as the lubricant.
The oil was added dropwise at a rate of 4.0 ml/min. Note that the speed of the friction section was 3 m/min. The results are shown in the table below. From the above results, it was confirmed that the product of the present invention is a sliding member with much better wear resistance than the conventional one made only of hard chrome plating. Example 2 (1) Preparation of ceramic slurry Cr ₂ O ₃ , stabilized ZrO 2 , α-Al 2 O 3 , stabilized ZrO ₂ , α-Al ₂ O ₃ , all made into granular powder with a particle size of 6 μm or less and an average particle size of about 1 μm.
Using _CaF2 , 40 parts by weight _{of Cr2O3} , stabilized with _ZrO2 10
parts by weight, 10 parts by weight of α-Al ₂ O ₃ and 10 parts by weight of CaF ₂ were mixed with 25 parts by weight of a concentrated aqueous solution of H ₂ CrO ₄ prepared in the same manner as in Example 1-(1) and 30 parts by weight of pure water. death,
A slurry was prepared by grinding and mixing for 40 hours using an alumina ball mill. (2) Preparation of metal substrate A pair of cylindrical pins having V grooves were prepared in the same manner as in Example 1-(2)-(a) and (b), except that the porosity of the porous chrome plating was set to about 45%. Blocks and discs were prepared. (3) Formation of ceramics In the same manner as in Example 1-(3), filling the fine concavities of the plating with slurry, drying, and heat treatment were performed to form ceramics.
The H ₂ CrO ₄ concentrated aqueous solution treatment was repeated 7 times and buffed to form ceramics. (4) Friction and Wear Test The load resistance was examined using a Farex tester in the same manner as in Example 1-(4), and the abrasion resistance was measured using an Okoshi type tester. These results are shown in the table below. From these results, it was confirmed that the material has excellent wear resistance and load resistance over a wide temperature range. Comparative Example 1 Porosity 15 to 20 as in Example 1-(2)-(a) and (b)
A friction and wear test was conducted in the same manner as in Example 1-(4)-(b) using a metal member that had only been treated with hard chrome plating. The results are shown in the table below. Comparative Example 2 Porosity 25 to 30 as in Example 2-(2)-(a) and (b)
A friction and wear test was conducted in the same manner as in Example 1-(4)-(b) using a metal member that was only plated with hard chrome. The results are shown in the table below. 【table】

Claims (1)

[Claims] 1. Cr ₂ C ₃ ceramics or SiO ₂ , ZrO ₂ , Al ₂ O ₃ , SiC, Si ₃ N ₄ ,
A durable material characterized by being filled with a composite ceramic of Cr ₂ O ₃ and at least one compound selected from LiF and CaF ₂ and having a sliding surface formed of a hard chromium surface and a ceramic surface. Abrasive sliding members.