JP4877502B2 - Nitrogen-containing Cr coating and mechanical member having this coating - Google Patents

Description

  The present invention relates to a nitrogen-containing Cr coating and a mechanical member having this coating.

  Many machine parts including molds are used under severe conditions, but the characteristics required for these machine parts are excellent wear resistance, excellent corrosion resistance, and excellent seizure resistance. Etc.

  In order to impart such characteristics, various surface treatments are usually applied to SKD (tool steel) which is a base material of such a machine member. One of them is hard chrome plating. Hard chromium plating has a surface hardness as high as an average Hv 1000 to 1100, but hexavalent chromium contained in the treated wastewater causes water pollution. Moreover, there was a problem in the adhesion between the plating film and the base material.

  In addition, when a Cr single layer coating is formed on the surface of the base material of the mechanical member by the PVD processing method, the adhesion between the base material and the coating is excellent, but the film hardness is as low as Hv 500 to 600. there were.

  In addition, mechanical members such as friction and wear parts used in engines and transmissions of motorcycles and automobiles are highly tough and have high toughness because they are repeatedly subjected to sliding contact and impact with a high-speed rotating body. Properties such as surface hardness and low friction coefficient are required.

  For these parts, low carbon steel or medium carbon steel is generally used, and surface treatments such as carburizing, quenching, and nitriding are performed to impart the above characteristics. Nickel-phosphorus plating, shot peening, thermal spraying of various metals, etc. are performed to improve wear resistance, seizure resistance, and lubricity.

  However, due to the recent reduction in weight and increase in engine output, it has been used in harsher environments, and the above-mentioned surface treatment cannot satisfy the required characteristics. In order to satisfy the above characteristics, TiN film or CrN film by ion plating method is being used among PVD methods. However, since the processing temperature is as high as 400 ° C. or higher, the hardness of the base material is lowered. However, there is a problem that satisfactory characteristics cannot be obtained.

  As described above, the conventional surface treatment method for mechanical members and the surface coating obtained thereby have problems in wear resistance, corrosion resistance, seizure resistance, lubricity, etc., and thus the life of the member itself is inferior. was there.

  The present invention has been made to solve the above-described problems of the coating film.

The film of the present invention is a Cr film containing nitrogen formed on the surface of a member to be processed, and is formed by sputtering chromium at a sputtering process temperature of less than 300 ° C. in an atmosphere of nitrogen. Cr _x N _y crystals containing 50 to 99 chromium atoms and 50 to 1 nitrogen atoms per atom are scattered, and the composition of the Cr _x N _y crystal is 52 chromium atoms per 48 atoms and 48 nitrogen atoms . It is characterized by including.

Hardness Hv of the nitrogen-containing Cr coating is characterized 1700-2000 der Rukoto.

The nitrogen-containing Cr coating has a thickness of 5 to 100 μm .

  The mechanical member of the present invention is characterized in that a nitrogen-containing Cr coating is formed on the surface thereof.

The mechanical member is a frictional wear part used in a mold, a powder molding punch, a piercing punch, a Cu coiling punch, a motorcycle or a motorcycle .

  As described above, according to the mechanical member of the present invention, not only can the life of the mechanical member be greatly extended, but also its releasability is improved, which can greatly contribute to effective utilization of resources and reduction of pollution problems. And so on.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a coating film according to the present invention, a manufacturing method thereof, and a mold as an example of a mechanical member having the coating film will be described with reference to the drawings.

  FIG. 1 is a schematic view of a sputtering apparatus for forming a coating film of the present invention on a mold. Reference numeral 1 denotes a cylindrical or square vacuum processing chamber, and 2 denotes a vacuum for the inside of the vacuum processing chamber 1. A vacuum pump, 3 is a rotary table disposed at the center of the vacuum processing chamber 1, 4 is a mold as a member to be processed placed on the rotary table 3 via a jig 5, and 6 is a workpiece to be processed. A chromium target as an evaporation source arranged so as to surround the mold 4, a DC sputtering power source connected to the chromium target 6, 8 a DC ion bombard and bias power source connected to the rotary table 3, and 9 It is a gas introduction pipe for introducing argon and nitrogen gas into the vacuum processing chamber 1.

  In the present invention, vacuum degassing is performed before the sputtering process.

In the present invention, nitrogen gas and argon gas are introduced into the vacuum processing chamber 1 through the gas introduction pipe 9, and then chromium is sputtered onto the surface of the member to be processed, for example, the mold, and the surface of the mold is subjected to nitrogen. A Cr film containing 50 to 99 chromium atoms and 100 to 1 nitrogen atoms and containing Cr _X N _Y crystals is produced as a Cr film containing Ni. In the sputtering, it is preferable to keep the distance between the target and the material to be processed at, for example, 70 mm in order to make the thickness of the coating film uniform and to keep the temperature of the member to be processed below the tempering temperature.

  In the present invention, ion bombarding is performed as necessary before the sputtering process, the process temperature is set to less than 300 ° C., the processing time is determined according to the thickness of a predetermined film, and the texture of the film is adjusted during the process. This is done by changing the pressure and bias voltage. When the process temperature is 300 ° C. or higher, the base material itself is softened. Therefore, a low temperature is preferable for this treatment. However, it is not practically practical to perform the treatment at room temperature or lower because it is difficult to ensure adhesion.

  Note that the thickness of the coating is preferably up to 100 μm.

  When the chemical composition of the film on the surface was examined by EPMA, the ratio of Cr72, N28 and Cr52, N48, etc. was shown. Regarding the characteristics of the film, the seizure resistance, the wear resistance, the friction coefficient, the adhesion and the like were investigated.

  (Comparative example)

  As Comparative Examples 1 and 2, ion-plated TiN films and electrolytic hard chrome plating films were used.

  The seizure resistance was measured using a Fabry tester as shown in FIG. That is, each test pin 10 having a carburizing, quenching and tempering finish on SCM415 having a diameter of about 6.4 mm is coated with the present invention coating of 6 μm, and a V block 11 having a carburizing, quenching and tempering surface finish on SCM415 is used. Intermittent operation was carried out with a constant weight of 600 kgf. The intermittent operation is a condition of 2 seconds ON, 10 seconds OFF, a sliding speed of 0.1 m / sec, and no lubrication. In the evaluation method, the number of interruptions until the film was broken was evaluated as the seizure property.

  Reference numeral 12 denotes a driving machine that rotates the test pin 10 at, for example, 300 rpm, and reference numeral 13 denotes a shear pin for fixing the test pin 10 to the driving machine 12.

In addition, as wear characteristics, aggressive resistance characteristics were evaluated. Using a Suga type wear tester (NUS-ISO-3 type), a reciprocating wear test was performed using a # 400 diamond electrodeposited polishing cloth. All base materials are mirror-finished SUS440C. The total load of the test piece is 9.8 N, and the reciprocating stroke length is 60 mm. The abrasion characteristics were evaluated as the amount of abrasion (× 10 ⁻⁵ g / cm) of the sample.

  Table 1 shows the results.

  In Table 1, for example, 30 <is the number of times until destruction is 30 or more, and 5> is 5 or less.

  Furthermore, as an example of the member having the coating film of the present invention, the mold was subjected to sputtering treatment.

The ion bombardment treatment in the present invention was performed at 1250 V × 0.01 mA for about 40 minutes as 2 × 10 ⁻² torr in an Ar atmosphere.

In the sputtering treatment, the gas partial pressure in the atmosphere is Ar: 1.2 × 10 ⁻³ torr, N2: 0.2 × 10 ⁻³ torr, bias voltage: −90 to −100 V, and the treatment time is about 100. Minutes.

  In this invention, the metal mold | die which performed the sputtering target process to the tool steel which is a base material on the above conditions was created.

  In addition, about said conditions, it changes with the materials of a base material, a dimension, and a shape. In the case of the present embodiment, if the above conditions are not satisfied, the adhesion of the film and the characteristics of the film are inferior.

  The film obtained under these conditions had a hardness of Hv = 1700 to 2000, and the thickness of the obtained film was 10 μm.

  Table 2 shows a comparative example in use with a conventional mold. Regarding the service life, the present invention is compared with the conventional mold by the number of shots of the molded product when the separation of the mold becomes worse when actually punching.

  Table 2 shows the service life of dies and punches of various materials.

  In Table 2, for example, a life ratio of 10 <indicates that the life is extended by 10 times compared to the conventional one. SKD (HQT) indicates a quenching / tempering SKD material.

  Hereinafter, another embodiment of the present invention in which the coating of the present invention is applied to frictional wear parts used in engines and transmissions of motorcycles and automobiles will be described.

  As Comparative Examples 3, 4 and 5, ion-plated TiN film, CrN film and electrolytic hard chrome plating film were used.

  The coefficient of friction and seizure resistance were measured using a Fabry tester as shown in FIG. That is, the test pin 10 carburized and quenched and tempered and polished in an SCM415 having a diameter of 6.4 mm was used, and the V-block 11 was applied to the SCM415 and carburized and tempered and polished on the surface of the SCM415. A test was conducted in which the tightening load was increased from 0 to 25 kg / sec. The test was conducted in oil, and the friction coefficient and seizure resistance load at this time were evaluated. Table 3 shows the results.

  In consideration of applying the coating of the present invention to a motorcycle shift fork as a frictional wear part, a frictional wear test was conducted, and the wear amount of the product of the present invention was compared with that of Comparative Examples 6-9. The coating conditions at this time were: carburizing, quenching and tempering with a base material of SCM415, polishing lapping, adjusting the surface roughness to Ra 0.2, and processing the coating of the present invention to a thickness of 5 to 10 μm. In addition, the friction and wear test is performed by examining the friction and wear with the material (shifter) of the counterpart of the shift fork in an actual motorcycle. Here, a plate-on-disk test is performed as the friction and wear test, which corresponds to the shifter. The surface treatment of the part was machined, carburized and shot blasted.

  In the frictional wear test used in the present invention, after turning the turntable corresponding to the shift fork with a predetermined load on the turntable corresponding to the shifter and rotating only the turntable for a predetermined time, The amount of wear of the product is measured, and this amount of wear is evaluated as the amount of decrease in the film thickness of the coating on the friction surface of the test piece.

  Specifically, the base material of the article to be processed: SCM415 is carburized, quenched, and tempered, and then polished and lapped, and the surface roughness is adjusted to Ra = 0.2, and then obtained by the method of the present invention. A nitrogen-containing coating with a thickness of 5 μm is used as a test product, and the other turntable is obtained by shot blasting after the surface of the surface in contact with the workpiece is machined and carburized. Used. The load was 80 kgf, the sliding speed was 13 m / sec, and the time was 20 hours.

  The friction conditions were a 20-hour endurance test with a maximum load of 80 kgf and a sliding speed of 13 m / sec.

  In the evaluation after the test, the amount of wear on the friction surface was evaluated as the amount of film thickness reduction. The evaluation results are shown in Table 4.

  In Table 4, hard chrome plating (film thickness 30 μm) as comparative example 6, TiN (film thickness 5 μm) made by ion plating as comparative example 7 (film thickness 5 μm), CrN made by IP (film thickness 6 μm) as comparative example 8 As Comparative Example 9, a Mo sprayed (100 μm thick) product was used.

It is explanatory drawing of the surface treatment apparatus of the mechanical member of this invention. It is explanatory drawing of a Fabry testing machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum processing chamber 2 Vacuum pump 3 Rotary table 4 Die to be processed 5 Jig 6 Chromium target 7 Sputtering power supply 8 DC bias power supply 9 Gas introduction pipe 10 Test pin 11 V block 12 Driver 13 Shear pin

Claims (5)

A Cr film containing nitrogen formed on the surface of a member to be processed, which is formed by sputtering chromium in a nitrogen atmosphere at a sputtering process temperature of less than 300 ° C. Cr _x N _y crystals containing chromium atoms and 50 to 1 nitrogen atoms are interspersed, and the composition of the Cr _x N _y crystals contains 52 chromium atoms and 48 nitrogen atoms per 100 atoms. Nitrogen-containing Cr coating.   The nitrogen-containing Cr coating according to claim 1, wherein the nitrogen-containing Cr coating has a hardness Hv of 1700 to 2000.   The nitrogen-containing Cr coating according to claim 1 or 2, wherein the nitrogen-containing Cr coating has a thickness of 5 to 100 µm.   A machine member comprising the surface of the nitrogen-containing Cr coating according to claim 1.   5. The mechanical member according to claim 4, wherein the mechanical member is a friction wear part used in a mold, a powder molding punch, a piercing punch, a Cu coiling punch, a motorcycle or an automobile. .

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