JPH01156461A - Surface treatment of piston ring - Google Patents

Abstract

PURPOSE:To provide satisfactory wear and seizing resistance to a piston ring and to improve the durability by forming a Cr2N type coating layer of a specified thickness by ion plating with gaseous nitrogen as a reactive gas and Cr as an evaporating material. CONSTITUTION:The base material 1 of each piston ring is held by a piston ring holder 4, rotated, heated and kept hot with a heater 5. Gaseous Ar is introduced from a gas introducing pipe 9 and the base material 1 is cleaned by sputtering. Cr 7 put in a crucible 6 is then evaporated with plasma beams and the resulting vapor is allowed to react with gaseous nitrogen introduced from the pipe 9 to form a Cr2N type chromium nitride coating layer of 10-50mum thickness on at least the peripheral surface of the piston ring. Surface treatment ensuring high hardness and superior durability can be carried out.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for surface treatment of piston rings with excellent wear resistance, and more particularly, to a method for surface treatment of piston rings with excellent wear resistance. The present invention relates to a piston ring nitriding method with improved durability and excellent durability.

(Prior Art and Problems) In recent years, as the performance of internal combustion engines has improved, increasingly severe conditions have been imposed on each functional component, and there has been a strong demand for extending the life of internal combustion engines. Piston rings are also exposed to harsh environments such as high rotation, high temperature, and high surface pressure more than ever before, and there is a need to improve their durability. Abrasion-resistant treatments such as chrome plating and nitriding are applied.

With these surface treatments, conventional piston rings with a chrome plating layer no longer have sufficient wear resistance, and nitriding has excellent wear resistance, making it the top choice used under harsh operating conditions. It has attracted attention as a surface treatment for rings, and has recently been used more frequently.

However, the nitriding treatment conventionally applied to piston rings is carried out at a high temperature (approximately 570° C.), which tends to cause deformation of the piston rings and increases manufacturing costs.

Furthermore, in the case of conventional nitriding treatment, the nitrided layer effective for wear resistance has a thickness of about 10 μm at most, and therefore has the disadvantage of short durability. Furthermore, compared to chromium plating, which is currently widely used, it does not have sufficient anti-seizure properties, and there is a problem in that it is more likely to cause seizing.

(Means for Solving the Problems) The present invention has been made by focusing on the problems of the conventional nitriding process described above, and provides sufficient wear resistance and seizure resistance even under severe usage conditions. It is an object of the present invention to provide a method for nitriding the surface of a piston ring with good durability.

The present invention utilizes a reactive ion plating method in which an evaporated substance is evaporated in an atmosphere containing a reactive gas to form a coating layer made of a reaction product of the reactive gas and the evaporated substance on the surface of an object to be treated, An internal combustion engine characterized in that a coating layer made of Cr2N type chromium nitride with a thickness of 10 to 50 μm is formed on at least the outer peripheral sliding surface of a piston ring by employing nitrogen gas as a reactive gas and chromium as an evaporative substance. This is a method for surface treatment of piston rings for use in industrial applications.

Here, the reactive ion plating method is to evaporate the evaporated substance in a reaction gas atmosphere, ionize it in the gas phase, and generate a reaction product between the reaction gas and ions of the evaporated substance on the substrate surface that is negatively biased. This is a known surface treatment method for forming a coating layer, which is characterized by forming a dense coating layer at low temperatures.

In the present invention, the surface coating layer formed on the sliding surface of the piston ring uses nitrogen gas as the atmospheric gas.

This is a Cr2N type chromium nitride nitride layer formed by a reactive ion plating method using chromium as the evaporation material.

When chromium is used as an evaporation material, the vapor pressure of chromium is higher than that of Ti, which has been conventionally used as an evaporation material in reactive ion plating, and therefore the formation rate of the chromium nitride layer of the present invention is high. This is a practical method for surface treatment of dovetail piston rings.

In addition, the thickness of the nitride layer formed on the sliding surface of the conventional nitrided piston ring was limited to 10 μm at most, which caused problems in terms of durability, but in the case of the present invention, the piston ring The thickness of the chromium nitride coating layer formed on the sliding surface of the piston ring can be increased to 10 μm or more, and therefore a piston ring with sufficient durability can be obtained.

On the other hand, if the thickness of the nitrided coating layer is increased beyond 50 μm, the coating layer is likely to peel off and the quality will be excessive.
It was set as m.

In the present invention, in order to improve the wear resistance of the upper and lower surfaces of the piston ring, the above-mentioned nitride coating layer may be formed on the upper and lower surfaces of the piston ring, but the thickness of the nitride layer on the upper and lower surfaces of the piston ring may be 10 μm or less. It is valid.

(Example) The nitriding method according to the present invention will be explained in detail based on an example.

Figure 3 shows an overview of the reactive ion plating equipment used. In this equipment, H is used as the evaporation energy source.
Although a CD-type electron gun was used, a normal electron gun may be used in an apparatus having an ionization mechanism that utilizes high-frequency discharge.

The piston ring holder 4 housed in the container 3 is rotated by a rotating device (not shown). The piston ring base material 1 held by the holder 4 is heated and kept warm at about 400° C. by the heater 5 located above it. A water-cooled copper crucible 6 is disposed below the screw 1 to ring base material 1, and the crucible 6 contains chromium 7, which becomes an evaporated substance. Gas introduction '1iF to introduce atmospheric gas into the side wall of the container 3
9 and an HCD gun 10 are provided, and a converging coil 8 for converging the plasma beam from the HCD gun 10 onto the evaporated material 7 is provided. Incidentally, the container 3 is connected to a vacuum pump (not shown) so that the pressure can be reduced.

Using the above apparatus, a plurality of top rings made of alloy steel SU8 440C with an outer diameter of 80 mm, a width of 1.5 mm, and a thickness of 3.5 mm are heated to approximately 400°C as the base material 1, and the gas introduction pipe 9 is Container 3 with argon gas introduced
After sputter cleaning for 10 minutes using the piston ring base material 1 as a cathode at a pressure of I x 10-1 torr, the chromium 7 contained in the crucible 6 is evaporated by a plasma beam, and the chromium 7 is evaporated from the gas introduction pipe 9. Evaporated gas is introduced into the container 3, and the inside of the container 3 is
Coating was carried out for 40 minutes at orr. here,
The plasma beam output was about 50 OA, and a bias voltage of -30 V was applied to the piston ring base material 1.

The following investigations and tests were conducted on the obtained coating layer 2 shown in FIG.

(1) Investigation of the constituent structure of the coating layer by X-ray analysis (2) Thickness and hardness of the coating layer (3) Wear resistance test (4) Seizure resistance test The results of the investigation and test are as follows. Ta.

(1) Investigation results of the structure of the coating layer by X-ray analysis The structure of the coating layer formed on the outer peripheral surface of the piston ring base material was investigated by It was confirmed that it was a nitride.

(2) Thickness and hardness of the coating layer The thickness of the coating layer made of Cr2N type chromium nitride of the product of the present invention was 35 μm, which was able to be formed thicker than conventional nitriding treatment.

The hardness of the inventive product is HMV1500-2000, which is approximately twice as high as the HMV700-1100 of conventional nitrided products, confirming that it is a highly durable piston ring. It was done.

(3) Wear resistance test The wear resistance test was performed by finishing the above piston ring, installing the resulting top ring in an actual engine, and conducting a bench test to evaluate the wear resistance and seizure resistance. Ta.

The test conditions are described below.

Engine used 4 cylinders 1800cc Cylinder inner diameter 80mm x stroke 89mm Operating conditions rotation speed 600Or, p, m 4/41oad fuel
For comparison purposes, similar tests were conducted on piston rings that had been subjected to conventional chromium plating treatment and piston rings that had been nitrided using the conventional method.

The test results are shown in Figure 2.

As is clear from Figure 2, the amount of wear of the piston ring of the present invention is 7 μm, and that of the comparative chrome-plated ring is 56 μm.
It is also 1/3 less than the conventional nitrided ring's 21μm, and the amount of wear on the mating cylinder is 2μm, which is about the same as the comparative amount of chrome plating. It was confirmed that the wear resistance was significantly superior, being 4 μm, half that of conventional nitrided rings.

(4) Seizure resistance test Using a test piece made of alloy steel 5US440C and measuring 5 mm in length x 5 mm in width x 10 mm in height, a test piece was prepared in which a nitrided layer of the present invention with a thickness of 35 μm was formed on the 5 mm square end face. Then, a seizure resistance test was conducted using an ultra-high pressure abrasion tester.

As a comparative example, a 5 mm square end face of a test piece was coated with a thickness of 5 mm.
A similar test was conducted using a test piece in which a hard chromium plating layer of 0 μm and a nitrided layer with a thickness of 8 μm was formed by conventional nitriding treatment.

The equipment and test conditions of the ultra-high pressure abrasion tester used in this test are as follows.

The main parts of the test device are schematically shown in FIG. 4 and FIG. 5, which is a sectional view taken along the line A-A in FIG.
Polished disc 12 (gold hand material) with a thickness of 10 mm
Lubricating oil is supplied to the center of the housing from the back side through the oil supply hole 13. A pressing force P is applied to the stator holder 11 by a hydraulic device (not shown) at a predetermined pressure toward the right in the figure. A rotor 14 faces the disk 12.
1, which is rotated at a predetermined speed by a drive device (not shown). A test piece holder 15 attached to the end face of the rotor 14 with respect to the disc 12 has a 5ml 11 square end face on which a surface treatment layer is formed.
0 can be removed at equal intervals on a concentric circle, and the disc 12
It is attached so that it can slide freely.

In such a device, a predetermined pressing force P is applied to the stator holder 11 so that the disk 12 and the test piece 20 come into contact with each other with a predetermined surface pressure, and a predetermined amount of oil is supplied to the sliding surface from the oil filling hole 13. The rotor 14 is rotated while being refueled at a high speed.

The pressure acting on the stator holder 11 is increased stepwise at regular intervals, and the test piece 2 is rotated by the rotation of the rotor 14.
0 and the other disc 12 causes the stator holder 1 to
1 is applied to the load cell 17 via the spindle 16, and its change is read by the dynamic strain meter 18 and recorded in the recorder 19. It is assumed that seizure has occurred when the torque T suddenly increases, and the quality of the seizure resistance is determined based on the contact surface pressure at this time.

The test conditions are as follows.

Friction speed: 5 m/sec Mating material: Cast iron FC25 for cylinder liner Contact surface pressure:
After smoothing out at 20 kg/am2, increase the pressure by 10 kg/cm" until seizing occurs and hold each surface pressure for 3 minutes. Lubricating oil: Motor oil #30 Oil temperature 80°C Supply amount 400 cc/win Test results, present invention Seizing occurred at a contact surface pressure of 150 kg/cm2 for the product, but the seizure resistance was higher than that of a comparative chrome-plated product of 110 kg/cm2, and even for a nitrided product at a contact pressure of 130 kg/cm2. It was confirmed that the properties were excellent.

(Effect) Using the reactive ion plating method according to the present invention,
By using nitrogen gas as the reactive gas and chromium as the evaporative substance, a coating layer made of Cr2N type chromium nitride is formed on at least the outer sliding surface of the piston ring, resulting in excellent wear resistance and seizure resistance. The industrial effect is remarkable in that it has become possible to form a thick coating layer and a piston rig with good durability has been obtained.

[Brief explanation of the drawing]

Fig. 1 A sectional view showing an example of a piston ring of the present invention Fig. 2 A graph showing the results of a wear resistance test Fig. 3 An explanatory view showing an example of a reactive ion plating device Fig. 4 Ultra-high pressure wear test Partially fractured explanatory diagram Figure 5 Cross-sectional view taken along the line A-A in Figure 4 1: Piston ring base material 2: Covering layer 3: Container
4: Ring holder 5: Heater 6: Water-cooled copper crucible
7: Evaporated substance 9: Gas introduction pipe 10:
HOD gun 11: Stator holder

Claims (1)

[Claims] By the reactive ion plating method, the evaporated substance is evaporated in an atmosphere containing a reactive gas, and a coating layer made of a reaction product of the reactive gas and the evaporated substance is formed on the surface of the workpiece.
A piston characterized in that a coating layer made of Cr_2N type chromium nitride with a thickness of 10 to 50 μm is formed on at least the outer peripheral sliding surface of a piston ring by using nitrogen gas as a reactive gas and chromium as an evaporative substance. Ring surface treatment method.