JPH01159449A - Piston ring with compound nitriding layer - Google Patents

Abstract

PURPOSE:To improve both of abrasion resistance and anti-seizure by forming a compound coating layer consisting of a first coating phase composed of Cr2N type chromium nitride and a second coating phase composed of CrN type chromium nitride in making the best use of a reactive ion plating process. CONSTITUTION:When a compound nitriding layer 2 is formed on at least a peripheral sliding surface of a piston ring 1, evaporation material is evaporated in a reaction gas atmosphere, ionized in a vapor phase state, and a reactive ion plating process made so as to form a coating layer, consisting of a reaction product between a reaction gas and an evaporation ion, on a substrate surface formed into negative bias is adopted, using nitrogen gas as the reaction gas and chromium as the evaporation material. With this constitution, the compound coating layer 2 consisting of a first coating phase composed of Cr2N type chromium nitride and a second coating phase composed of CrN type chromium nitride, is formed on a peripheral sliding surface of the piston ring 1.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a piston ring with excellent wear resistance, and more particularly, to a piston ring with excellent wear resistance and seizure resistance that has a composite nitrided layer formed by ion plating. This invention relates to a piston ring with improved 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 harsher environments such as high rotation, high temperature, and high surface pressure than ever before, and there is a need for improved durability. Abrasion-resistant treatments such as 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 microns 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. have

It is an object of the present invention to provide a piston ring having a composite nitride layer 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, By employing nitrogen gas as a reactive gas and chromium as an evaporative substance, a first coating phase made of CrN type chromium nitride with a thickness of 10 to 50 μm and further CrN type nitride are formed on at least the outer peripheral sliding surface of the piston ring. This piston ring for an internal combustion engine is characterized by having a composite coating layer consisting of a second coating phase made of chromium.

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 is a first coating layer of Cr2N type chromium nitride, which is formed by a reactive ion plating method using nitrogen gas as the atmospheric gas and chromium as the evaporated substance. And further Cr
This is a composite nitride layer consisting of a second coating phase of N-type chromium nitride.

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 with the present invention, the sliding surface of the piston ring The thickness of the composite chromium nitride coating layer formed on the dynamic surface can be increased to 10 μm or more, and therefore a piston ring with sufficient durability can be obtained.

On the other hand, increasing the thickness of the composite nitride coating layer to more than 50 μm tends to cause peeling of the coating layer and result in excessive quality, so in the present invention, the thickness range of the composite coating layer is
~50 μm.

In the present invention, in order to improve the wear resistance of the upper and lower surfaces of the piston ring, the above-mentioned composite nitride coating layer can be formed on the upper and lower surfaces as well, but the thickness of the composite nitride layer on the upper and lower surfaces of the piston ring is 10 μm. The following is also valid.

(Example) A piston ring having a composite nitride layer according to the present invention will be described in detail based on an example.

Figure 3 shows an outline of the reactive ion plating apparatus used. In this device, 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 piston ring base material 1.
Chromium 7, which becomes an evaporative substance, is stored inside. On the side wall of the container 3 are a gas introduction pipe 9 for introducing atmospheric gas and an HC.
A D gun 10 is provided, and a converging coil 8 for converging the plasma beam from the HCD gun 10 onto the evaporated substance 7 is provided.6 The container 3 is connected to a vacuum pump (not shown) so that it can be depressurized.

Using the above-mentioned device, the base material 1 made of 5-alloy steel SUS 440G with an outer diameter of 80 mm x @ 1.5 mm x thickness of 3.5 mm is heated to about 400°C, and the gas introduction pipe 9 is heated to about 400°C. After introducing argon gas and setting the pressure in the container 3 to I x 10-1 torr and performing sputter cleaning for 10 minutes using the piston ring base material 1 as a cathode, the chromium 7 housed in the crucible 6 is removed by a plasma beam. The evaporated gas is introduced into the container 3 through the gas introduction pipe 9, and the inside of the container 3 is
rr for 40 minutes and coated with Cr2N.
A nitride layer consisting of CrN-type chromium nitride and CrN-type chromium nitride was formed.

Here, the plasma beam output was set to about 500 A, and a bias voltage of -30 V was applied to the piston ring base material 1.

The obtained composite coating layer shown in Fig. 1 was investigated and tested in this period.

(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 result of the structure of the coating layer by X-ray analysis The structure structure of the coating layer 2 formed on the outer circumferential surface of the piston ring base material 1 was investigated by X-ray analysis, and it was found that the coating layer is Cr2N
It was confirmed that this was a chromium nitride consisting of a first coating phase made of CrN-type chromium nitride and a second coating phase made of CrN-type chromium nitride.

(2) Thickness and Hardness of Coating Layer The thickness of the composite coating layer of the present invention was 40 μm, which was so thick that it could not be obtained by conventional nitriding treatment.

The hardness of the composite coating layer of the present invention is HMV1600-2000
and conventional nitrided piston ring HMV700-11
The hardness was approximately twice as high as that of 00, and it was confirmed that the piston ring had good durability.

(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. 'Test conditions are described below.

Engine used 4 cylinders 1800cc Cylinder inner diameter 80mm x stroke 89m + * Operating conditions rotation speed 600 Or, p, m 4/4 Load 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 Fig. 2, the amount of wear of the piston ring of the present invention is 4 μm, and that of the comparative chrome-plated ring is 50 μm.
It is also 1/4 less than the conventional nitrided ring's 18μI, and the amount of wear on the mating cylinder is 2μ, which is about the same as the chrome plating of the comparative product. It was confirmed that the wear resistance was 4 μm, half that of the conventional nitrided ring.

(4) Seizing resistance test ゛A test piece made of alloy steel 5US440C measuring 5 mm long x 5 mm wide x 10 III 11 high was used, and a 35 μm thick composite nitrided layer according to the present invention was formed on the square end face of 5 mm + corner. was prepared and subjected to a seizure resistance test using an ultra-high pressure abrasion tester.

As a comparative example, a similar test was conducted using a test piece in which a 50 μm thick hard chrome plating layer was formed on the 5++m square end face of the test piece and an 8 μl thick nitrided layer 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 (plywood) 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 hydraulic device (not shown) applies a pressing force P to the stator holder 11 with a predetermined pressure toward the right in the figure.
It is designed to rotate at a predetermined speed by a drive device (not shown). A test piece holder 15 attached to the end face of the rotor 14 relative to the disk 12 has a 5 mm square end face formed with a surface treatment layer as a sliding surface, and four test pieces 20 can be removed at equal intervals on a concentric circle. and is slidably attached to the disc 12.

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 leveling at 20 kg/cm", increase the pressure by 10 kg/cm" increments 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, book The invented product showed seizure resistance at 150 kg/c+a", but the seizure resistance was higher than that of the conventional chrome-plated product for comparison, which was 110 kg/cm", and the seizure resistance was higher than that of the nitrided product at 130 kg/7 cm. was confirmed to be excellent.

(Effect) Using the reactive ion plating method according to the present invention,
By employing nitrogen gas as a reactive gas and chromium as an evaporative substance, a first coating phase made of Cr2N type chromium nitride and a second coating phase made of CrN type chromium nitride are formed on at least the outer peripheral sliding surface of the piston ring. By forming a composite coating layer consisting of the following, a thick coating layer with excellent wear resistance and seizure resistance was formed. The industrial effect of obtaining a piston rig with good durability is remarkable.

[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 Figure 5: Partial crushing diagram of the device
Cross-sectional view taken along the line A-A in Fig. 4 1: Piston ring base material 2: Composite coating layer 3: Container 4: Ring holder 5: Heater 6: Water-cooled copper crucible 7: Evaporated substance 9: Gas introduction pipe 10: HCD Gun 11: Stator holder 12: Disk (mate material) 14: Rotor
15: Test piece holder 17: Load cell 18: Dynamic strain meter 20: Test piece

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.
Using nitrogen gas as a reactive gas and chromium as an evaporative substance, a first coating phase made of Cr_2N type chromium nitride with a thickness of 10 to 50 μm and further a CrN type chromium nitride are applied to at least the outer peripheral sliding surface of the piston ring. A piston ring characterized in that a composite nitride layer made of a second coating phase is formed.