JPS62120471A - Piston ring - Google Patents

Abstract

PURPOSE:To obtain piston ring superior in wear resistance and seizure resistance, by forming a nitriding treated layer at upper, under and inner peripheral surfaces of a piston ring base body, and forming a composite layer made of uniform and fine mixed phase of metallic chromium and chromium nitride at outer peripheral surface. CONSTITUTION:The nitriding treated layers 4, 5 are formed by conventional method at upper, under sides and inner peripheral surfaces excluding an outer peripheral sliding surface 2 of the piston ring base body 1 made of cast iron or steel. On the other hand, the composite layer 6 made of fine and uniform mixed phase of metallic chromium and chromium nitride is formed on the body 1 at the outer peripheral sliding surface 2. The layer 6 is formed by reactive ion plating method in which metallic chromium is sputtered as target material in reduced pressure atmosphere under existence of gaseous nitrogen, and has high hardness and good adhesive property. In this way, piston ring for internal engine having good endurance and exhibiting sufficient resistance characteristics for wear and baking even under severe using condition is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a piston ring, and more particularly to a piston ring for an internal combustion engine with improved anti-seizure characteristics and anti-wear characteristics.

[Conventional technology and problems]

Piston rings used in reciprocating internal combustion engines require high wear resistance properties. Therefore, for the purpose of improving the wear resistance characteristics of piston rings, piston rings having a hard chromium plating layer formed on the sliding surfaces have been widely used as piston rings for internal combustion engines.

Incidentally, in recent years, internal combustion engines have become faster and more powerful, and there are also problems such as corrosion and wear due to the use of high-lead gasoline.

The usage conditions for piston rings are becoming increasingly harsh, and piston rings with conventional chrome plating layers may not have sufficient wear and seizure resistance. It was desired.

Therefore, efforts have been made to further improve the wear and seizure resistance properties of piston rings. Japanese Unexamined Patent Publication 1987-
57868 and JP-A-57-65837), a nitrided layer is formed on the inner and outer peripheries and upper and lower side surfaces of the piston ring, and a metal nitride (T) is further formed on the nitrided layer on the outer peripheral surface.
Piston ring with an ion brating layer formed of iN or CrN (Utility Model No. 59-12615)
No. 9) has been proposed.

Metal nitrides and carbides are materials that exhibit excellent wear resistance, but they themselves are extremely hard and lack flexibility;
Because the coefficient of thermal expansion is significantly smaller than that of metals,
Poor adhesion to metal base material.

Therefore, when a metal nitride layer or carbide layer is formed on the sliding surface of the piston ring, separation from the piston ring base material is likely to occur, especially when the nitrided layer formed on the surface of the ring base material When this kind of nitride layer or carbide layer is further formed on top of the nitride layer, there is a problem that adhesion is insufficient because the nitrided layer is porous, and the nitride layer or carbide layer is likely to peel off. .

Furthermore, when metal nitrides and metal carbides are formed by the ion blasting method, the rate of film formation is slow.

Since it takes a long time to form a coating layer of sufficient thickness, there are production delays and it is not practical.)

[Purpose of the invention]

The present invention has been made for the purpose of solving the above-mentioned problems and providing a highly durable piston ring for an internal combustion engine that exhibits sufficient wear and seizure resistance even under severe usage conditions.

[Structure and effects of the invention]

In this invention, a nitrided layer is formed on the upper and lower side surfaces and the inner circumferential surface of a cast iron or steel piston ring base excluding the outer circumferential surface,
The above object is achieved by providing a piston ring in which a composite layer consisting of a uniform fine mixed phase of metallic chromium and chromium nitride is formed on the outer circumferential base of the piston ring. In FIG. 1, which shows a cross section of an embodiment of a piston ring for an internal combustion engine according to the present invention, the upper and lower sides of a piston ring base 1 made of cast iron or steel, except for the outer sliding surface side 2, are treated with nitriding by a conventional method. Layer 4.5 is formed.

On the other hand, on the outer peripheral sliding surface side, a composite layer 6 made of a fine and uniform mixed phase of metallic chromium and chromium nitride is formed on the piston ring base material. In the present invention, the composite layer phase 6 consisting of a mixed phase of metallic chromium and chromium nitride is formed by a reactive ion blasting method in which sputtering is performed using metallic chromium as a target material in a reduced pressure atmosphere in the presence of nitrogen gas. Ru.

The composite calendar date of the present invention has a high hardness (preferably hardness HmV 1
000 or more), but because it is a fine and uniform mixed phase of metallic chromium and chromium nitride, it is not as fragile as chromium nitride alone, and its thermal expansion coefficient is close to that of metallic chromium. has been done.

Therefore, the composite layer 6 has good adhesion to the piston ring base material and does not peel off.

Further, in the piston ring of the present invention, the nitrided layer 4.5 is formed on the upper and lower side surfaces and the inner peripheral surface to impart wear resistance to the side surfaces, and the composite layer 6 on the outer peripheral sliding surface
is formed on a piston ring base plate without a nitrided layer. Therefore, due to the material properties of the composite layer, that is, it is not brittle and has an appropriate coefficient of thermal expansion, the problem of peeling occurs in conventional piston rings in which a metal nitride layer is formed on a nitrided layer. is effectively prevented.

The composite layer of metallic chromium and chromium nitride formed on the outer peripheral surface of the piston ring base of the present invention can be formed by a PVD method, preferably a reactive ion blating method in which metallic chromium is evaporated in a reduced pressure nitrogen gas atmosphere. It is formed by converting a part of the metallic chromium into chromium nitride during the evaporation process of metallic chromium to form a fine and uniform mixed phase of a metallic chromium phase and a chromium nitride phase.

In the present invention, the reason why chromium and its nitride are used as the components constituting the composite layer 6 is that the chromium phase formed on the surface of the ring base material by the reactive ion blasting method has good adhesion to the base material. In addition, its thermal expansion coefficient is close to that of the base material, and is therefore extremely suitable for preventing the composite layer 6 from peeling off during use of the piston ring. Another reason why chromium is particularly adopted as a component of the composite layer 6 in the present invention is that the evaporation rate of metallic chromium by the ion blating method is higher than that of other metals and is extremely effective from the viewpoint of productivity. It depends.

The composite layer 6 of the piston ring of the present invention can be formed by, for example, setting the object to be treated in a container of a reactive ion blating device, evacuating the inside of the container, and applying a pressure of 5X10-'Torr.
The object to be treated is heated to a predetermined temperature, and then argon gas is introduced into the container and
The surface of the object to be processed is cleaned by bombardment at a pressure of approximately 1.5 Torr, then nitrogen gas is introduced into the container to achieve a predetermined nitrogen gas partial pressure, and metallic chromium is evaporated using an HCD type electron gun as an evaporating agent to perform vapor deposition processing. It is formed by Here, it is desirable that the temperature of the workpiece during treatment be around 400°C, and if the nitrogen gas partial pressure is too high, a mixed layer where metal chromium and chromium nitride coexist will form. Therefore, it is desirable to set the IX to about 10-3 Torr or less. Table 1 shows the temperature of the object to be treated as 400°C.
The results of examining the structural structure and hardness of coating layers formed by reactive ion blating at various nitrogen gas partial pressures are shown. Note that the investigation of the constituent tissues was carried out by X-ray analysis. The results of the X-ray analysis are shown in Figure 2.

From Table 1 and Figure 2, as the nitrogen gas partial pressure increases,
It can be seen that the metallic chromium in the resulting coating layer disappears and becomes chromium nitride alone, resulting in increased hardness.

As described above, the piston ring of the present invention is provided with wear resistance by the nitrided layer on the upper and lower side surfaces of the piston ring,
On the outer sliding surface side, a composite layer consisting of a finely uniform mixed phase of metallic chromium and chromium nitride is formed on the piston ring base material, resulting in excellent wear resistance and seizure resistance, and good durability. In order to improve the durability of the engine,
It shows a remarkable effect.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a piston ring of the present invention, and FIG. 2 is an X-ray analysis chart showing the structure of the coating layer of each sample. In the diagram: 1. ,, piston ring base 209. Piston ring base outer peripheral surface 498. Nitriding layer 513. Nitriding layer

Claims (1)

[Claims] A nitriding layer is formed on the top, bottom, and inner surfaces of the cast iron or steel piston ring base excluding the outer peripheral surface, and a composite layer consisting of a uniform fine mixed phase of metallic chromium and chromium nitride is formed on the outer peripheral surface of the piston ring base. A piston ring for an internal combustion engine, characterized in that a layer is formed.