JPH0827558A - Wear resistant thermally sprayed layer, its formation and sliding member coated with the wear resistant thermally sprayed layer - Google Patents

Abstract

PURPOSE:To form a thermally sprayed layer excellent in wear resistance and seizing resistance. CONSTITUTION:The wear resistant thermally sprayed layer is formed on the inner circumferential face of a cylinder liner made of steel. This thermally sprayed layer is constituted of steel contg. 0.25 to 2.2% C and <=13.0% of one or >=two kinds selected from among Cr, Mo, W and V, furthermore, in which unmelted grains are dispersed into the matrix by 10 to 50% area ratio, and moerover, the hardness of the unmelted grains and matrix is different, and that of the higher one is regulated to >=400HV.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an abrasion resistant sprayed layer,
It is effective to cover a sliding member such as a cylinder liner.

[0002]

2. Description of the Related Art In order to reduce the size and weight of an engine,
Cylinder liners made of thin steel are being considered. JP-A-58-27860 proposes to combine a cylinder liner made of steel having a specified composition and a piston ring made of a material having a specified composition, and subject one of them to a soft nitriding treatment. However, this cylinder liner is inferior in seizure resistance to a cast iron cylinder liner.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
-350106 proposes to combine a PVD-treated piston ring with a steel cylinder liner of a specified composition, and further, in Japanese Patent Application No. 6-56746, PVD.
A combination of a treated piston ring and a cylinder liner sprayed with a steel-based material with a specified composition was proposed.

However, in both cases, T is used as a sliding mating material.
It is necessary to combine with a piston ring that has been subjected to PVD treatment such as iN or CrN, and sliding mating materials have been limited.

Although it has been proposed to coat the sliding surface with a thermal spray layer in order to improve sliding characteristics, conventionally proposed abrasion resistant thermal spray coating materials such as ceramics, molybdenum, Ferrochrome, nickel-based self-fluxing alloy and the like are both expensive and are not suitable as a surface treatment for improving the wear resistance and seizure resistance of a steel cylinder liner.

An object of the present invention is to provide a sprayed layer having excellent wear resistance and seizure resistance, a method for forming the same, and a sliding member coated with the sprayed layer.

[0007]

The composition of the wear resistant sprayed layer of the present invention is such that the weight% of C0.25 to 2.2%, Cr, M.
It is made of steel containing 13.0% or less of 1 or 2 or more of o, W, and V (in the case of 2 or more, it is the total value), and the area ratio of unmelted particles in the matrix is 10 to 50%. In addition, the hardness of the unmelted particles is different from that of the matrix, and the higher hardness is HV (Vickers hardness) of 400 or more.

The hardness difference between the unmelted particles and the matrix is H
It is preferably V30 or more. More preferably HV1
00 or more and HV250 or less are desirable. The hardness of the unmelted particles and the matrix with the lower hardness is HV30.
0 or more is desirable.

The particle size of the unmelted particles is preferably in the range of 10 to 100 μm.

The method for forming the abrasion resistant sprayed layer is to spray a mixed powder consisting of steel powder having a small particle size intended to be melted and steel powder having a large particle size intended to be dispersed in an unmelted state. It is characterized by forming a sprayed layer in which unmelted particles are dispersed in a matrix.

The mixed powder is composed of powder materials having the same composition or two or more kinds of powder materials having different hardness after thermal spraying.

When powder materials having the same composition are used, the hardness of the unmelted particles becomes higher than the hardness of the matrix.

When two or more kinds of powder materials having different hardness after thermal spraying are used, if the powder material having a larger particle size to be left as unmelted particles is the powder material having higher hardness after thermal spraying, If the hardness of the unmelted particles can be made higher than the hardness of the matrix, and the powder material with the larger particle size left as unmelted particles is the powder material with the lower hardness after thermal spraying, the hardness of the unmelted particles Can be lower than hardness.

By covering the inner peripheral surface of the cylinder liner made of steel or aluminum alloy with the above-mentioned wear resistant sprayed layer, it is possible to provide a cylinder liner having high strength, thin wall thickness and excellent sliding characteristics.

[0015]

In the abrasion resistant sprayed layer of the present invention, unmelted particles having a hardness different from the hardness of the matrix are present in the matrix. Therefore, a concave portion is formed in a portion having low hardness during sliding, and the concave portion functions as an oil sump, so that the sliding characteristic is excellent.

Since there is a difference in hardness between the matrix and the unmelted particles, even when sliding for a long period of time, a concave portion is always formed in a portion having a low hardness, so that good sliding characteristics are maintained for a long period of time. It

When the unmelted particles have a hardness higher than that of the matrix, the recesses are formed in the matrix, and therefore the recesses tend to be continuously formed. When the unmelted particles have a hardness lower than that of the matrix. Since the concave portion is formed in the unmelted particle portion, the concave portion is formed discontinuously. Therefore, a more suitable sliding surface can be provided according to the sliding conditions, the mating material, and the like.

If the higher hardness of the unmelted particles and the matrix is less than HV400, the seizure resistance is lower than that of the conventional cast iron cylinder liner. Therefore, the higher hardness of the unmelted particles and the matrix is HV40.
0 or more is required. The upper limit is HV7 from the point of attacking opponents
00 is preferable. The higher hardness of the unmelted particles and the matrix is more preferably HV500 or higher, HV6 or higher.
50 or less is desirable.

The area ratio of unmelted particles is 10 in the microscopic structure.
If it is less than%, the seizure resistance is lower than that of the conventional cast iron cylinder liner. On the other hand, if it exceeds 50%, the adhesion of the unmelted particles is deteriorated and the abrasion resistance is deteriorated. Therefore, the area ratio of the unmelted particles needs to be in the range of 10 to 50%. More preferably 25% or more, 40%
The following is desirable.

If the particle size of the unmelted particles is less than 10 μm, it becomes difficult to control the area ratio of the unmelted particles during the thermal spraying, and if it exceeds 100 μm, the thermal spraying becomes difficult. Therefore, the particle size of the unmelted particles is 10 to 100 μm.
Is preferred. More preferably, it is 30 μm or more and 80 μm or less.

The C content is preferably 0.25% or more in terms of wear resistance, and 2.2% or less in terms of toughness. More preferably, the content is 0.4% or more and 1.5% or less.

The content of the carbide-forming elements (Cr, Mo, W, V) is preferably 13.0% or less in terms of seizure resistance. The lower limit is preferably 0.6% from the viewpoint of wear resistance. The more preferable content of the carbide-forming element (Cr, Mo, W, V) is 1.0% or more and 7% or less.

[0023]

EXAMPLE A seizure test and a wear test were conducted using a reciprocating wear tester which is empirically known to reproduce the sliding phenomenon between a cylinder liner and a piston ring, and the wear resistance of the present invention was evaluated. The sprayed layer was evaluated.

Details of the reciprocating wear tester and the test conditions were as follows.

(1) Reciprocating abrasion tester FIG. 5 shows an outline of the reciprocating abrasion tester. In FIG.
10 is a plate-shaped test piece, which is placed and fixed on the test table 11,
The tip of the pin-shaped test piece 12 is pressed against the upper surface of the test piece 10 by the hydraulic unit 13. In this state, test bench 1
A wear test is carried out by reciprocating 1 in the horizontal plane by the crank mechanism 14. Reference numeral 15 is an indicator for hydraulic load, 16 is a load cell for detecting frictional force, and 17 is a recorder for recording the detected frictional force.

(2) Sliding mating material (pin-shaped test piece 12) The material is carbon tool steel (JIS SK5) and the tip has a diameter of 18
After spherical processing to mm, hard Cr plating was applied and polishing finish was performed. The hard Cr plating has a plating thickness of 100 μm and a hardness of HV900.

(3) Test piece (plate-shaped test piece 10) The material is carbon steel (JIS S45C) and the dimensions are 17 × 14.
A steel material having various compositions was sprayed on one surface (sliding surface) of 70 (mm) and then polished.

(4) Thermal spraying method A test piece was fixed on the inner peripheral surface of a cylindrical jig having an inner diameter of 108 mm, the jig rotation speed was 300 rpm, and the thermal spray gun distance was 40.
mm, spray gun stroke: 190 mm, reciprocating speed:
High speed gas spraying method (HVOF) under the condition of 500 mm / min.
Thermal spraying method). Table 5 shows the details of the thermal spraying conditions.

(5) Seizure test A seizure test was conducted by using a lubricant having a viscosity equivalent to light oil and increasing the load stepwise at a rate of 2 kg per minute with a reciprocating abrasion tester.

(6) Abrasion test A lubricant having a viscosity equivalent to light oil was used, and the condition for the smoothing period was 2
kg (load) x 100 cpm (speed) x 5 min (time), test condition: 10 kg (load) x 600 cp
The amount of wear was measured after testing with a reciprocating wear tester at m (speed) × 60 min (hours).

(7) Measurement of Area Ratio of Unmelted Particles After spraying, the surface was polished and the area ratio of unmelted particles was measured by an image analyzer.

[Seizure Test] A seizure test was performed using various test pieces shown in Tables 1 and 2. Example 1
In Comparative Examples 2 and 3, after thermal spraying, various heat treatments were performed to adjust the hardness of the unmelted particles, and the effect of the hardness of the unmelted particles on the seizure resistance was examined.

In Table 1, the column of particle size distribution of thermal spray powder,
The meanings of the symbols in the heat treatment column and the thermal spraying column are shown in Table 3, Table 4 and Table 5, respectively.

Table 2 also shows the seizure loads obtained. According to this, when the hardness of the unmelted particles was HV 400 or more, a seizure load higher than that of the cast iron for cylinder liner of Comparative Example 1 was obtained.

Further, the influence of the area ratio of the unmelted particles on the seizure load was investigated. As a result, when the area ratio of the unmelted particles was 10 to 50%, a seizure load higher than the seizure load of the cast iron for cylinder liner of Comparative Example 1 was obtained.

[0036]

(Note 1) Comparative Example 1 is cast iron for a cylinder liner, and other components are P0.2%, S0.03%, Cu
It is 0.4%. Hardness is HRB (Rockwell hardness) 9
It is 6.

[0038]

[0039]

[0040]

[0041]

[Abrasion Test] An abrasion test was conducted using various test pieces shown in Tables 6 and 7. The results are shown in FIG.

In Examples 9 to 17, the composition of the powder material intended to be melted and the composition of the powder material intended to be dispersed in the unmelted state were the same.

In Example 18, the composition of the powder material intended to be melted and the composition of the powder material intended to be dispersed while being unmelted were different. In Example 18, the hardness of the matrix is unmelted by making the C content of the powder material having a large particle diameter to be unmelted particles smaller than the C content of the powder material having a small particle diameter intended to be melted. It was made higher than the hardness of the particles. By the way, if the C content of the powder material having a large particle size to be the unmelted particles is made larger than the C content of the powder material having a small particle size intended to be melted, the hardness of the unmelted particles becomes higher than the hardness of the matrix. A high sprayed layer can be formed.

As shown in the test results of FIG. 2, in each of the examples of the present invention, both the wear amount of itself and the wear amount of the mating material were lower than those of the cast iron for cylinder liner of Comparative Example 5.

[0046]

(Note 1) Example 18 is a mixture of the upper composition powder and the lower composition powder in the following mixing ratio. Upper composition powder: Lower composition powder = 7: 3

(Note 2) Comparative Example 5 is cast iron for cylinder liner, and other components are P0.2%, S0.03%, Cu
It is 0.4%. Hardness is HRB (Rockwell hardness) 9
It is 6.

(Note 3) The meanings of the symbols in the particle size distribution column of the sprayed powder and the spraying condition column are shown in Table 3 and Table 5, respectively.

[0050]

As is clear from the seizure test and wear test described above, the sprayed layer of the present invention shows sliding characteristics superior to those of the conventional cast iron for cylinder liner, and is excellent as a sprayed layer for cylinder liner. It can exhibit dynamic characteristics.

FIG. 1 is an example of a micrograph of a surface parallel to the sprayed layer in the sprayed layer of the present invention. The surface portion of the atomized powder may be melted during the thermal spraying, and the unmelted portion is also softened to have a shape that is slightly crushed due to collision during the thermal spraying. Therefore, the particle size of the atomized powder used and the particle size of the unmelted particles do not correspond one to one. However, as shown in the micrograph of FIG. 1, the unmelted particles are circular and are easily distinguishable from the surrounding molten matrix.

FIG. 3 is a vertical cross-sectional view of a cylinder liner whose inner peripheral surface is coated with a sprayed layer of the present invention, and FIG. 4 is a vertical cross-sectional view showing a part of a piston portion of an engine. Cylinder liner 1
Is fixed to the bore of the cylinder block 2 and the piston 3 is inserted into the cylinder liner 1. A piston ring 5 is mounted in a piston ring groove 4 formed in the piston 3, and the outer peripheral surface of the piston ring 5 is in contact with the inner peripheral surface of the cylinder liner 1.

The material of the piston ring 5 is steel, cast iron, titanium, titanium alloy or the like, and for example, martensitic stainless steel is used. The outer peripheral surface of the piston ring 5 is coated with, for example, hard Cr plating 6.

The base material of the cylinder liner 1 is steel, cast iron, aluminum alloy or the like, and is made of, for example, carbon steel, and the inner peripheral surface is described in any of Examples 1 to 18 shown in the seizure test and wear test. The sprayed layer 7 made of steel is formed. The thickness of the sprayed layer 7 is 30 to 300 μm, and more preferably 50 μm or more and 100 μm or less.

As described above, if the base material of the cylinder liner 1 is made of carbon steel, it is easy to process and can be manufactured at low cost, and a cylinder liner with high strength, thin wall, light weight, and excellent sliding characteristics is provided. it can. If the base material of the cylinder liner 1 is an aluminum alloy, it is possible to provide a cylinder liner having high strength, light weight, and excellent sliding characteristics.

The sprayed layer is HVOF (High Ve).
It is not limited to the formation by a locality oxy-fuel spraying) spraying method, and may be formed by a plasma spraying method, an arc spraying method or the like.

Further, the wear resistant sprayed layer of the present invention is not limited to covering at least the sliding surface of the cylinder liner, but at least the sliding surface of another sliding member (for example, the cylinder block to which the cylinder liner is not mounted ( Material: cast iron or aluminum alloy, etc.) can also be applied to at least the bore inner peripheral surface).

[0059]

As described above, according to the present invention, it is possible to provide a sprayed layer having excellent seizure resistance and abrasion resistance.

When the thermal sprayed layer of the present invention is applied to a steel cylinder liner, the cylinder liner can be inexpensive, high-strength, thin-walled, light-weight and compact.

[Brief description of drawings]

FIG. 1 is a 100 × micrograph showing the structure of a sprayed layer of the present invention.

FIG. 2 is a graph showing the results of a wear test.

FIG. 3 is a vertical cross-sectional view of a cylinder liner whose inner peripheral surface is coated with a sprayed layer of the present invention.

FIG. 4 is a vertical sectional view showing a part of a piston portion of the engine.

FIG. 5 is a diagram schematically showing a reciprocating wear tester.

[Explanation of symbols]

 1 Cylinder Liner 2 Cylinder Block 3 Piston 4 Piston Ring Groove 5 Piston Ring 6 Hard Cr Plating 7 Thermal Spray Layer 10, 12 Test Specimen 11 Test Stand 13 Hydraulic Unit 14 Crank Mechanism 15 Hydraulic Load Indicator 16 Load Cell 17 Recorder

Claims (13)

[Claims] 1. C0.25 to 2.2% by weight, Cr,
It consists of steel containing 13.0% or less of one or more of Mo, W, and V, and unmelted particles are dispersed in the matrix at an area ratio of 10 to 50%, and the unmelted particles and the matrix. Hardness is different, the higher hardness is H
A wear-resistant sprayed layer having a V400 or more. 2. The wear resistant sprayed layer according to claim 1, wherein the unmelted particles have a hardness higher than that of the matrix. 3. The wear resistant sprayed layer according to claim 1, wherein the matrix has a hardness higher than that of the unmelted particles. 4. The wear resistant sprayed layer according to claim 1, wherein the hardness difference between the unmelted particles and the matrix is HV30 or more. 5. The wear resistant sprayed layer according to claim 1, wherein the particle size of the unmelted particles is in the range of 10 to 100 μm. 6. A non-melted particle is dispersed in a matrix by spraying a mixed powder composed of a steel powder having a small particle diameter intended to be melted and a steel powder having a large particle diameter intended to be dispersed while being unmelted. A method for forming a wear-resistant sprayed layer, which comprises forming a sprayed layer that has been formed. 7. The method for forming a wear-resistant sprayed layer according to claim 6, wherein the mixed powders are made of powder materials having the same composition. 8. The mixed powder is composed of two or more kinds of powder materials having different hardness after thermal spraying, and the powder having a larger particle size intended to be dispersed as unmelted particles is 7. The method for forming a wear-resistant sprayed layer according to claim 6, wherein the powder having a higher hardness and the powder having a smaller particle size intended to be melted are powders having a lower hardness after thermal spraying. 9. The mixed powder is composed of two or more kinds of powder materials having different hardness after thermal spraying, and the powder having a larger particle size intended to be dispersed as unmelted particles is 7. The method for forming a wear-resistant sprayed layer according to claim 6, wherein the powder having a lower hardness and the powder having a smaller particle diameter intended to be melted are powders having a higher hardness after thermal spraying. 10. A sliding member, wherein at least the sliding surface is coated with the abrasion-resistant sprayed layer according to any one of claims 1 to 5. 11. The sliding member according to claim 10, wherein the sliding member is a cylinder liner or a cylinder block. 12. The sliding member according to claim 11, wherein the base material of the cylinder liner is steel, cast iron or an aluminum alloy. 13. The base material of the cylinder block is cast iron or aluminum alloy.
The sliding member according to 1.