JPS61231154A - Wear resisting surface layer - Google Patents

Abstract

PURPOSE:To obtain a surface layer capable of showing excellent resistance to wear and seizure even under sliding conditions CONSTITUTION:The wear resisting surface layer consists of 10-50wt% nickel- base self-fluxing alloy as binder and the balance.

Description

[Detailed description of the invention] B. Industrial application field The present invention relates to wear-resistant surface layers.

In recent years, internal combustion engines have been designed to have higher compression ratios and faster rotation speeds in order to improve their performance, and as a result, sliding parts such as piston rings have become more resistant to wear and tear than ever before. Seizure resistance (scuff resistance) is increasingly required.

The ROM plating layer has high hardness (low wear on itself and low wear on the material it slides on), and exhibits extremely excellent wear resistance, but it has poor oil retention and is difficult to handle under high temperature and high load conditions. However, this has the disadvantage that seizure is likely to occur during sliding.

As a surface layer with improved seizure resistance, a molybdenum sprayed surface layer is used in some cases. The molybdenum sprayed surface layer has good oil retention properties because it contains pores, and has excellent seizure resistance because of its high melting point, but its wear resistance is comparable to that of a hard chrome plating layer. In addition, it has the disadvantage of being easily oxidized at high temperatures and having a short lifespan.

As a thermal sprayed surface layer that eliminates the above-mentioned drawbacks of the molybdenum thermal sprayed surface layer, a thermal sprayed surface layer formed by plasma spraying a mixed powder of ferrochrome powder, molybdenum powder, and nickel-chromium alloy powder has been adopted in some cases. However, since this sprayed surface layer also contains molybdenum, it is easily oxidized at high temperatures (
, which is a problem in terms of service life.

In addition, titania (TiOz), alumina titania (A
7! zo3-13 wt% Tio2 or AfzO3-40
wt% TiO2), chromium oxide (Cr203), zirconia-ittria (Zr02) 8-12 wt% Y2
A thermal sprayed surface layer formed by plasma spraying an oxide ceramic such as O3) has also been attempted, but it has the drawbacks of poor thermal shock resistance and brittleness.

In order to solve the problem of thermal shock resistance and brittleness of the thermal sprayed ceramic surface layer, a mixed powder consisting of titania powder, alumina powder, or a mixture of both, and nickel-chromium alloy powder or nickel-aluminum alloy powder is sprayed. A thermally sprayed surface layer is considered, but it is difficult to obtain a uniform thermally sprayed surface layer due to the difference in viscosity and specific gravity between the ceramic particles and the alloy particles.

As described above, a surface layer that exhibits fully satisfactory sliding characteristics under high temperature and high load sliding conditions has not yet been obtained.

C. Purpose of the Invention The present invention has been made in view of the above circumstances, and includes:
The objective is to provide a surface layer that exhibits excellent wear resistance and seizure resistance even under high temperature and high load sliding conditions.

2. Structure of the invention, that is, the present invention relates to a wear-resistant surface layer consisting essentially of 10 to 50% by weight of a nickel-based self-fluxing alloy as a binder, and the remainder consisting of chromium oxide powder with a particle size of 1 to 74 μm. .

Self-fluxing alloys are broadly classified into nickel-based self-fluxing alloys and cobalt-based self-fluxing alloys. Nickel-based self-fluxing alloy has Hv550~
Since it has a high hardness of 800, which is close to the hardness of chromium oxide (CrzO3) HV2O3-1200, it is suitable for forming a wear-resistant surface layer as a binder for chromium oxide powder.

The nickel-based self-fluxing alloy used in the present invention is JIS H
MSFNi specified in 8303r Self-Fusing Alloy Thermal Spraying
l, MSFNi2, MSFNi3, MSFNi4, MS
Any of FNi5 can be used, but boron2~
4% by weight (hereinafter, weight% is simply expressed as "%") and 2 to 5% silicon is suitable. If both boron and silicon are less than 2%, the hardness of the surface layer formed will be low and the effect of improving wear resistance will not be significant, and if boron exceeds 4%,
If the silicon content exceeds 5%, the surface layer formed becomes too hard and brittle, resulting in poor wear resistance and abrasion of the mating sliding material. Therefore, the boron content is preferably in the range of 2 to 4%, and the silicon content is in the range of 2 to 5%.

The nickel-based self-fluxing alloy used in the present invention includes, for example, 10 to 20% chromium, 2 to 4% boron, 2 to 5% silicon,
A commercially available material consisting of 0.1 to 1% carbon and the remainder substantially nickel may be used.

The surface layer of the sliding member according to the present invention is made by coating the surface of chromium carbide powder particles having a particle size of 1 to 74 μm with fine nickel-based self-fluxing alloy powder having the above chemical composition using a resin or the like as a binder. Formed by plasma spraying. Alternatively, the chromium oxide powder and the self-fluxing alloy powder may be mixed and granulated, and then the granulated powder may be plasma sprayed. If the particle size of these granulated powders is less than 5 μm, it is difficult to introduce it into the plasma jet stream, and if it exceeds 105 μm, it may not be completely melted during thermal spraying. desirable. The above-mentioned nickel-based self-fluxing alloy exhibits a network shape in the sprayed surface layer and increases the bonding strength. Using a simple flour mix,
Due to the difference in particle size and specific gravity between the two, it is difficult to obtain a uniform sprayed surface layer, that is, the self-fluxing alloy does not form a network over the entire surface.1. It becomes difficult to obtain the bonding strength of the self-fluxing alloy.

If the amount of the above-mentioned nickel-based self-fluxing alloy is less than 10%, the effect contributing to bonding strength will not be significant, and if it exceeds 50%, the amount of chromium oxide powder will decrease and the effect of improving wear resistance and seizure resistance will be reduced. Since it is insufficient, it is set in the range of 10 to 50%.

E, Example The present invention will be specifically explained below with reference to Examples.

A large number of prismatic cast iron samples measuring 5 mm x 5 + n x 10 n + were prepared, and the materials shown in Table 1 below were plasma sprayed onto the square end faces of the samples to form a sprayed surface layer with a thickness of 0.3 mm. However, ■ is by oxygen-acetylene bombardment, and J is by plating.

Table 1 In the same table, C, D and E are wear-resistant surface layer test pieces based on the present invention. A is only chromium oxide, B is outside the scope of the present invention and has a small amount of self-fluxing alloy, F is outside the scope of the present invention and has a large amount of self-fluxing alloy. G
, H and I are comparison specimens.

In addition, chromium oxide has a particle size of 10 to 53 μm, and self-fluxing alloy has a particle size of 10 to 53 μm.
The surface of this chromium oxide powder particle is coated with a chemical composition of 11.5% Cr, 3.0% B, 3.4% St, 0
．． The balance of 4% C1 is essentially Ni.

The surfaces of the surface layers of these test pieces were polished to a surface roughness of 0.8 to 1.5 μm, and subjected to wear tests and seizure tests. Ceramics have recently been attracting attention as sliding mating materials due to their excellent wear resistance, and in view of the fact that attempts are being made to develop so-called ceramic engines, pressureless sintered silicon carbide (α-3i C) or silicon nitride (Si3N
I chose 4).

The sliding surfaces of these sliding mating materials were polished to a surface roughness of 0.8 to 1.5 μm.

A sketch (400x magnification) of the microscopic structure of a wear-resistant surface layer test piece according to the present invention is shown in FIG. 1, taking test piece E as an example. The test piece 5 consists of a cast iron base material 5c, a nickel-aluminum base sprayed layer 5b provided to improve the adhesion of the sprayed surface layer, and a sprayed surface layer 5a. The sprayed surface layer 5a is composed of chromium oxide particles 5d and a self-fluxing alloy 5e surrounding them in a network shape, and has pores 5.
This is a photograph of a secondary electron image (magnification: 2000 times) of the thermal spray raw material powder used to create r and D, taken with a scanning electron microscope.

(i) The seizure test test device is schematically shown in FIG. 3 and FIG. 3, which is a side view taken along line IV-IV in FIG. 3, and is detachable from the stator holder 1. installed diameter 8
Lubricating oil is applied to the center of the polished disk 2 with a thickness of 0 mm and a thickness of 10+ m through an oil filling hole 3 from the back side.

A pressing force P is applied to the stator holder 1 by a hydraulic device (not shown) at a predetermined pressure toward the right in the figure.

A rotor 4 is provided opposite to the disk 2, and is rotated at a predetermined speed by a drive device (not shown). Test piece holder 4 attached to the end face of the rotor 4 relative to the disk 2
On a, four test pieces 5 are removably attached at equal intervals on a concentric circle with the square end face (in this example, the surface 5a in FIG. 1) as a sliding surface, and are slidable on the disk 2. It is.

In such a device, a predetermined pressing force P is applied to the stator 1.
The test piece 5 is brought into contact with the disc (mate material) 2 under a predetermined surface pressure, and the rotor 4 is rotated while lubricating the sliding surface from the lubricating hole 3 at a predetermined lubricating speed. The pressure acting on the stator 1 is increased stepwise at regular intervals, and the torque (torque generated by frictional force) generated on the stator 1 due to the friction between the test piece 5 and the mating disk 2 due to the rotation of the rotor 4 is T. is applied to the load cell 7 via the spindle 6, and the change is read by the dynamic strain meter 8 and recorded on the recorder 9. It is assumed that seizure has occurred when the torque T increases rapidly, and the quality of the seizure resistance is determined based on the magnitude of the increase.

The test conditions are as follows.

Friction speed = 8 m 156 (Lubricating oil: Motor oil 5AE30 at 2 ml/min Lubricating contact pressure 20 kg/c++t at the start of the crab test, increasing by 10 kg/crl every 3 minutes thereafter) Mating disc material: Normal pressure sintering The α-3iC or Si3N4 test results are shown in Table 2 below.

Table 2 From the same table, based on the present invention (wear-resistant surface layer test pieces C, D
It can be seen that the seizure resistance of specimens F and E is clearly improved compared to comparative specimen F-J. Comparative test pieces A and B showed approximately the same surface pressure at which seizure occurred as the wear-resistant surface layer test pieces C, D, and E based on the present invention, but both A and B showed that after the test,
While tortoiseshell-shaped cracks were observed on the sliding surface, C, D,
No such cracks were observed in E.

(11) The outline of the wear test test apparatus is shown in FIG. , the outer peripheral surface has a surface roughness of 0.8~
(Polished to 1.5 μm) 12 is rotatably installed at a predetermined speed by a drive device (not shown) installed outside the furnace. In the figure, 13a is a furnace core tube, 13b is a resistance heating element, and 13c is a heat insulating material. The test piece 5 is attached to the lever 11 so that the sprayed surface layer 5a is in sliding contact with the outer peripheral surface of the cylindrical body 12.
installed on. The lever 11 has electric furnaces 13 at both ends.
It protrudes outward, with one end serving as a fulcrum and a weight (not shown) attached to the other end, so that the test piece 5 contacts the cylindrical body 12 with a predetermined surface pressure.

Using such a device, the temperature inside the electric furnace 13 can be increased to 35%.
Maintained at 0℃, contact load 5kg (surface pressure 20kg/cfl
I), friction speed 0.5m/5eC1 friction distance 1.3km
, the test was conducted under non-lubricated conditions.

The test results are shown in FIG. The amount of wear is shown by the wear volume for the test piece 5, and by the radial cross-sectional area of a tubular mark produced on the outer circumferential surface due to wear for the mating cylindrical body 12.

From FIG. 6, wear-resistant surface layer test piece C based on the present invention,
It can be seen that D and E have less wear than comparative test pieces F, GSH, I, and J. Furthermore, the sliding surface was smooth after the test. The abnormal wear of comparative test pieces ① and J indicates that the thermal sprayed surface layer or the plating layer has disappeared and the wear has extended to the cast iron base material. Comparative test pieces A and B are
Although the amount of wear appears to be small, peeling of the sprayed surface layer was observed on a part of the sliding surface, and there was a lot of wear on the mating material.

Test piece CSD has less wear both on itself and on the other material.
and E.

As described in the detailed description of the invention, the wear-resistant surface layer according to the invention comprises:
The structure is made up of 10 to 50% nickel-based self-fluxing alloy as a binder, and the remainder is essentially chromium oxide powder with a particle size of 1 to 74 μm, so that hard nickel with a network of hard chromium oxide particles is formed. The structure is strongly bonded by the base self-fluxing alloy. As a result, seizure resistance is significantly improved, and in addition, it exhibits excellent wear resistance even under severe sliding conditions such as high temperatures and no lubrication, and durability is significantly improved.

Therefore, when using the sliding member having the wear-resistant surface layer according to the present invention, the period between engine overhauls and subsequent overhaul salts is greatly extended, and the industrial utility value of the present invention is great.

[Brief explanation of drawings]

The drawings all show examples of the present invention. Figure 1 is a sketch of the microscopic structure of the wear-resistant surface layer, and Figure 2 is an electron micrograph (secondary electron image) of thermal spray raw material powder particles. Figure 3 is a partial sectional view showing the main parts of the test equipment used in the seizure test, Figure 4 is a side view taken along the line IV-IV in Figure 3, and Figure 5 is the main part of the test equipment used in the wear test. The cross-sectional view and FIG. 6 are graphs showing the results of the wear test. In addition, in the symbols shown in the drawings, 1...Stator 2...Mating disk 3...Oil filling hole 4. ......Rotor 5...Test piece 5a...Thermal sprayed surface layer 5b...Thermal sprayed base layer 5c... ......Cast iron base material 5d...Chromium oxide particles 5e...
...Nickel-based self-fluxing alloy 5f...Pore 7...Load cell 8...Dynamic strain meter 9... . . . Recorder 11 . . . Lever 12 . . . Matching cylindrical body 13 . . . A tubular electric furnace.

Claims (1)

[Claims] 1. A wear-resistant surface layer consisting essentially of 10 to 50% by weight of a nickel-based self-fluxing alloy as a binder, and the remainder consisting of chromium oxide powder with a particle size of 1 to 74 μm.