JPS62177159A - Sintered alloy member having excellent wear resistance - Google Patents

Abstract

PURPOSE:To obtain a sintered alloy member having excellent wear resistance, hardness and toughness by uniformly dispersing fine carbide such as Cr3C2 having high hardness into a sintered alloy matrix made of a specific compsn. consisting of C, Cr, P, Mo, B and Fe. CONSTITUTION:The carbide such as Cr3C2, NbC, TaC, TiC, WC, VC, ZrC or HfC which has <=10mu average grain size, has about >=1,300 Hv hardness and does not decompose at a sintering temp. of about 1,000-1,130 deg.C is dispersed into the sintered alloy matrix which contains 1.0-4.0wt% C, 4.0-7.0% Cr and least one kind of 0.5-2.0% P, 2.0-6.0% Mo and 0.5-3.0% B and consists of the balance Fe and unavoidable components. The sintered alloy member having the sorbite structure which is excellent in the wear resistance, hardness and toughness is thus obtd. The above-mentioned member can be made into a sliding member having an excellent sliding characteristic by forming fine oil holding recesses on the surface with good dispersibility by buffing, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a sintered alloy full material that is used as a sliding member subject to high blood pressure, has excellent wear resistance, and does not cause H1 damage to a mating member.

(Prior Art) In recent years, with the increase in speed and output of vehicles, the wear resistance and resistance of internal combustion engine valve train members, especially rocker arm butt surfaces, cams, sleeves, and valve seats, which are subject to high surface pressure, has increased. Requirements regarding scuffing resistance and pitting resistance are becoming extremely strict, and in this case, it is also necessary to avoid damaging the mating assembly.

Conventionally, high hardness carbides such as NbC are precipitated and dispersed in a sintered alloy matrix using liquid phase sintering to produce sintered alloy members that are applied to sliding members that are subject to high surface pressure. (Special Publication No. 60-3318)
(See Publication No. 1). However, in this sintered alloy member,
There was a problem in that carbides tend to become coarse, which hinders improvement in wear resistance.

Therefore, in JP-A-59, a method was developed in which pre-prepared carbide particles such as NbC were mixed with alloy powder and then sintered.
This is proposed in Japanese Patent No.-118859.

However, in conventional sintered alloy fall grinding, there is still room for improvement in the grain size of carbides related to wear resistance, and since Ni is contained in the sintered alloy matrix, residual austenite is present. , W had the problem of being soft and having low strength.

Another problem is that the recesses that are formed when the surface of the sintered metal member is roughened by puff polishing or chemical etching are not miniaturized, making them unsuitable for use as oil retaining parts.

(Object of the Invention) The present invention has been made in view of the above-mentioned conventional problems, and has excellent wear resistance by uniformly dispersing fine, high-hardness carbides, and has a sorbite structure that improves hardness and The object is to provide a sintered alloy member that is also excellent in toughness.

Another object of the present invention is to provide a sintered alloy member in which fine oil retaining recesses are formed with good dispersion by puff polishing or chemical etching.

(Structure of the Invention) ``In order to achieve the above object, the sintered alloy member of the present invention having excellent wear resistance has a weight ratio of 1.0 to 4.0% C.
r: 4.0-7.0%, and P: 0.5-2.0
%.

MO: 2.0-6.0%, B: 0.5-3.
Cr3C2, NbC, TaC, T having an average particle size of 10μ or less in a sintered alloy matrix containing at least one of 0% and the remainder consisting of Fe and unavoidable components.
It is characterized by having a sorbite structure in which at least one type of carbide among iC, WC, VC, ZrC, and HfC is dispersed.

The reason why the composition is limited as described above in the present invention will be described below.

(a) The C component is solid-dissolved in the sintered alloy matrix to strengthen it, and forms a low melting point ternary collection with Fe and at least one of P, Mo, and B to form a liquid phase. generate,
It has the effect of making the sintered alloy member denser. If the content is less than 1.0%, the amount of liquid phase is insufficient, so the sintered density is 7.0 g/cff! As can be seen from the fact that it is less than 100%, the number of pores increases and the abrasion resistance decreases. Also,
When the content exceeds 4.0%, the amount of liquid phase becomes excessive,
In addition to causing deformation during sintering, the amount of carbides increases and becomes brittle.

Therefore, the C content is preferably 1.0 to 4.0%.

(b) Cr The Cr component solidly dissolves in the sintered alloy matrix to increase strength, and also combines with C to form Cr carbide to improve wear resistance. The content in the sintered alloy matrix is 4.
If it is less than 0%, the desired wear resistance cannot be obtained;
．． If it exceeds 0%, the carbides tend to become coarse and the toughness decreases, so it should not be exceeded. therefore,
The content of Cr is preferably 4.0 to 7.0%.

(c) P, Mo, B P, Mo, and B all form a ternary assembly together with Fe and c, are brought into a liquid phase during sintering, and contribute to the densification of the sintered body. However, the content is less than 0.5% in the case of P, M
If it is less than 2.0% in the case of o, and less than 0.5% in the case of B, the amount of liquid phase will be insufficient, leading to a rapid increase in the amount of wear. In addition, when the content exceeds 2.0% for P, 6.0% for Mo, and 3.0% for B, the amount of liquid phase becomes excessive and the sintered alloy member This leads to changes and embrittlement during sintering. Therefore, the P content is between 0.5 and 2.
0%, M.

The content of B is 2.0 to 6.0%, and the content of B is 0.5 to 3.
．． Preferably it is 0%.

(d) CrlCIl NbC, TaC, Tic, wc.

Since carbides such as VC, ZrC, and Hf all have high hardness of Hv1300 or more, it is possible to improve wear resistance by dispersing them in the sintered alloy matrix.

The reason why the average particle size of the carbide is preferably 10 μm or less is based on the following reason. That is, the average particle size is 10
If μ is exceeded, the carbide tends to become coarse in the sintered alloy matrix and the dispersibility becomes poor, so there is a risk of damaging the mating member, and if the carbide becomes coarse, the sintered alloy matrix that holds the carbide This is because when a sliding member to which the sintered alloy member is applied is used, the carbide tends to fall off and the sliding properties deteriorate. moreover,
This is because if the dispersibility of the carbide is poor, even if the surface of the sintered alloy member is subjected to puff polishing or the like, it will be difficult to form oil retaining portions with good dispersibility that are convenient for forming an oil film.

Furthermore, among the carbides having high hardness, the above-mentioned Cr, C
, etc. are preferable for the following reasons.

That is, the carbides such as Cr and C2 have a content of 1000 to 1
This is because it does not thermally decompose at the sintering temperature of 130° C. and remains in the sintered alloy matrix with the same particle size as when it was added.

On the other hand, carbides such as MoC, which are thermally decomposed at the above sintering temperature, become coarse when recrystallized after decomposition, causing the same problems as when the average particle size exceeds 10 μm. This is not preferable in terms of invention.

(Example) Hereinafter, a specific example in which the sintered alloy member according to the present invention is applied to a sliding member will be described.

In order to make the sintered alloy member of the present invention suitable as a sliding member, it is necessary to use a Fe-P (or Mo, B)-C eutectic alloy powder, a 5OS410 alloy powder, a hardness of Hv 1300 or more, and a particle size of 10μ. Below, the sintering temperature is 1000 to 113
Carbide powder (Cr3C2, N
bC, TaC, TiC.

Puff polishing or chemical etching is applied to the sliding surface of a sintered alloy member made of WC, VC, Zr, C, HfC,
By preferentially polishing or etching the matrix in the surface structure, the sliding surface is made uneven, with a surface roughness of Rmax 1.0 to 3.0μ, and the recesses on the sliding surface make it easy to retain oil. A sintered metal member that can be formed into a recess is manufactured.

The hardness of the carbide is set to Hv1300 or more because Hv
If it is less than 1300, the desired excellent wear resistance cannot be obtained,
Further, since carbide is easily polished by puff polishing, it becomes difficult to make the sliding surface uneven. The surface roughness of the sliding surface made uneven by puff polishing or chemical etching is Rma
If it is less than xl or Oμ, a sufficient oil reservoir effect cannot be expected, and R
If Rmax exceeds 3.0μ, there is a risk of damaging the mating member, so the surface roughness is preferably in the range of Rmax 1.0 to 3.0μ.

Next, a more specific example will be described.

<Example 1> C: 1.94% by weight, P: 1.12% by weight, M
o: 90% by weight of wear-resistant eutectic alloy powder with a particle size of 150 mesh or less consisting of 4.78% by weight, near Cr, 95% by weight and the balance Fe, and NbC powder 10 with a powder particle size of 1.1μ
After kneading 97% by volume of mixed powder obtained by mixing % by weight with 3% by volume of acrylic resin dissolved in toluene,
．． 5mm sheet, width 16.5mm, length 18.5mm
After cutting the pieces into 1/4 inch pieces and adhering them to a chip material (steel material) using an acrylic resin-based grafting agent, the pieces were heated to 300°C at a heating rate of 10°C/min in a hydrogen atmosphere and held at that temperature for 60 minutes. Preliminary sintering was performed. Next, this was heated to 1100°C in a vacuum furnace at a heating rate of 10°C/min, and the temperature was increased to 2
After holding for 0 minutes, the temperature was lowered to 900℃, and the temperature was kept at this temperature for 3
After holding for 0 minutes, harden with N2 gas. Next, by holding it in a vacuum furnace at 560° C. for 100 minutes and tempering it, a tt% alloy flake having a Rockwell C hardness of 59 was obtained.

An AQ rocker arm was obtained by casting this sintered metal member using AQ die casting. Next, this Af1 rocker arm is machined, and after grinding the sliding surface, it is puff-polished with an abrasive blue rod to make the surface uneven, and the AQ rocker arm has a surface roughness Rmax of 1.2 to 2.1μ. was gotten.

FIG. 1 shows a rocker arm 1 according to an example of the present invention manufactured in this manner, in which a sintered alloy member 3 according to the present invention is bonded as a sliding member to the bottom of a chip material 2 made of steel. There is. Puff polishing is applied to the surface of the sintered metal member 3 to form a sliding surface 4 that slides on the cam member.

Next, this AQ rocker arm 1 was assembled into an engine, and its sliding characteristics were evaluated by the motoring method.

The test conditions are as follows.

Engine rotation speed x test time: 2000 rpm x 100 Hr Lubricating oil: Product name [Department Apollo Bueasel 5AZ30#]; Wei lubricating oil temperature: 50°C Spring set load: 34 kg Mating member: Chill alloy cast iron camshaft treated with Tuftride Furthermore, the present invention example Instead of the sintered alloy member 3, the composition is C: 2.4%, Cr: 11.3%, M in weight ratio.

A conventional rocker arm using a sintered alloy member having: 1.8% and the balance Fe was tested under the same conditions as above. Test results for these examples of the present invention and conventional examples are shown in Table 1 below. All numbers are the amount of wear,
The values outside the parentheses are the average value, and the values inside the parentheses are the minimum and maximum values.

Table 1 As is clear from the above test results, in the example of the present invention, the amount of wear on the sliding member was reduced to -, and the amount of wear on the opposing member was reduced by about half, achieving a significant improvement in the sliding characteristics. be done.

Next, the structure of the sintered alloy member will be explained using the photographs (magnification: 400) shown in FIGS. 2 to 4.

FIG. 2 is a photograph of the conventional example used in the test.

The matrix is a bainite structure, and the rod-like or granular white parts are made of Or carbide or Cr-Mo composite carbide.

FIG. 3 shows, as a comparative example, the structure of a sintered alloy member manufactured under the same conditions as those of the present invention but without dispersing NbC. The matrix is a sorbite structure, and the white part is made of Cr carbide or Cr-Mo composite carbide.

FIG. 4 is a photograph of an example of the present invention (Example 1) used in the test. The matrix is a sorbite tissue.

Unlike the conventional example and the comparative example, a cottony white part is formed at the boundary between the matrix and the white part. The flocculent white part consists of NbC. Furthermore, it has been confirmed that the white portion is composed of a Cr carbide and a composite carbide of NbC or Cr-Mo.

In this way, fine NbC is uniformly dispersed, so
Excellent wear resistance is provided to the sintered alloy member. Also,
Since the structure is a sorbite structure, high hardness and excellent toughness are provided.

Next, referring to the photographs shown in FIGS. 5 and 6, the sliding surfaces of the sintered alloy members of the conventional example and the example of the present invention after being puff-polished will be described. All photographs were taken using a scanning electron microscope.
This photo was taken at a magnification of 1000.

FIG. 5 is a photograph of a conventional example. The dark colored parts are convex parts, htJ, and dark colored parts are concave parts. As shown in the photo, since the four parts formed are extremely large, the recesses have poor oil storage function.

On the other hand, in the example of the present invention shown in the photograph of FIG. 6, fine recesses are present in a dispersed state as shown in the photograph, so that the recesses effectively act as oil retaining recesses. The reason why the rocker arm of the present invention had better sliding characteristics than the conventional example in the above test is due to the difference in the structure of the recess.

<Example 2> 83% by weight of alloy powder with the same composition and friction resistance as Example 1
After adding 2% by weight of acetone diluted with acetone to a mixed powder of 17% by weight of TaC powder with a particle size of 1.5μ and kneading, chips of the green compact were formed with a press pressure of 6.0 ton/-. Molded. Next, this compacted powder chip was pre-sintered in a hydrogen atmosphere at 600°C, and then placed in a 1120'c vacuum furnace for 20 minutes.
It was held for a minute to sinter. Furthermore, the temperature dropped to 950℃,
After holding for 30 minutes, it was quenched with N gas.Then, this was held at 550° C. for 100 minutes to temper, and a sintered alloy member with a Rockwell C hardness of 58 was obtained.

This sintered alloy member was made into a rocker arm using the same method as in Example 1, and machined to a surface roughness Rmax of 1.6 to
A 2.5μ AQ rocker arm was obtained.

FIG. 7 is a photograph (400x magnification) showing the structure of the sintered alloy member. As in Example 1, the matrix is a sorbite structure. The white part is made of Cr carbide or Cr-Mo composite carbide. The flocculent white 81) located at the boundary between the matrix and the white part consists of TaC. As the photo shows,
TaC is fine and has good dispersibility.

(Effects of the Invention) As described above, the sintered alloy member of the present invention provides the following effects.

(1) Excellent wear resistance because fine, highly hard carbides are uniformly dispersed.

(2) Since the structure is a sorbite structure, it has excellent hardness and toughness.

(3) Puff polishing or chemical etching creates fine oil-holding recesses with good dispersion.

A sliding member provided with the recessed portion has excellent sliding properties.

[Brief explanation of drawings]

Fig. 1 is a partial sectional view of the rocker arm, Fig. 2 is a photograph showing the structure of a conventional sintered alloy member (400 magnification), and Fig. 3 is a photo showing the structure of a comparative sintered alloy member (400 magnification).
), FIG. 4 is a photograph ((8 ratio: 400)) showing the structure of the sintered alloy member of Example 1, and FIG. 5 is a scanning type photograph showing the sliding surface of the sintered alloy part H of the conventional example after puff polishing. Photo taken with an electron microscope (
Fig. 6 is a photograph taken by a scanning electron microscope showing the sliding surface of the sintered alloy member of Example 1 after puff polishing (magnification: 1000).
FIG. 7 is a photograph (magnification: 400) showing the structure of the sintered alloy member of Example 2. 3...Sintered alloy member. Genus 1 Figure 5 stations: 6th decoy 2nd year 3rd year

Claims (1)

[Claims] (1) C: 1.0-4.0%, Cr: 4.0-4.0% by weight
7.0%, P: 0.5-2.0%, Mo: 2.0
~6.0%, B: at least one of 0.5 to 3.0%, and the balance is Fe and unavoidable components.
r_3C_2, NbC, TaC, TiC, WC, VC,
A sintered alloy member having excellent wear resistance, characterized by having a sorbite structure in which at least one type of carbide among ZrC and HfC is dispersed.