JPH05140678A - Copper base alloy for building up welding excellent in wear resistance - Google Patents

Abstract

PURPOSE:To improve the wear resistance of a copper base alloy for building up welding at a high temp. as for a dispersion strengthening type wear resistant copper base alloy. CONSTITUTION:This copper base alloy has a compsn. constituted of, by weight, 5 to 30.0% Ni, 0.5 to 5.0% Si, 0.5 to 3.0% B, 2 to 30% Co and the balance Cu with inevitable impurities (where the total of alloy components other than Cu does not exceed 60%). A part of Co can be substituted by Fe. Moreover, at least one kind among high m.p. carbides, Pb, Sn and Zn may be added. The hard grains of Co borides are small in the deterioration in hardness at a high temp. and contribute to the improvement of its wear resistance at a high temp. and on heavy loads.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper (Cu) base alloy, and more particularly to a dispersion strengthened copper base alloy for overlay welding, which has excellent wear resistance.

[0002]

2. Description of the Related Art Cu is a wear-resistant material for copper-based alloys.
Beryllium copper with beryllium (Be) added to it or a precipitation hardening alloy such as a Cu-Ni-Si alloy known as Corson alloy, or Si in a copper-based matrix.
O ₂ , Cr ₂ O ₃ , BeO, TiO ₂ , ZrO ₂ , Mg
A dispersion-strengthened alloy in which particles mainly composed of a hard oxide such as O or MnO are dispersed is known.

In particular, beryllium copper is as strong as steel (1
It has a tensile strength of 00 kg / mm ² or more) and a high hardness (hardness of Hv 300 or more) among copper-based alloys. However, in the case where such precipitation hardening treatment (age hardening treatment) is applied, when the temperature (350 to 450 ° C.) higher than the precipitation (aging) temperature is reached, the hardness sharply decreases,
It is insufficient as a wear resistant member. In addition, such a precipitation hardening treatment is difficult to apply to a large-sized member, and distortion due to heat treatment becomes a problem, which requires a long time for the treatment. Further, since the precipitation is caused by diffusion in the solid, the size of the precipitated particles is as small as several μm. Therefore, even if hardness is obtained, it is often large under wear conditions involving sliding. May cause wear.

Further, among the dispersion-strengthened copper-based alloys, those obtained by the internal oxidation method form oxide particles by diffusion of oxygen in the solid, so that the dispersed particles are different from those of the precipitation type. Similarly, it becomes minute. Moreover,
Since it needs to be treated at a high temperature for a long time for diffusion in a solid, it is difficult to apply it to a large-sized member, and there is a problem of strain generation. Further, in the product obtained by the sintering method, the size of dispersed particles can be easily controlled by changing the particle size of the raw material powder, but it is difficult to control the uniform dispersion on the order of microns. .. Moreover, if a copper-based alloy layer is to be locally formed as in the case of overlaying, the entire substrate to be processed must be heated to the sintering temperature, which causes deformation and distortion of the processed member. Therefore, it is not suitable for build-up.

Therefore, the applicant of the present invention, as a wear-resistant copper-based alloy for build-up, crystallizes hard particles of silicide or boride on a Cu-Ni-Fe- (B) -Si-based copper-based alloy by crystallization. A dispersed copper-based dispersion strengthened alloy has been proposed in JP-A-63-157826. By dispersing the hard particles of Fe-Ni-based silicide and boride, it was possible to improve wear resistance as compared with the conventional material.

By the way, the temperature of an exhaust valve of an internal combustion engine (for example, an automobile engine) is 70 at the face portion.
The temperature may be 0 ° C. or higher, and the exhaust gas temperature may be 1000 ° C. or higher. For this purpose, the valve seat is 70
It will come into contact with the valve at 0 ° C or higher and be exposed to gas at 1000 ° C or higher. Therefore, the surface temperature of the valve seat becomes high, and the copper-based alloy easily adheres to the valve. Then, once the adhesion occurs, the copper (Cu) base alloys come into contact with each other at the adhesion, so that the adhesion progresses violently and large wear occurs. It has been found that the copper-based alloy according to the above-mentioned proposal utilizes the strengthening effect due to the crystallization of hard particles, but cannot suppress the adhesion of the copper-rich phase of the matrix. It was also found that the adhesion of the copper-rich phase cannot be suppressed even in the conventional copper-based dispersion strengthened alloy strengthened by the precipitation of the second phase.

Therefore, the present applicant has proposed a method in which zinc (Zn) and tin (Sn), which are more likely to be oxidized than copper, are dissolved in the primary crystal of the copper base in order to suppress the adhesion of the copper-rich phase of the matrix. (JP-A-3-60895) and a method of dispersing lead (Pb) between copper-based α-phase dendrites (dendritic crystals) (JP-A-3-87327) have been proposed. Further, instead of adding boron (B) (formation of boride), molybdenum (M
o) was added to form a molybdenum silicide to improve the lubricity and improve it (Japanese Patent Application No. 3-13).
0737).

Further, the above-mentioned proposed Cu-Ni-Fe-
In the case of (B) -Si-based copper-based alloy Fe-Ni-based silicide / boride, the hardness at high temperature may decrease. Wear resistance tends to be inferior. Therefore, chrome (C
r) is added to disperse the hard particles of Fe-Ni-Cr-based silicide and boride.
No. 31, and further, a Cu-Ni-Cr-B-Si-based copper-based alloy capable of removing iron (Fe) was proposed in Japanese Patent Laid-Open No. 1-152232.

[0009]

Although the wear resistance property against sliding wear is improved by the above-mentioned proposed copper-based alloy, in particular, the one having higher wear resistance against abrasive wear is required. ing. Therefore, an object of the present invention is to provide a copper-based alloy for build-up, which is sufficiently excellent in wear resistance.

[0010]

[Means for Solving the Problems] The above-mentioned object is Ni: 5.
~ 30.0wt%, Si: 0.5-5.0wt%, B: 0.5-3.0
wt%, Co: 2 to 30 wt% (however, the total of these alloy components does not exceed 60 wt%), and the balance is a hardfacing copper-based alloy with excellent wear resistance composed of Cu and inevitable impurities. It

It is also possible to replace part of Co with Fe (provided that Co ≧ 2 wt%). Further, the above composition may contain one or more of high melting point carbides, Pb, Sn and Zn.

The dispersion-strengthened copper-based alloy according to the present invention, like the previously proposed alloy, is deposited (build-up) on a metal substrate by using high-density heating energy such as laser, TIG arc, plasma arc, and electron beam. ) Is easily formed. In this case, the copper-based alloy is prepared in the form of powder or welding rod.

[0013]

The reasons for limiting the composition components in the present invention are as follows. Ni forms a solid solution with Cu to strengthen the Cu-based matrix, forms a hard Ni silicide (densitide) between dendrites, and enhances wear resistance by dispersion strengthening. Further, they exist as silicides and borides in the hard particles that are uniformly dispersed in the matrix after the separation of the two liquid phases, and play an important role in ensuring wear resistance. If it is less than 5%, the effect is not sufficiently exhibited, while if it exceeds 30%, the separation of two liquid phases is suppressed,
It becomes difficult to secure wear resistance. Further, the toughness of the hardfacing alloy (layer) is reduced.

Si is a silicide forming element, and mainly Ni
And Fe and Co to form a compound (silicide), which further contributes to the strengthening of the Cu-based matrix and ensures wear resistance and the like. If the amount is less than 0.5%, it is insufficient to form hard silicide particles, while if it exceeds 5%,
The toughness of the build-up layer (bead) is reduced, and cracking is observed.

B mainly forms a compound with Co, Fe and Ni to form hard particles. These hard particles contribute to ensuring wear resistance. If the amount is less than 0.5%, it is difficult to secure sufficient wear resistance, and if it exceeds 5.0%, the toughness of the overlay alloy (layer) is impaired and cracking is likely to occur.

Co hardly forms a solid solution with the Cu-based matrix, promotes the separation of two liquid phases, and forms hard particles mainly as a boride. Since this boride has a relatively small decrease in hardness at high temperatures, it improves wear resistance at high temperatures and wear resistance at high loads. If the amount is less than 2%, the effect cannot be obtained. On the other hand, if the amount exceeds 30%, the aggressiveness to the partner material is deteriorated and the toughness of the overlay alloy is deteriorated.

Fe has the same effect as Co and is added so as to replace a part of Co. Although Fe lowers the heat resistant temperature of the hard particles, the balance with the total amount of wear may be better than in the case of adding Co alone, in consideration of the opponent attacking property. To secure the characteristics under high load, Co
≧ 2% is required, and if the total amount of Co and Fe is less than 2%, the wear resistance is not sufficient, and if it exceeds 30%, the aggressiveness to the mating material deteriorates and the toughness of the overlay alloy decreases. ..

The high melting point carbide is dispersed in the matrix and has the effect of further improving the wear resistance. The high melting point carbide to be additionally added is a carbide having a melting point of 1500 ° C. or higher and substantially not reacting with the build-up alloy (solid solution, crystallization, etc.). For example, TaC, TiC, Cr ₃ C ₂ ,
VC, NbC, etc. The amount of the high melting point carbide added is preferably 1 wt% or more in order to exert the wear resistance effect, while if it exceeds 20 wt%, the weldability is deteriorated, which is not desirable.

Pb is added as an element which brings about a solid lubricating action in a high temperature atmosphere. The amount of Pb added is preferably 2 wt% or more in order to obtain the effect of improving the cohesive wear characteristics due to the solid lubrication action. On the other hand, when it exceeds 20 wt%, the dispersed hard particles agglomerate and the attacking property of the mating material increases. So undesirable.

Sn and Zn are added in order to improve the adhesion resistance of the Cu-based alloy (formation of oxide film by Cu-based primary crystal). The amount of Sn added is preferably 3 wt% or more in order to improve the effect of adhesion wear characteristics, while 15 wt%
If it exceeds%, cracking may occur when overlaying with laser or TIG, which is not desirable. Also, the amount of Zn added is preferably 3 wt% or more in order to obtain the effect of improving the cohesive wear characteristics, and on the other hand, when it exceeds 30 wt%, cracking may occur during overlaying, which is not desirable.

[0021]

The present invention will now be described in more detail with reference to the accompanying drawings by way of embodiments and comparative examples of the present invention. Samples A to I of alloy powder having the composition (wt%) shown in Table 1
(Cu-based alloys of Examples of the present invention), as a comparative example, alloy powder sample J in JP-A-63-157826 (claim 1) and JP-A-1-52232. The alloy powder sample K was welded onto an Al alloy (JIS / AC2C) substrate using a laser beam as a heat source as described later to form a build-up (welding) layer. Sample F was added with 9.0% of TaC particles as a high melting point carbide, Sample G was added with 3.0% of Pb,
Sample H was 5.0% Sn added, and Sample I was 5.0% Zn added. Sample J
And K are Cu-based alloys of comparative examples.

[0022]

[Table 1]

The overlaying (welding) here was carried out using an apparatus as shown in FIG. In FIG. 1, a metal substrate (Al
Alloy substrate: AC2C) 1 in the direction of arrow T 450 to 20
It is moved continuously at a speed of 00 mm / min. A powder 2 of samples A to K is hopper (not shown) on the metal base 1.
Is continuously supplied through the powder supply pipe 3 with a width W in a direction orthogonal to the moving direction T. On the other hand, the laser beam 4 is reflected from a laser light source (not shown) by the folding mirror 5 and the oscillating mirror 6, and is focused on the powder 2 on the metal substrate 1 to have a diameter of 0.5 to 5.0 mm. 1 x 10
Irradiation is performed with a power density of ^{2 to} 2 × 10 ⁴ w / mm ² . Here, the oscillating mirror 6 vibrates within a range of a predetermined angle by a vibrating mechanism 7 such as a galvanometer motor, so that the laser beam 4 irradiated on the powder 2 is orthogonal to the moving direction P,
That is, 10 to 10 in the direction of the width W of the powder 2 on the metal substrate 1.
Oscillate (scan) at a frequency of 500 Hz.

Here, in a state where the alloy powder or the mixed powder 2 arranged on the metal substrate 1 is rapidly melted by the irradiation of the laser beam 4, the melt 9 is the liquid phase of the alloy which becomes the Cu-based matrix, The liquid phase to be the dispersed phase is in a separated state, that is, a multi-liquid state of two liquid phases or more, and the melt 9 in the multi-liquid phase state is agitated by the laser light beam oscillating to form the two liquid phase. The above multi-liquid phase remains separated, and it looks like stirring oil in water, and finally the dispersed phase becomes a matrix, and the liquid phase that is to become particles is uniformly dispersed in the liquid phase that becomes the matrix. ..
When the melt 9 is solidified by the relative movement (scanning) of the laser beam and the metal substrate in this state, the phase to be the dispersed phase is solidified while being uniformly dispersed in the phase to be the matrix, and Co And C of the present invention in which dispersed phase particles of a silicide or boride of Ni are dispersed in a Cu-based matrix.
A welding layer 8 made of a u-based dispersion strengthened alloy is formed on the metal substrate 1.

By the irradiation of the laser beam 4 as described above, the powder 2 (particle size: 40 to 150 μm) is instantly melted to become a melt 9, and the laser beam 4 is oscillated to stir the melt 9. , Then the melt 9
When the metal substrate 1 reaches a position where the laser beam 4 is not irradiated by the movement in the T direction, the metal substrate 1 is rapidly solidified by the heat transfer to the metal substrate 1, and a buildup layer (welding layer) 8 made of a dispersion strengthened Cu-based alloy is formed. Is formed.

Laser overlaying (welding) on samples A to K
For example, laser output 4.5 kW, laser beam diameter 2.5
mm, processing scanning speed 800 mm / min, laser beam oscillating width 8 mm, power density 225 W / mm ² , oscillating frequency 200 Hz, to obtain a dispersion strengthened Cu-based alloy build-up layer 8 on the Al substrate 1. .. FIG. 2 shows a metallographic photograph (× 400) of the surface-polished structure of the overlay of Sample C. The overlay layers of Samples A, B, D and E had essentially the same structure as Sample C.

From the microstructure photograph (FIG. 2), it can be seen that relatively large hard particles are relatively uniformly dispersed in the Cu-based matrix of the copper-based alloy. These particles are
It is composed of Co and Ni silicides and borides (HV> 700).

(Abrasion test) The built-up layer (dispersion strengthened C
In order to investigate the sliding wear characteristics of the (u-based alloy), a wear test was conducted using an Ogoshi-type wear tester. In this test, as shown in FIG. 3, Stellite No. was applied to the overlay layer 8 on the metal substrate 1. 6
This is a method of examining the width L of the wear mark by rotating the rotor 10 while pressing the rotor 10 made of (Co-Cr-W-based surfacing material for surface hardening).

The test condition is a slip velocity of 0.3 m /
The sliding distance was 100 m and the final load was 20 kg. The result of such an abrasion test is shown in FIG. As is clear from FIG. 4, in the copper-based alloy samples A to I according to the present invention, the wear scar width is smaller than in Comparative Examples J and K (conventional example). As described above, the wear resistance of the copper-based alloy of the present invention is improved as compared with the conventional one.

(Hard Particle Size Distribution) Sample C (Invention)
And the size of the hard particles (silicides and borides of Cr, Co, and Ni) of Sample K (Comparative Example, Cu-based alloy in JP-A-1-52232) were examined, and its size distribution was shown in FIG.
Shown in. Cr has a melting point (freezing point) of the boride of about 180.
It is as high as 0 ° C. and reacts preferentially with boron (B) during solidification of the hardfacing alloy to form boride. Since the solidification rate is extremely high in laser overlaying, the solidification ends without the large growth of the boride, so that many particles having a small particle size are formed. On the other hand, in the sample C containing Co, since the melting point of cobalt boride is relatively low (about 1000 ° C.),
There is sufficient time to allow two-phase separation in the liquid phase (time can be controlled) and large size particles can be crystallized. Therefore, as shown in FIG. 5, particles of large size are also formed with a gentle curve of size distribution.
In general, in order to secure the characteristics against abrasive wear, hard particles of a certain size are important in consideration of the hard particles of the mating material, and it is difficult to form hard particles of large size with a Cr-containing copper-based alloy. Therefore, it is considered difficult to secure wear resistance.

(Hardness of Hard Particles) Hard particles of sample C (invention) and sample J (comparative example, Cu-based alloy in Japanese Patent Application No. 63-157826) (Ni and Co silicides in sample C and Boride, Ni and Fe silicides and borides in sample J, and Vickers hardness (HV) of matrix
{9.8N}) was investigated and the result is shown in FIG. As can be seen from FIG. 6, the hardnesses of the Cu-based matrix portions of Samples C and J are almost the same, but the high temperature hardness of the hard particles is higher in Sample C than in Sample J. This is because the hardness of the hard particles of the sample C generated by the two liquid phase separation does not decrease much due to the high temperature, and the wear resistance is excellent especially when a high load is applied.

(Replacement of Co with Fe) In the present invention, a part of Co, which is an essential component, can be replaced with Fe.
The e substitution effect was investigated as follows. The copper-based alloy composition is Ni: 20 wt%, Si: 2.8 wt%, B: 1.3 wt%
%, Total of Co and Fe (constant): 10 wt%, balance C
As the u, the laser overlay described with reference to FIG. 1 was performed under the above-described conditions with the composition in which the amount of Fe was changed, and the overlay layer 8 was formed on the metal substrate 1. With the Ogoshi-type wear tester shown in FIG. No. 6 (alloy for build-up), a wear test was conducted under the above-described conditions to examine the wear scar width (wear resistance) and rotor weight loss (attacking property of the mating material) of the build-up layer, and the results are shown in FIG. As the amount of Fe increases in a constant total amount of Co and Fe (10%),
Abrasion resistance decreases, but opponent attacking property increases. Therefore, by defining the copper-based alloy composition in accordance with the mating material, it is possible to form a built-up layer having more appropriate wear characteristics including mating aggressiveness and wear resistance.

[0033]

As described above, the dispersion-strengthened Cu-based alloy according to the present invention is more excellent in wear resistance in a high temperature state than ever before. Since the Cu-based alloy of the present invention can be optionally overlaid (welded) on a metal substrate, it can be formed only on the parts of various mechanical parts (including engine valve seats) that require wear resistance. It is possible to improve the characteristics.

[Brief description of drawings]

FIG. 1 Laser overlaying (welding) of a Cu-based alloy on a metal substrate
It is a schematic perspective view of the apparatus which shows the method.

FIG. 2 is a metallographic photograph (× 400) of a dispersion strengthened Cu-based alloy overlay layer of Sample C according to the present invention.

FIG. 3 is a schematic view schematically showing an Ogoshi-type wear tester.

FIG. 4 is a graph showing wear test results.

FIG. 5 is a graph showing the distribution of hard particle size of samples C and K.

FIG. 6 is a graph showing hardness of hard particles and a matrix of Samples C and K.

FIG. 7 is a graph showing the influence of the Fe amount on the wear scar width and rotor weight loss in the copper-based alloy of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Metal substrate 2 ... Powder 4 ... Laser light 8 ... Overlay layer (welding layer) 10 ... Rotor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiko Mori 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor Masahiro Nakagawa 1 Toyota Town, Aichi Prefecture, Toyota Motor Corporation ( 72) Inventor Hiroyuki Murase 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor Minoru Kawasaki 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation, (72) Inventor, Taku Saito Aichi Prefecture Inside the Toyota Central Research Institute Co., Ltd. at 41 Nagamute, Nagakute-machi, Aichi-gun (72) Inventor Koji Tanaka Inside the Toyota Central Research Institute at 41-City, Nagakute-machi, Nagakute-cho, Aichi-gun, Aichi

Claims (3)

[Claims] 1. The following composition: Ni: 5 to 30.0 wt% Si: 0.5 to 5.0 wt% B: 0.5 to 3.0 wt% Co: 2 to 30 wt% (however, of these alloy components The total amount does not exceed 60 wt%) Cu and unavoidable impurities: A hardfacing copper-based alloy consisting of the balance and excellent in wear resistance. 2. The following composition: Ni: 5 to 30.0 wt% Si: 0.5 to 5.0 wt% B: 0.5 to 3.0 wt% Co and Fe: 2 to 30 wt% (however,
Co ≧ 2 wt%) (However, the total of these alloy components does not exceed 60 wt%) Cu and inevitable impurities: A hardfacing copper-based alloy with excellent wear resistance consisting of the balance. 3. The hardfacing copper-based alloy according to claim 1, which contains one or more of high melting point carbides, Pb, Sn and Zn.