JPS60177107A - Method for forming surface layer having different coefficient of thermal expansion on metallic member - Google Patents

Abstract

PURPOSE:To form a surface layer having the coefft. of linear expansion different from the coefft. of linear expansion of a base body without generating positional shift and exfoliation by adhering a powder alloy sheet onto a metallic member via a sheet having the coefft. of linear expansion at the intermediate of both materials and sintering the same by heating. CONSTITUTION:An intermediate powder alloy sheet 2 and a front side powder alloy sheet 3 are successively adhered to the surface of a metallic member 1. The sheet 3 is of the material meeting the intended function. The alloy powder having the coefft. of thermal expansion at the intermediate of the front side alloy powder and the member 1 is used for the sheet 2. Such adhered body A is heated to a prescribed sintering temp. to form a product a' laminated with the intermediate metallic layer 2' and a surface sintered metallic layer 3' on the surface of the member 1. The difference in the coefft. of thermal expansion between the member 1 and the sheet 3 is effectively lessened by the sheet 2 in such method and therefore the product having good dimensional accuracy and adhesion is obtd.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a method for forming a surface sintered metal layer on the surface of a metal member, which has a coefficient of thermal expansion different from that of the metal member and has a predetermined objective function. It's about how to do it.

(Prior art) A surface sintered metal layer having a predetermined function such as wear resistance or corrosion resistance is formed on the surface of a metal member. It has been put into practical use to form a compacted metal layer by a so-called powder alloy sheet method. In other words, in this powder alloy sheet method, a powder alloy sheet is formed by kneading alloy powder corresponding to the above-mentioned desired function with a resin binder, and after this powder alloy sheet is adhered to the surface of a metal member, this adhesive body is By heating, a sintered metal layer made of the alloy powder is formed on the surface of the metal member.

However, the coefficient of thermal expansion of a sintered metal layer having such a predetermined function is often significantly different from that of the metal member, and therefore, when used in a high-temperature area, A type of bimetal phenomenon due to a large difference in expansion coefficients causes defects such as the sintered metal layer peeling off from the metal member or cracking. Furthermore, when forming a sintered metal layer using the powder alloy sheet method described above, the powder alloy sheet may be misaligned with respect to the metal member due to a large difference in thermal expansion coefficient during heating, resulting in a failure to maintain the specified dimensional accuracy. In some extreme cases, the powder alloy sheet may be partially peeled off from the metal member, and cracks or pinballs may occur in the joint between the obtained sintered metal layer and the metal member, causing the joint to fail. This resulted in drawbacks such as incompleteness (weakened strength).

(Object of the invention) The present invention has been made in consideration of the above circumstances, and
Of course, it is possible to avoid problems such as cracks caused by the difference in thermal expansion coefficient between the obtained sintered metal layer and the metal member,
In particular, when forming a sintered metal layer using the powder alloy sheet method, surfaces with different thermal expansion coefficients are used on metal members to eliminate misalignment of the powder alloy sheet and imperfections in bonding due to differences in thermal expansion coefficients. The object is to provide a method for forming layers.

(Structure of the Invention) In the present invention, a large difference in the coefficient of thermal expansion between the metal member and the alloy powder corresponding to the intended function is buffered by the alloy powder having a coefficient of thermal expansion between the two. This is based on the conventional powder alloy sheet method, in which the intermediate alloy powder for IIl is also kneaded with a resin binder to form a sheet.

Specifically, in addition to the front side powder alloy sheet made by kneading the front side alloy powder corresponding to the intended function with a resin binder,
An intermediate powder alloy sheet is prepared by kneading with a resin binder an intermediate alloy powder having a thermal expansion coefficient intermediate between that of the surface-side alloy powder and that of the metal member. After adhering the above-mentioned intermediate powder alloy sheet to the surface of the intermediate powder alloy sheet and adhering the above-mentioned front-side powder alloy sheet to the surface of the intermediate powder alloy sheet, by heating these bonded bodies, the above-mentioned intermediate powder is applied to the surface of the metal member. This is to obtain a laminate of an intermediate sintered metal layer corresponding to the alloy sheet and a surface sintered metal layer corresponding to the front powder alloy sheet.

(Example) In FIG. 1, 1 is a metal member, and an intermediate powder alloy sheet 2 is adhered to the surface of this metal member 1, and a front side powder alloy sheet 3 is adhered to the surface of the intermediate powder alloy sheet 2. . The intermediate powder alloy sheet 2 and the front powder alloy sheet 3 are each made of a kneaded mixture of alloy powder and a resin binder, and the alloy powder of the front powder alloy sheet 3 located on the outermost side, that is, the front alloy powder is a wear-resistant alloy powder that corresponds to a predetermined objective function on the surface of the metal member l, that is, if the objective function is wear resistance, for example,
Moreover, if it is corrosion resistant, it is considered as a corrosion resistant alloy powder. Further, the alloy powder of the intermediate powder alloy sheet 2 located in the middle, that is, the intermediate alloy powder, has a thermal expansion coefficient that is intermediate between the thermal expansion coefficient of the surface side alloy powder and the thermal expansion coefficient of the metal member l. It is said that Therefore, since this intermediate alloy powder is not intended for obtaining a predetermined objective function, it is possible to appropriately adopt a wide range of materials depending on the intended use of the product.

If the bonded body A of the metal member l, the intermediate powder alloy sheet 2, and the front powder alloy sheet 3 as described above is heated at a predetermined sintering temperature, as shown in FIG. A product A' is obtained in which the intermediate sintered metal layer 2' and the surface sintered metal layer 3' are laminated. Of course, the surface sintered metal layer 3' corresponds to the surface side powder alloy sheet 3 and is located on the outermost side, and the intermediate sintered metal layer 2' corresponds to the intermediate powder alloy sheet 2 and is located on the outermost side of the metal member 1. and the surface sintered metal layer 3'.

In order to clearly separate (physically separate) the metal member 1 and the surface sintered metal layer 3', it is preferable that the intermediate sintered metal layer 2' be solid phase sintered. While using an alloy powder having a melting point higher than that of the surface side alloy powder, heating for sintering may be performed at a temperature below the melting point of the intermediate alloy powder (of course, sintering of the surface side alloy powder In addition, if mechanical strength is particularly required due to the application of a large external force to the surface of the surface sintered metal layer 3', at least a portion of the surface alloy powder may be in a liquid phase. It is sufficient to heat it at a sintering temperature that makes it a semi-liquid phase (the intermediate alloy powder may also be made to become a semi-liquid phase).
In this case, the intermediate alloy powder should be selected to have poor wettability to the surface alloy powder.Of course, the heating atmosphere may be a non-oxidizing atmosphere such as vacuum, N2 gas, N2 gas, etc. Preferably, it is an atmosphere.

Here, as the adhesive body, as shown in the third JiWB,
A plurality of intermediate powder alloy sheets 2, ie, code 2-1.2
-2.2-3 may also be used. In this case, the resulting product B' will be as shown in FIG. 4, but each individual layer 2 of the intermediate powder alloy sheet 2 -1.2
-2. The thermal expansion coefficient of the intermediate alloy powder in 2-3 gradually increases from the metal member l to the surface sintered metal layer 3' (the surface side alloy powder of the surface side powder alloy sheet 3). . That is, if each thermal expansion coefficient is α for the metal member 1, β for the individual layer 2-1, γ for the individual layer 2-2, and δ for the individual layer 2-3, ε for the surface-side alloy powder, then α>β 〉γ〉δ〉 (or α〉β〉γ〉δ〉). In this way, the difference in thermal expansion coefficient between the metal member l and the surface side alloy powder (surface sintered metal layer 3') Even if the coefficient of thermal expansion is extremely large, this difference in coefficient of thermal expansion can be effectively buffered step by step.

The above-mentioned adhesion between the metal member 1, the intermediate powder alloy sheet 2, and the front powder alloy sheet 3 is achieved by this self-adhesion when at least the intermediate powder alloy sheet 2 located in the middle has self-adhesiveness due to its resin binder. The three parts 1, 2, and 3 can be bonded as is without using a separate adhesive by taking advantage of their self-adhesive properties, but if they do not have this self-adhesive property, use a separate adhesive (double-sided adhesive tape). including)
Also, the order of bonding the metal member 1, the intermediate powder alloy sheet 2, and the front powder alloy sheet 3 is not particularly important. It is preferable that the intermediate powder alloy sheet 2 and the front powder alloy sheet 3 are bonded together in advance to form one sheet. In order to obtain such a laminated sheet of the intermediate powder alloy sheet 2 and the front powder alloy sheet 3, the intermediate powder alloy sheet 2 and the front powder alloy sheet 3, which are separately prepared in advance, are passed between a pair of rolls, for example. They may be bonded together by pressing them together; in this case, if the intermediate powder alloy sheet 2 or the front powder alloy sheet 3 has self-adhesive properties due to the resin binder, they will be bonded to each other simply by the pressing described above. Furthermore, if the material does not have this self-adhesive property, adhesion may be used separately.

Various metal members can be considered as the metal member to which the present invention is applied; for example, there is a chip piece of a rocker arm in an internal combustion engine. That is, in FIG. 5, the rocker arm C has a main body 4 made of a light metal such as an aluminum alloy, and a tip piece 6 made of steel, for example, is cast into one sliding end of the main body 4. The cam 5 of the chip piece 6
The sintered metal layer 7 (2', 2',
3') is formed. Of course, the present invention is not limited to the tip piece 6, but can be applied to other suitable parts such as the pressing end face of a tappet in an internal combustion engine.

Acrylic resin is preferably used as the resin binder for the intermediate powder alloy sheet 2 and the front powder alloy sheet 3. This acrylic resin alone has sufficient adhesiveness (tackiness) at room temperature, and even when used as a resin binder, this adhesiveness is maintained without causing carbonization or the like even at considerably high temperatures. Since gas is not generated rapidly and is diffused smoothly, so-called sheet bulges are less likely to occur. The acrylic resin used as the resin binder begins to turn into tar pitch at around 300°C, and the bonding force to the metal member 1 is gradually transferred from the resin to the tar pitch-like substance, and the powder alloy is sintered. A material having adhesion or bondability to the metal member 1 up to a temperature at which bonding starts can be obtained. That is, even if the bonded body of the metal member 1 and the powder alloy sheet 2.3 having an acrylic resin as a binder is subjected to some vibration while being transported and heated, the powder alloy sheet 2.3 Even when the powder alloy sheet 2.3 is adhered to an inclined surface (including a vertical surface) of the metal member 1, the powder alloy sheet 2 does not shift relative to the metal member 1. .3 does not fall off from the metal member 1 on the way, such an acrylic resin as a binder is 3% by volume to 15% by volume (alloy powder is 85% by volume).
Capacity%~97. In other words, if the acrylic resin is 3% by volume, it will be difficult to maintain the tackiness at room temperature and the flexibility of the powder alloy sheet;
If the amount is more than % by volume, the porosity of the obtained sintered metal is likely to be adversely affected and it becomes difficult to obtain sufficient bondability.

As is well known, the acrylic resin is a polymer or copolymer of acrylic esters or methacrylic esters, and any of these may be used.

Here, if the bonded body A or B is likely to be accompanied by particularly large vibrations during transportation, for example, if a mesh belt type, pusher-equipped continuous sintering furnace, vacuum sintering furnace, etc. are used, powder alloy sheet 2. In order to further strengthen the adhesion or bondability of No. 3 to the metal member 1,
It is preferable to proceed as follows, that is, after adhering the powder alloy sheet 2.3 to the metal member l with an acrylic resin adhesive,
It is recommended to hold the temperature at 350℃ for 5 minutes or more, and then raise the temperature to the sintering temperature.If you do this, the separately applied adhesive will evaporate from around 120℃, and the temperature will rise to around 200℃. A thermal decomposition polycondensation reaction occurs to generate a tar pitch-like substance, and the adhesive properties of this tar pitch-like substance firmly integrate the powder alloy sheet 2.3 and the metal member until the sintering temperature is reached. be done. In addition, if the temperature for obtaining the tar pitch-like substance is less than 150°C, the undecomposed amount will increase, which is undesirable. If the temperature is heated above 380°C, this undecomposed amount will rapidly decompose and be vaporized. This results in less tar pitch-like material being produced and insufficient adhesion. Furthermore, the optimum holding time varies depending on the heat treatment temperature, but if it is less than 5 minutes, the amount of tar pitch-like substances produced will be small and sufficient adhesion will not be obtained;
Retention for longer than 1 minute is unnecessary to ensure sufficient production of tar pitch-like material.

In addition, when acrylic resin is used as the resin binder and has self-adhesive properties, the same effect as described above can be obtained by holding the temperature at 150°C to 380°C for 5 minutes or more without using a separate adhesive. can be expected.

Furthermore, the heating rate up to the sintering temperature is 10℃/min ~
40°C/min is preferable, and it is particularly preferable to keep the temperature below 40°C/min until the temperature close to the end of thermal decomposition of the resin binder. evaporates rapidly, which is undesirable as it may damage the powder alloy sheet 2 or 3 or form bubbles on the adhesive surface, and it also makes it difficult for the liquid phase below the line (metallic liquid phase) to appear below 10°C/min. . In addition, the appearance ratio of this liquid phase is preferably 10% or more in consideration of bondability with metal members, and powder alloy sheet 2 or 3 is preferably 10% or more.
In order to maintain the morphology, it is preferably 50% or less.

Next, as for the alloy powder, it is preferable that the sintering temperature is low because there is a limit to the adhesiveness of the resin binder, and therefore it is better to use a eutectic alloy.And if the intended function is, for example, wear resistance, it is preferable to use a eutectic alloy. As the alloy powder of the front side powder alloy sheet 3, Fe-M-
It is preferable to use a C-based ternary eutectic alloy, and this Fe-
M in the MC system is preferably one of P, Mo, and H, or a composite thereof.

Further, it is preferable to add at least one of Cr, V and W to the Fe-M-C alloy powder as a secondary component.

Incidentally, the particle size of the alloy powder is a factor that greatly affects the porosity of the sintered layer, and it is preferable to use one with a fine particle size of 150 mesh or less.

Next, test examples of the present invention will be explained. First, to explain the case where the coefficient of thermal expansion of the metal member l is larger than the coefficient of thermal expansion of the surface sintered metal layer 3' (the front side alloy powder of the front side powder alloy sheet 3), the weight of the metal member l is % C2.8%, Si1.8%, Mn1.0%,
Ni2O%, Cr3.1%, Po, 08%, balance Fe
cy) composition (thermal expansion coefficient is 20
18,7X IO-'/''0) was used at a temperature of 200°C to 200°C.The surface side alloy powder of the surface side powder alloy sheet 3 contained 2.42% C and 8.50% Cr by weight.
, M o 4 , 24%, SiO, 45%, Pl, 05
%, the balance being Fe (thermal expansion coefficient: 12゜OXlO-6/''0 at 20℃~200℃)
), 91% by volume of the alloy powder and 9% by volume of the acrylic resin were kneaded with the addition of toluene as a solvent to form a surface-side powder alloy sheet 3 with a thickness of 1°5 mm.
was formed.

Furthermore, as the intermediate alloy powder of the intermediate powder alloy sheet 2, its weight percentage is C2.4%, Si5.5%, M n 0
, 9%, Cr5.0%, Po, 08%, balance F
Alloy powder with a composition consisting of e (thermal expansion coefficient is 20℃~20
0℃-C14,4 An intermediate powder alloy sheet 2 was formed.

The bonded body of the metal member 1, the intermediate powder alloy sheet 2, and the front powder alloy sheet 3 was heated for 300 minutes in an H2 atmosphere.
After dewaxing for 30 minutes at 1050°C in a vacuum atmosphere
Sintering was performed for 30 minutes. As a result, the intermediate powder alloy sheet 2 and the front powder alloy sheet 3
No bonding defects such as misalignment or peeling of (the intermediate sintered metal layer 2' and the surface sintered metal layer 3') were observed, and the bonding was good.

Next, the coefficient of thermal expansion of the metal member l is determined by the surface sintered metal layer 3'.
To explain the case where the coefficient of thermal expansion is smaller than the coefficient of thermal expansion of the metal member l
A steel material consisting of 0.25% by weight of C, 0.6% by weight of Mn, and the balance Fe (thermal expansion coefficient of 13-IXIO-6/''C at 20°C to 300°C) was used as the material, and a powder alloy sheet on the surface side was used. As the alloy powder on the surface side of No. 3, 70% by weight of Cu
, an alloy powder having a composition of 30% by weight of Zn (25°C ~ 3% by weight)
Using a thermal expansion coefficient of 19.9XlO/"0) at 00°C, toluene as a solvent was added to 91% by volume of the alloy powder having such a composition and 9% by volume of the acrylic resin and kneaded. 1. A surface-side powder alloy sheet 3 with a thickness of 5 mm was formed.Furthermore, as an intermediate alloy powder of the intermediate powder alloy sheet 2, an alloy powder (thermal expansion at 25°C to 300°C) having a composition of Cu9B weight % and Be 2.0 weight% The coefficient is 16.7Xl
Using O-6/"C alloy powder 91 with such a composition
Toluene as a solvent was added to 9% by volume of the acrylic resin and 9% by volume of the acrylic resin to form a surface-side powder alloy sheet 3 having a thickness of 1.5 mm. The bonded body of the metal member 1, the intermediate powder alloy sheet 2, and the front powder alloy sheet 3 was dewaxed at 300°C for 30 minutes in an Ht atmosphere, and then heated at 900°C for 30 minutes.
When sintering was performed for a minute, it was found that the intermediate powder alloy sheet 2 and the front powder alloy sheet 3 (intermediate sintered metal layer 2' and front sintered metal layer 3') were misaligned or peeled off with respect to the metal member l. No bonding defects were observed, and the bonding was good.

(Effects of the Invention) As is clear from the above description, the present invention provides a metal member and a surface-side powder alloy sheet (
Even if there is a large difference in thermal expansion coefficient from that of the surface-side powder alloy sheet (alloy powder), the intermediate powder alloy sheet (intermediate powder alloy sheet) containing an intermediate alloy powder having an intermediate thermal expansion coefficient The difference in thermal expansion coefficients is effectively buffered by the alloy powder), so that a good bonding can be performed without causing any displacement or peeling of the sheets during sintering. As a result, not only can we obtain high-quality products with good dimensional accuracy and bonding, but it has also become possible to use alloy powders with large differences in thermal expansion coefficients for metal parts. This greatly expands the scope of application of this type of powder alloy sheet method, in other words, the scope for selecting the alloy powder to provide a predetermined desired function to the back surface of the metal member.

Of course, even if the obtained product is used at high temperatures, there is a thermal expansion coefficient between the surface sintered metal layer and the metal member that has a predetermined purpose function. Since the intermediate sintered metal layer is present, cracks in the surface sintered metal layer due to the so-called bimetal phenomenon are prevented, and the temperature range of the product itself can be expanded.

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views showing steps in an embodiment of the present invention. FIGS. 3 and 4 are cross-sectional views showing steps in another embodiment of the present invention. FIG. 5 is a side view of a rocker arm provided with a chip piece as a metal member to which the present invention is applied. 1...Metal member 2...Intermediate powder alloy sheet 3...Front side powder alloy sheet 2'...Intermediate sintered metal layer 3'...Surface sintered metal layer A, B... ...Adhesive body A", B'...Product

Claims (1)

[Scope of Claims] (1) A method for forming a surface sintered metal layer on the surface of a metal member, which has a coefficient of thermal expansion different from that of the metal member and has a predetermined objective function, , a front-side powder alloy sheet formed by kneading a front-side alloy powder corresponding to the objective function with a resin binder, and a thermal expansion coefficient intermediate between the thermal expansion coefficient of the front-side alloy powder and the thermal expansion coefficient of the metal member. An intermediate powder alloy sheet is prepared by kneading an intermediate alloy powder with a resin binder, and the intermediate powder alloy sheet is adhered to the surface of the metal member, and the surface side powder a step of bonding an alloy sheet; heating the bonded body of the metal member, the intermediate powder alloy sheet, and the front side powder alloy sheet to apply an intermediate sintered metal corresponding to the intermediate powder alloy sheet on the surface of the metal member; A method for forming a surface layer having a different coefficient of thermal expansion on a metal member, the method comprising the step of obtaining a laminate of the layer and the surface sintered metal layer corresponding to the surface side powder alloy sheet. (2. In claim 1, the intermediate alloy powder has a higher melting point than the surface side alloy powder, and the heating temperature is set to a temperature equal to or lower than the melting point of the intermediate alloy powder, The intermediate sintered metal layer is solid-phase sintered. (3) In claim 1 or 2, the intermediate sintered metal layer is a plurality of layers, that is, the intermediate powder alloy sheet is a plurality of intermediate powder alloy sheets. (4) Claims No. Any one of paragraphs 1 to 3
In item 1, the resin binders of the front side powder alloy sheet and the intermediate powder alloy sheet are each made of acrylic resin. (5) In claim 4, the intermediate powder alloy sheet includes 3 to 15 volume % of acrylic resin as the resin binder and 85 to 97 volume % of the intermediate alloy powder.
The intermediate powder alloy sheet is bonded to the metal member and the front powder alloy sheet is bonded to the intermediate powder alloy sheet by self-adhesiveness due to the adhesiveness of the acrylic resin as the resin binder. What I did. (5) In claim 5, the front side powder alloy sheet has an acrylic resin as the resin binder of 3 to 15% by volume and a front side alloy powder of 85 to 97% by volume, and the resin Self-adhesive due to the adhesiveness of acrylic resin as a binder. (6) Any one of claims 1 to 5
In Item 1, the front powder alloy sheet and the intermediate powder alloy sheet are a single laminated sheet that is bonded in advance before being bonded to the metal member.