JPH06346166A - Ni-based powder sintered alloy excellent in weldability and composite valve rod - Google Patents

Abstract

PURPOSE:To produce a Ti-Al-Cr-Ni type Ni-based powder sintered alloy excellent in heat and corrosion resistance and having satisfactory weldability and to provide a composite valve rod whose lining layer is hardly cracked at the time of repair by build-up welding and is less liable to peeling from the body. CONSTITUTION:Heat and corrosion resistant Ti-Al-Cr-Ni alloy powder is press- sintered by hot isostatic pressing, densified and integrated to obtain the objective Ni-based powder sintered alloy contg. >=85ppm O2 and/or 0.2-1.5wt.% Hf. A lining layer made of the sintered alloy is formed on the body of a valve rod made of a heat resistant alloy from the bottom of the bevel part to the top of the peripheral edge part and this lining layer is joined to the body with an Ni plating layer in-between to obtain the objective composite valve rod.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Ni-based powder sintered alloy having excellent heat resistance, corrosion resistance and weldability, and a composite valve rod having a lining layer formed of the powder sintered alloy.

[0002]

2. Description of the Related Art A valve rod provided with an umbrella portion for opening and closing an intake hole and an exhaust hole opened in a combustion chamber of an internal combustion engine is required to have heat resistance and corrosion resistance at high temperatures, and conventionally, Ti having such characteristics is used. It was forged by a -Al-Cr-Ni heat resistant corrosion resistant alloy, for example, Nimonic 80A.

However, since a forged valve rod made of a Ti-Al-Cr-Ni heat-resistant and corrosion-resistant alloy is expensive, in recent years, Japanese Patent Application No.
As disclosed in No. 146999, composite valve rods have been used in which only a portion requiring high temperature characteristics is covered with a lining layer made of a sintered material of heat-resistant and corrosion-resistant alloy powder. That is, in the composite valve rod, in order to form a lining layer from the lower surface (touch surface) of the umbrella portion exposed to high temperature to the seat surface of the umbrella portion that abuts the intake / exhaust hole openings, the valve stem main body is made of austenite or Forged using martensitic heat-resistant stainless steel, nickel heat-resistant alloy, etc., along the upper surface of the peripheral portion from the lower surface of the umbrella portion of the valve rod body, Ti-Al
-Cr-Ni heat-resistant and corrosion-resistant alloy powder layer is arranged, the powder layer is sintered by hot isostatic pressing (HIP), and a lining layer made of the sintered material is joined to the valve stem body. is there.

[0004]

Although the above-mentioned compound valve rod has the desired quality and is excellent in economic efficiency, when it is used for a long period of time, it is localized on the seat surface that repeatedly contacts the valve seat. A hollow appears. This depression is usually repaired by overlay welding using a Ni-base or Co-base alloy having excellent heat resistance and corrosion resistance.

However, T such as Nymonic 80A
The i-Al-Cr-Ni heat-resistant and corrosion-resistant alloy powder sintered material has low ductility, and the shrinkage stress of the welded portion easily causes cracks in the heat-affected zone, resulting in poor weldability. In addition, due to the expansion and contraction of the base material and the lining layer due to the heat at the time of welding overlay, thermal stress acts on the HIP joint interface, the joint interface of the lining layer cannot withstand the thermal stress, and the upper surface of the umbrella portion and the main body are lined. There is a problem that the interface with the layers opens.

The present invention has been made in view of the above problems, and Ti having excellent heat resistance and corrosion resistance and good weldability is also used.
-Al-Cr-Ni-based Ni-based powder sintered alloy, and a composite valve rod in which cracks are unlikely to occur in the lining layer during repair by welding overlay and the lining layer does not easily separate from the main body And

[0007]

The Ni-based powder-sintered alloy of the present invention comprises a Ti-Al-Cr-Ni heat-resistant and corrosion-resisting alloy powder which is pressure-sintered by hot isostatic pressing to form a densely integrated body. Ni
It is a base powder sintered alloy and has an O ₂ content of 85 ppm or less. In the same alloy, Hf is 0.2 to 1.5.
wt% (hereinafter, simply%) is included. Further, the O ₂ content is set to 85 ppm or less, and Hf is contained at 0.2 to 1.5%.

The composite valve rod of the present invention is made of a Ti-Al-Cr-Ni-based material by hot isostatic pressing from the lower surface of the umbrella portion of the valve rod body made of a heat-resistant alloy to the upper surface of the peripheral edge portion. In a composite valve rod in which the heat-corrosion-resistant alloy powder is pressure-sintered to form a lining layer and the lining layer is joined,
The lining layer is formed of the above Ni-based powder sintered alloy, and the lining layer is joined via a Ni plating layer.

[0009]

Function Ti strengthened by precipitation of the γ'phase (Ni ₃ [Al, Ti]) as typified by Nimonic 80A
In the case of a -Al-Cr-Ni heat-resistant corrosion-resistant alloy, it is said that welding is difficult even with a forged material because the ductility is extremely lowered in the vicinity of the precipitation temperature of the γ'phase of 800 ° C.

In the case of the powder sintered alloy, the fragile powder grain boundary resulting from the oxide film formed on the surface of the powder during the production of the powder and the extremely brittle carbide formed around the oxide film as the nucleus is the HIP and the heat treatment. It remains in the later sintered alloy. When welding is performed on such a Ti-Al-Cr-Ni-based powder sintered alloy, the matrix of the powder is precipitated and hardened by the welding heat, the ductility is lowered, and a fragile powder grain boundary is formed. When an external force such as a contracting force is applied, it easily separates and breaks at the powder grain boundaries.

In the present invention, since the O ₂ content in the Ti-Al-Cr-Ni-based powder sintered alloy is suppressed, it is difficult for the oxide film to remain at the powder grain boundaries, and the oxide film is formed by using the oxide film as a nucleus. The brittle carbide content becomes too small, the ductility is improved, and the weldability is improved. When the O ₂ content exceeds 85 ppm,
The ratio of the powder in which the oxide film is formed on the surface of the powder particles in the raw material powder is rapidly increasing, and many fragile powder grain boundaries are left in the sintered material after HIP and heat treatment, resulting in ductility. descend.

In the present invention, Ti-Al-Cr-Ni is used.
Since Hf is contained in the system powder sintered alloy, it is difficult for oxide films and carbides to remain at the powder grain boundaries, and ductility is improved. Hf has an action of diffusing O ₂ at the powder grain boundaries into grains, and has an action of suppressing the formation of oxide films and carbides at the powder grain boundaries and improving ductility. If it is less than 0.2%, the effect is too small, while if it exceeds 1.5%, the effect of improving ductility is saturated, which is disadvantageous in terms of cost.

In the present invention, the O ₂ content is 85 pp.
When the Hf content is 0.2 to 1.5% to m or less, the actions of both are combined to exert an excellent action of suppressing oxide films and carbides, and high ductility can be obtained. On the other hand, the joint interface between the valve stem body and the lining layer of the conventional composite valve stem is
Due to the diffusion of O ₂ and C, oxides and carbides such as Ti, Cr and Al are deposited, so that the bonding strength is low and the ductility is poor.

In the composite valve rod of the present invention, the Ni plating layer is present at the joint interface. Since Ni has a small atomic radius,
It has an effect of suppressing diffusion of O ₂ and C. Therefore, T
Precipitation of oxides and carbides such as i, Cr and Al can be suppressed, and as a result, the bonding strength at the HIP bonding interface,
Ductility is improved. In addition to Ni, Pt, Zn, and Cd have the same action, but Pt is expensive, Zn is useless because of its low melting point, and Cd is unsuitable for environmental hygiene. Is.

[0015]

EXAMPLES The Ni-based powder sintered alloy of the present invention is Ti
-Al-Cr-Ni system is resistant corrosion resistant alloy powder HIP sintering material, O _2: 85 ppm or less, or, and Hf: 0.2
However, other components may be at least Cr: 18 to 21%, Ti and Al, and precipitate a γ'phase. The mnemonic 80A and the mnemonic 90 can be exemplified.・ Nymonic 80A composition C: 0.10% or less, Si: 1.0% or less, C
u: 0.2% or less, Fe: 3.0% or less, Mn:
1.0% or less, Cr: 18.0 to 21.0%, Ti: 1.8
~ 2.7%, Al: 1.0-1.8%, Co: 2.0
% Or less, B: 0.008% or less, Zr: 0.15% or less, Pb: 0.0025% or less, S: 0.015% or less, balance: Substantially Ni / Nymonic 90 composition C: 0.13% or less, Si: 1.0% or less, C
u: 0.2% or less, Fe: 1.5% or less, Mn:
1.0% or less, Cr: 18.0 to 21.0%, Ti: 2.0
~ 3.0%, Al: 1.0-2.0%, Co: 15.0-21.
0% or less, B: 0.020% or less, Zr: 0.15% or less, Pb: 0.0020% or less S: 0.015% or less, balance: Melting alloy of composition A substantially corresponding to Ni mnemonic 80A under various atmospheres However, various O ₂ gas is produced by the gas atomizing method.
A powder having a content was produced and sintered by HIP to a substantially true density. Tensile test pieces were taken from the obtained powder sintered alloy material, and the relationship between elongation and the O ₂ content in the sintered alloy was examined by a room temperature tensile test. The result is shown in FIG. From the figure, the O ₂ content according to the example is 85 ppm.
It can be seen that the following materials have an elongation of 20% or more and are extremely excellent in ductility.

Further, based on the alloy of the composition A and the composition B corresponding to Nymonic 90, various amounts of Hf are added to the alloy to melt in the air, and the resulting molten metal is atomized in an oxygen-free atmosphere to form a Ni-based alloy. An alloy powder was produced. The powder is sintered by HIP to obtain a powder sintered material (O ₂ content: 15
0 ppm) was produced, and a tensile test piece was sampled from this to investigate the relationship between elongation and Hf content. The results are shown in FIG. From the same figure, even when dissolved in the atmosphere, when the Hf content is 0.2% or more, the elongation can be secured 10% or more, and improvement of the weldability is expected as compared with the conventional example containing no Hf. . In the figure, ● corresponds to the base alloy composition A and ▲ corresponds to the base alloy composition B.

Further, based on the alloys of the above-mentioned composition A and composition B, Hf was added thereto and vacuum-melted, and the obtained molten metal was atomized in an oxygen-free atmosphere to produce a Ni-based alloy powder, and HIP was used. The sintered material (O ₂ content: 70
Elongation at normal temperature and high temperature was examined by a tensile test using ppm and Hf content: 0.5%). The result is shown in Figure 3.
Shown in. For comparison, a sample was manufactured under the same conditions except that Hf was not dissolved in the atmosphere, and the same test was performed. The results are also shown in FIG. In the figure, ○ and △ are vacuum melting materials, ● and ▲ are atmospheric melting materials, ○ and ● correspond to the base alloy composition A, and △ and ▲ correspond to the base alloy composition B. From the figure, it can be seen that the low O ₂ content and the Hf content (◯ / Δ) according to the example significantly improve the elongation as compared with the conventional example (● / ▲).

Next, the actual weldability of the material of the present invention was investigated.
The sample manufacturing procedure and test procedure are as follows. Based on the alloys of the above compositions A and B, various melting conditions and Hf addition amounts were adjusted to obtain various O ₂ content and Hf content Ni.
A base alloy was melted, atomized in an oxygen-free atmosphere using the molten alloy, and the obtained powder was sintered to a substantially true density by HIP to form a 100 × 100 × 40 mm thick material block. Then, on the surface thereof, a weld rod of Stellite No. 6 was used to perform overlay welding so that the beads were drawn in a circle, and after completion of welding, it was examined by dyeing flaw detection whether or not cracks were generated around the beads and in the cross section. The results are shown in Table 1. The overlapping state of the beads is as shown in FIG. 4, and the numbers in the figure indicate the weld beads formed in the same pass order. In Table 1, O ₂ · H
The f content is an analysis value in the sintered material, and is sample No. 1 to
5, 8-12 correspond to an Example. Others are conventional examples.

[0019]

[Table 1]

From Table 1, in Examples (Nos. 1, 3, 8, 10) in which both the O ₂ content and the Hf content are within the range of the present invention, no cracks were generated even after performing 4-pass welding. . on the other hand,
In the examples in which the O ₂ content is within the range of the present invention (Nos. 5, 12) and the examples in which the O ₂ content is outside the range of the present invention include a predetermined amount of Hf (Nos. 2, 4, 9, 11), There is no cracking in the 1st or 2nd pass, which shows that it is effective for slight welding such as partial repair.

The Ni-based powder sintered alloy described above is suitable as a lining material for a composite valve rod. In the present invention, when the lining layer made of the Ni-based powder sintered alloy is formed on the composite valve rod, the surface of the valve rod main body covering the lining layer, that is, from the lower surface of the umbrella portion of the valve rod main body to the peripheral surface upper surface The Ni plating layer is formed in advance. The thickness of the Ni plating layer is preferably about 50 to 80 μm. If the thickness is less than 50 μm, the elongation is not sufficiently improved, so the lower limit is preferably about 50 μm. On the other hand, even if it exceeds 50 μm, further improvement in tensile strength and elongation cannot be expected, and the upper limit is preferably set to about 80 μm in consideration of variations in industrial production. Incidentally, FIG. 5 is a graph showing the relationship between the thickness of the Ni plating layer and the mechanical properties of the joint.
(Corresponding to H31) is coated with a Ni plating layer having various layer thicknesses, and HIP is used to interpose Nimonic 80A through the Ni plating layer.
The powder sintered alloy layers are joined together. As is clear from the figure, it can be seen that good bonding can be obtained at 50 μm or more.

Next, as shown in FIG. 6, a composite valve rod for marine low-speed diesel engine (dimension surface 450 mm in diameter) was manufactured, and after heat treatment, weldability was tested. The composite valve rod is manufactured by forging the valve rod main body 5 with austenitic heat-resistant steel (SNCrW) and performing Ni plating with a thickness of 50 μm along the lining layer joining surface of the main body 5, that is, from the lower surface of the umbrella portion 6 to the peripheral upper surface. A layer (not shown) is formed, a capsule is attached so as to cover the joint surface, and a mnemonic 8 having an O ₂ content of 72 ppm and a Hf content of 0.5% is provided between the joint surface and the capsule.
After filling 0A alloy powder and degassing the gas in the powder filling space from the degassing tube provided in the capsule, 1000 ° C., 110
HIP treatment was performed at 00 kgf / cm ² , and the powder was sintered to form the lining layer 7 and joined. The O ₂ and Hf contents of the lining layer 6 after sintering were substantially the same as those of the powder.

The welding test was conducted at a depth of 5 on the seat surface of the composite valve rod.
mm concave portion, and while applying residual heat of 300 to 350 ° C. to the concave portion, using a welding rod of Stellite No. 6, TIG
After four-layer overlay welding by welding to form a bead 8 having a width of 25 mm and a depth of 5 mm, the HIP bonding interface near the bead and the upper surface of the umbrella portion were examined by a dye flaw detection test.
As a result, neither cracking nor peeling was observed in the bead portion, its vicinity, and the bonding interface. Also, a test piece 9 including the same HIP joint interface was cut out by wire cutting, and 40
When observed under a microscope at 0 ×, the HIP joint interface was completely adhered. Further, the surface analysis of the HIP bonding interface by EPMA did not detect the precipitation of oxides or carbides such as Ti, Cr and Al.

The Ni-based powder sintered alloy of the present invention can be used not only as a lining material for the above-mentioned valve rod but also in various fields where heat resistance and corrosion resistance are required, such as fuel injection valves and cylinders. Of course.

[0025]

As described above, the Ni-based powder-sintered alloy of the present invention is obtained by press-sintering Ti-Al-Cr-Ni heat-resistant and corrosion-resistant alloy powder by hot isostatic pressing to obtain a dense integrated body. Ni-based powder sintered alloy, which has been converted to an O ₂ content of 85 ppm.
Since it is suppressed to the following or / and Hf is contained in an amount of 0.2 to 1.5%, it is difficult for the oxide film to remain at the powder grain boundaries, and the amount of brittle carbides generated with the oxide film as the nucleus is too small.
Ductility is increased and weldability is improved. Especially the O ₂ content is 8
By setting the Hf content to 0.2 to 1.5% in an amount of 5 ppm or less, the effects of both are combined to exert an excellent effect of suppressing oxide films and carbides, and to obtain high ductility and excellent weldability. You can

Further, in the composite valve rod of the present invention, since the lining layer is formed of the Ni-based powder sintered alloy and is joined to the valve rod body through the Ni plating layer, the surface of the lining layer is built up. When repairing by welding, it is possible to prevent the occurrence of weld cracks, improve the strength and ductility at the joint interface, and prevent the lining layer from peeling due to thermal stress during welding.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between O ₂ content and elongation in a Ti—Al—Cr—Ni-based powder sintered alloy.

FIG. 2 is a graph showing the relationship between Hf content and elongation in a Ti—Al—Cr—Ni-based powder sintered alloy.

FIG. 3 shows Ti—Al—Cr— according to examples and conventional examples.
3 is a graph showing the relationship between tensile test temperature and elongation in a Ni-based powder sintered alloy.

FIG. 4 is an explanatory cross-sectional view showing a build-up state in a welding test.

FIG. 5 is a graph showing the relationship between the Ni plating layer thickness and the mechanical properties of the joint.

FIG. 6 is a cross-sectional view of an essential part of a composite valve rod, which has been welded and built up on a seat surface of an umbrella portion, which has been subjected to a welding test.

[Explanation of symbols]

 1-4 Welding bead 5 Valve stem body 6 Umbrella part 7 Lining layer

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 19, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

[0015]

EXAMPLES The Ni-based powder sintered alloy of the present invention is Ti
-Al-Cr-Ni system is resistant corrosion resistant alloy powder HIP sintering material, O _2: 85 ppm or less, or, and Hf: 0.2
However, other components may be at least Cr: 18 to 21%, Ti and Al, and precipitate a γ'phase. The mnemonic 80A and the mnemonic 90 can be exemplified.・ Nymonic 80A composition C: 0.10% or less, Si: 1.0% or less, C
u: 0.2% or less, Fe: 3.0% or less, Mn:
1.0% or less, Cr: 18.0 to 21.0%, Ti: 1.8
~ 2.7%, Al: 1.0-1.8%, Co: 2.0
% Or less, B: 0.008% or less, Zr: 0.15% or less, Pb: 0.0025% or less, S: 0.015% or less, balance: Substantially Ni / Nymonic 90 composition C: 0.13% or less, Si: 1.0% or less, C
u: 0.2% or less, Fe: 1.5% or less, Mn:
1.0% or less, Cr: 18.0 to 21.0%, Ti: 2.0
~ 3.0%, Al: 1.0 to 2.0%, Co: 15.0 to 2
1.0% , B: 0.020% or less, Zr: 0.15% or less, Pb: 0.0020% or less S: 0.015% or less, balance: Ni alloy of composition A corresponding to Ni Nimonic 80A is substantially melted under various atmospheres. , Various O ₂ by gas atomizing method
A powder having a content was produced and sintered by HIP to a substantially true density. Tensile test pieces were taken from the obtained powder sintered alloy material, and the relationship between elongation and the O ₂ content in the sintered alloy was examined by a room temperature tensile test. The result is shown in FIG. From the figure, the O ₂ content according to the example is 85 ppm.
It can be seen that the following materials have an elongation of 20% or more and are extremely excellent in ductility.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

Further, based on the alloy of the composition A and the composition B corresponding to Nymonic 90, various amounts of Hf are added to the alloy to melt in the air, and the resulting molten metal is atomized in an oxygen-free atmosphere to form a Ni-based alloy. An alloy powder was produced. The powder was sintered by HIP to obtain a powder sintered material (O ₂ content: 13
0 to 170 ppm) was produced, and a tensile test piece was sampled from this to examine the relationship between elongation and Hf content. The results are shown in FIG. From the same figure, even when dissolved in the atmosphere, when the Hf content is 0.2% or more, the elongation can be secured 10% or more, and improvement of the weldability is expected as compared with the conventional example containing no Hf. . In the figure, ● indicates base alloy composition A,
▲ corresponds to the base alloy composition B.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

Further, based on the alloys of the above-mentioned composition A and composition B, Hf was added thereto and vacuum-melted, and the obtained molten metal was atomized in an oxygen-free atmosphere to produce a Ni-based alloy powder, and HIP was used. The sintered material (O ₂ content: 7
The elongation at room temperature and high temperature was examined by a tensile test using 7,72 ppm, Hf content: 0.5 , 0.6 %). The result is shown in FIG. For comparison, a sample was manufactured under the same conditions except that Hf was not dissolved in the atmosphere, and the same test was performed. The results are also shown in FIG. In the figure, ○ and △ are vacuum melting materials, ● and ▲ are atmospheric melting materials, ○ and ● correspond to the base alloy composition A, and △ and ▲ correspond to the base alloy composition B. From the figure, low O according to the embodiment
₂ content, Hf content (○, △) is the conventional example (●
・ It is recognized that the elongation is remarkably improved compared to ▲).

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

Next, as shown in FIG. 6, a composite valve rod for marine low-speed diesel engine (dimension surface 450 mm in diameter) was manufactured, and after heat treatment, weldability was tested. The composite valve rod is manufactured by forging the valve rod main body 5 with austenitic heat-resistant steel (SNCrW) and performing Ni plating with a thickness of 50 μm along the lining layer joining surface of the main body 5, that is, from the lower surface of the umbrella portion 6 to the peripheral upper surface. A layer (not shown) is formed, a capsule is attached so as to cover the joint surface, and a mnemonic 8 having an O ₂ content of 72 ppm and a Hf content of 0.5% is provided between the joint surface and the capsule.
After filling 0A alloy powder and degassing the gas in the powder filling space through the degassing tube provided in the capsule, 1000 ° C., 100
HIP treatment was performed at 0 kgf / cm ² , and the powder was sintered to form the lining layer 7 and joined. The O ₂ and Hf contents of the lining layer 6 after sintering were substantially the same as those of the powder.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroshi Takigawa 2-3-1, Niihama, Arai-cho, Takasago, Hyogo Prefecture Takasago Works, Kobe Steel, Ltd. (72) Hideaki Ide, Niihama, Arai-cho, Takasago, Hyogo Prefecture No. 3-1 Takasago Works, Kobe Steel, Ltd. (72) Masayoshi Izaki Inventor, Masayoshi Izaki 2-33-1, Niihama, Arai-cho, Takasago-shi, Hyogo (72) Takasago Works, Kobe Steel, Ltd. (72) Koichi Umeda, Takasago-shi, Hyogo Prefecture 2-3-1, Niihama, Arai-cho Takasago Works, Kobe Steel, Ltd.

Claims (4)

[Claims] [Claim 1] A Ti-Al-Cr-Ni-based heat-resistant corrosion resistant alloy powder was pressureless sintered by hot isostatic pressing, a Ni-based powder sintered alloy was dense integrated, O ₂ content Is 85 pp
A Ni-based powder sintered alloy having excellent weldability, which is characterized by being m or less. 2. A Ni-based powder sintered alloy in which a Ti—Al—Cr—Ni heat-resistant and corrosion-resistant alloy powder is pressure-sintered by hot isostatic pressing to form a densely integrated Ni-based powder alloy having a Hf content. 0.2 ~
Ni with excellent weldability characterized by being 1.5 wt%
Base powder sintered alloy. 3. The Ni-based powder sintered alloy according to claim 1, which has an Hf content of 0.2 to 1.5 wt%. 4. A Ti is formed by hot isostatic pressing from the lower surface of the umbrella portion of the valve stem body made of a heat-resistant alloy to the upper surface of the peripheral edge portion.
A composite valve rod in which a -Al-Cr-Ni heat-resistant and corrosion-resistant alloy powder is pressure-sintered to form a lining layer and the lining layer is joined, wherein the lining layer comprises claim 1, 2 or 3. The lining layer is made of Ni-based powder sintered alloy.
A composite valve rod characterized by being joined via a plating layer.