JPH0390535A - Wear-resistnat zr alloy member and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture the Zr alloy member excellent in wear resistance and erosion resistance by forming the structure at least of a surface layer part in a Zr alloy member from the one of which ZrC is dispersed into a matrix. CONSTITUTION:Zr or Zr alloy is mixed with carbon and/or metallic carbide or furthermore with hard grains, which is melted to disperse ZrC or hard grains except ZrC as well into a matrix. Or, the surface of a Zr or Zr alloy member is clad by welding with a cladding material of carbon and/or metallic carbide or furthermore contg. hard grains to form the structure of the surface layer part in the member from the one of which ZrC or furthermore hard grains except ZrC are dispersed into the matrix. Moreover, as the metallic carbide, Cr3C2, W2C, VC, Mo2C or the like are used, and as the hard grains, Al2O3, Cr2O3, ZrO2 or the like having about <=150mu grain size are used. In this way, the Zr alloy member useful as the structural material for various chemical plants, nuclear power plants, etc., can be obtd.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a member made of zirconium or zirconium alloy (hereinafter collectively referred to as rZr alloy) that has excellent corrosion resistance, and which also has excellent wear resistance and erosion resistance. It also relates to excellent members and methods of manufacturing them.

The main uses of the Zr alloy members of the present invention include structural members for chemical plants, nuclear power plants, etc., and various equipment for oil wells.

(Conventional technology) Materials for various chemical plants, oil well related equipment, nuclear power plants, etc. are often required to have excellent corrosion resistance.
Even stainless steel such as SO5304 may not be able to meet the requirements. For example, for an acetic acid manufacturing plant, T
Even the i alloy lacks corrosion and acid resistance, and a highly corrosion resistant 2'' alloy is sometimes used.

Corrosion resistance requirements are also becoming stricter for oil well equipment.
Although Zr alloy is being considered as a substitute material for stainless steel and the like, the problem is that Zr alloy has poor wear resistance and erosion resistance.

Structural materials for nuclear power plants are required to have excellent corrosion resistance and erosion resistance in high-temperature, high-pressure water, and valves and valve seats must have wear resistance in addition to the above characteristics. Conventionally, SO3304 and CO-based alloy Stellite Nα6 (trade name) have been used as materials for the internal structure of nuclear reactors, and have exhibited excellent corrosion resistance and wear resistance. In addition, Stellite NIL6 is used for the valves and valve seats by overlaying S[l5304 with Stellite NIL6.

In particular, the following problems are pointed out regarding the structural materials inside the nuclear reactor as described above.

In order to achieve sophistication of light water reactor technology, light water reactor equipment,
In addition to extending the life of parts and improving reliability, efforts must be made to reduce radiation exposure for inspection workers. In order to reduce radiation exposure, "Co," which is the structural material of the reactor system, SO3304 and Stellite NQ, 6, corrodes in the cooling water, is eluted by erogidine, and is activated in the reactor core.
Go (activated magnetic field generation from Ni), S4Mn, 59
Various radioactive elements such as Fe, especially 60Co which has a long half-life
It is considered an important issue to suppress the elution of radioactive corrosion products as well as the accumulation of these radioactive corrosion products on piping. A similar problem is the wear and elution of Co in stellite used for friction parts such as valves and valve seats.

Against this background, in order to reduce radioactive products, C.

There is a strong demand for materials that do not contain SO3304 and have excellent corrosion resistance and wear resistance as nuclear reactor core components.
The current situation is that there is no practical material that is superior to Stellite Hiro 6 in all properties such as corrosion resistance and abrasion resistance in high-temperature, high-pressure water.

The environments in which they are used in various chemical plants, oil well-related equipment, etc. are becoming increasingly harsh, and conventional corrosion-resistant and wear-resistant materials such as Ti alloys and stellite are sometimes considered to lack performance.For example, 5IJS3 used in food manufacturing plants
For 04, it is possible to build up Stellite in areas where wear resistance is required, but depending on the corrosive environment, CO leaching
The toxicity of these substances is a problem, and they may not be usable. In the field of oil wells, there has been an increase in the development of highly corrosive oil fields, and for this purpose materials for oil well pipes, such as drill pipes, are required to have not only high corrosion resistance but also wear and erosion resistance. It has become.

Zr alloys have excellent corrosion resistance, especially hydrogen sulfide corrosion resistance, and do not have the problem of Cote release, so they are expected to be corrosion-resistant materials in the various industrial fields mentioned above, and are already in practical use in some areas. However, Zr alloy has poor wear resistance and erosion resistance. Therefore, it cannot be applied as is to, for example, valves, valve seats, impeller turbine blades, nuclear reactor internal materials, etc. of various chemical plants.

(Problems to be Solved by the Invention) The present invention has been made with the object of making use of the excellent corrosion resistance of Zr alloy to provide various members made of the alloy with high wear resistance and erosion resistance.

<Means for Solving Problem 81) The present inventors obtained the following findings in the course of research aimed at improving the wear resistance and erosion resistance of Zr alloys. That is, (1) If stable zirconium carbide (ZrC) is uniformly dispersed in a Zr alloy to form a Zr-based coarse particle dispersed composite alloy, its wear resistance and erosion resistance will be significantly improved.

(2) When various carbides are mixed and dissolved in Zr alloy, ZrC, which has a low free energy of formation, crystallizes finely and uniformly during solidification. Since ZrC is a crystallized reaction product, it is extremely thermally stable and heat resistant.

■ ZrC can be dispersed in Zr alloy by mixing and dissolving only carbon (C), but carbides containing elements that convert Zr into β phase, i.e. Cr5Cis LC, VCl
When one or more types of MolC are mixed and dissolved to form a β phase matrix, wear resistance and erosion resistance are further improved.

■In addition to ZrC, other hard particles are dispersed to improve wear resistance.
It is also possible to further improve erosion resistance.

■The above measures may be applied to the entire part, but
The coating may be applied only to the surface layer of the member requiring erosion resistance, for example, using a build-up technique.

The gist of the present invention based on the above knowledge is the following (1) to (4).

(1) A wear-resistant Zr alloy member, characterized in that at least the surface layer thereof has a structure in which ZrC is dispersed in the base material.

(A wear-resistant Z member made of 21 Zr or Zr alloy, characterized in that at least the surface layer thereof has a structure in which ZrC and hard particles other than ZrC are dispersed in the base material.)
r Alloy members.

(3) The method of (1) above, characterized in that carbon or/and metal carbide, or further hard particles are mixed and dissolved in Zr or Zr alloy, and ZrC or further hard particles other than ZrC are dispersed in the base material. (2) A method for manufacturing a wear-resistant Zr alloy member.

(4) Overlaying the surface of a member made of Zr or Zr alloy using a build-up material containing carbon or/and metal carbide, or further hard particles, and applying Zr to the surface layer of the member as a base material.
The method for manufacturing a wear-resistant Zr alloy member according to (]) or (2) above, characterized in that the material is made of am, in which hard particles other than ZrC or further hard particles other than ZrC are dispersed.

In the present invention, Zr alloy refers to industrially pure zirconium and Crs Nbx Sn, Ta, MO%
W% V, Ti, Aj! zirconium base metal containing one or more alloying elements, such as Zircaloy 2, Zircaloy 4, etc., and all α-based, α+β-based, and β-based zirconium alloys.

These Zr alloys have superior corrosion resistance (for example, in a high-temperature, high-pressure water environment) and acid and hydrogen sulfide corrosion resistance compared to stainless steels such as SO3304 and Co-based alloys such as Stellite N116. Moreover, C.

Because it does not contain any of

The "member J" of the present invention refers to all equipment parts, pipes, plates, and other intermediate materials.
The surface layer portion, which should have erosion resistance, is characterized by a structure in which ZrC is dispersed in the above-mentioned Zr alloy matrix.

It is necessary to finely and uniformly disperse ZrC in the Zr alloy matrix in order to improve wear resistance and erosion resistance. As one of the methods, Zr alloy and carbon (C)
or/and metal carbide (CrsC□, WtC, VC
, Mo1C, TiC5ZrC, NbC, etc.).

When only carbon is mixed and dissolved, this carbon crystallizes as ZrC in the Zr alloy. Carbide, e.g. CraCz
When mixed and dissolved, Cr5f, +2 Zr -2ZrC+3 Cr -(
In the reaction a), ZrC is produced, and the separated Cr is dissolved in the matrix. If the above-mentioned carbides, which have a higher free energy of formation than ZrC, are used, all of them will react as shown in equation (a), and ZrC, which is an extremely stable carbide, will crystallize during solidification, and the remaining Cr, W, V, Mo5Ti, etc. Solid solution in Zr matrix.

The matrix in which ZrC is dispersed is α phase, α + β phase, β
It may be either phase. However, the high toughness of BCC (
If it is a β phase with a body-centered cubic structure, the properties will be further improved.

Therefore, the basic alloy constituting the member is α phase, or α + β
When the phase is a Zr alloy, for example, if Cr, C, LClVC, MozC are used as the carbides to be mixed and dissolved, Cr, W, V, separated as in formula (a) above,
The β phase is generated or increased in the matrix by the action of No (all of these are β phase stabilizing elements).

Since ZrC is a crystallized reaction product, it is extremely thermally stable. Therefore, the problem peculiar to general particle-dispersed alloys in which the properties change due to the reaction between the dispersed particles and the matrix, resulting in solid solution and diffusion, does not occur. Moreover, Z
Since rC has a high hardness (Hv2800), the hardness of the composite alloy becomes extremely hard, and wear resistance and erosion resistance are significantly improved.

The reason for dispersing ZrC in the matrix is that ZrC itself does not adhere to the mating material, has a sliding effect, and increases the overall hardness due to the compound law, improving wear resistance and erosion resistance. In this case, the matrix needs to have a carbide retention function and is desirably highly tough. In this sense, it is preferable that the matrix has a structure with as much β phase as possible, or a complete β phase.

Composite agents refer to the strength of composite materials in which hard substances are dispersed (
This is the law that σ (hardness) is expressed as σ−σfVf+σm V m. Here, σ,: Strength of the hard substance ■f: Volume fraction of the hard substance σ,: Matrix strength ■,: Matrix volume fraction.

In order to increase the hardness and, on the other hand, maintain good workability, the amount of ZrC in the Zr alloy matrix should be between 5 and 5.
A range of 1% by weight is desirable; less than 5% by weight will result in poor wear resistance;
The effect of improving erosion resistance is small, and if it exceeds 50% by weight, ductility becomes poor and processing becomes difficult.

The above effects can be achieved by using a suitable particle size (150 μm) in addition to crystallized ZrC.
The improvement is further improved when hard particles of - or less are desirable) are dispersed. Hard particles include ^1803, Cr*(h,
Metal oxides such as Zr01, Sing, Ti1t, TaO, metal carbides such as HfC, SiC, TaC, BN, T
ie, Cr5N.

Metal nitrides such as NbN, ZrNSMotN, HfN, TaN, TiBt, VBz, CrBx, ZrBz
Examples include hard intermetallic compounds such as NiTi, NiTi, and the like. As a method for dispersing such hard particles in a Zr alloy matrix, there is a method in which the Zr alloy is melted at a temperature higher than the melting temperature of the Zr alloy and lower than the melting temperature of the hard particles, and then solidified.

Note that there is no problem even if some of the metal carbides such as Cr and Cz mentioned above are dispersed as they are in the matrix without being decomposed.

What has been described so far is a method of making the entire member wear-resistant and erosion-resistant. In addition to this method, there is a method in which only the necessary portion (predetermined surface layer portion) of the member is provided with the above-mentioned structure. That is, a structure in which ZrC or ZrC and other hard particles are dispersed is formed on the surface of a Zr alloy member (base material) by a build-up method. In this case, for example, a mixed powder of Zr and metal carbide such as Cr5Cz, or one or more of the above-mentioned hard particles added thereto, is used as a build-up material, and the surface of the base material is coated with laser build-up or PTA. The surface layer is made of a ZrC-dispersed Zr alloy using a method such as overlaying to improve the wear resistance and erosion resistance of the surface.

Furthermore, by using the above melting method and processing methods such as forging and rolling, ZrC1 or Z in which ZrC and other hard particles are dispersed can be produced.
It is also possible to produce an r-alloy plate and weld it to a predetermined surface of a Zr-alloy member that requires wear resistance and erosion resistance. This welding is difficult due to the TrGi welding method, etc.
Can be implemented.

The ingot material of ZrC1 or Zr alloy in which ZrC and other hard particles are dispersed according to the present invention can be easily hot-rolled by heating to around 1000°C. Its wear resistance is equal to or higher than that of stellite due to the action of high hardness ZrC1 or even harder particles, and it also has excellent corrosion resistance. As mentioned above, it is more desirable to have a structure with a high toughness and a large amount of β phase.

[Example 1] First, an example will be shown with nuclear power plant members in mind.

A Zr alloy having the components shown in Table 1 was melted by an Ar arc melting method to obtain an ingot having a thickness of 30I1ml x width of 501w11 x length of 100+IIm. The alloy raw materials used were sponge Zr, C powder, and -tc, TiC,C.
rzC2, MozC, TiN.

It is powder of ZrC5A1102, TiB, and NbC.

Next, these ingots were heated to 1050°C and then hot rolled in 5 passes to a 12mm thick plate, and the occurrence of defects such as cracks due to hot rolling was investigated, and the structure was determined by XvA analysis. I did it.

These results are also listed in Table 1.

The hardness (Vickers hardness) at room temperature of the obtained rolled plate (10+u+thickness) was measured, and the diameter was 101IIIl.
x length 40 old sliding wear test piece (pin 1 in Figure 1) and thickness 10++n x width l0III x length 15 open erosion test piece, length 25m + s x width 10ll
A high temperature corrosion resistance test piece with a thickness of 3+wm and an environmental resistance test piece with a length of 25 mm x width of 10111111 x thickness of 1+m were taken and subjected to the respective tests.

As comparative materials, thin plates and rods of SO5304 with a thickness of 4III1 and cast plates and rods of Stellai) N116 with a thickness of 4III11 were used, processed into various test specimen sizes, and subjected to tests.

The "wear test" was conducted using the bin-on-day star method shown in Figure 1, and the test conditions were: load: 2 kg, sliding speed with heavy mating material (disc 2): 62.8 m/s
In sliding distance: 2.5 x 10'm Mating material (disk 2): SOS 304, HT
Lubrication of the 60 steel friction surface: None, and the wear resistance was evaluated based on the amount of weight loss of the bottle at this time.

The water jet method shown in Fig. 2 was used for the "Erosion Test", and water was sprayed onto the surface of the test piece 3, which had been polished to a mirror surface by puff polishing in advance.Nozzle diameter: 1.2+mφ Water flow rate: 310a/see Test temperature : Room temperature nozzle - test piece open circuit 1'tl : 65m5 Injection angle:
After spraying high-speed water under conditions of 90° spraying time: 600 seconds, the depth of the traces produced was measured and the erosion resistance was evaluated.

"High-temperature corrosion resistance test" is conducted in pure water using an autoclave.
The test was carried out at 00°C for 200 hours, and the evaluation was made by measuring the corrosion weight increase in that case.

The "environmental resistance test method" was conducted under the following conditions assuming the environment inside a nuclear reactor (under γ-ray irradiation).

TwA dose rate: 1.5X10' rad/h pressure crab
70-80kgf/c+m” Concentration = 275-280℃ Water quality: 500ppmB +2ppmmL++ Hydrogen aeration 50% of Fe, Ni, Cr and Co under these conditions
The elution amount at 0 hr was investigated.

Table 2 shows the results of these tests. As shown in Table 1, all of the invention examples (Nal to 10) have a structure in which ZrC1 or other hard particles are dispersed, and there is no problem in hot workability. From Table 2, the Zr alloy composite material of the present invention has good sliding wear resistance and erosion resistance, surpassing the comparative example Stellite N116, and also has good corrosion resistance in an environment equivalent to the inside of a nuclear reactor. Excellent, and because it is a Zr group, there is no elution of Co. That is, it is clear that it is extremely useful as a structural material inside a nuclear reactor. As shown in Table 1, the matrix of Nos. 1 to 4, 8, and 9 is a β single phase, and their sliding wear it (Table 2) is higher than that of NcL5 to 7, whose matrix is an α phase. few.

[Example 2] Next, an example will be shown in which a member of the present invention was manufactured by a build-up method.

Pure zirconium as base material, diameter 100+wm, length 40
++n disc was used, and in order to make ZrC 13.6% by weight, PTA was applied onto the disc under the conditions shown in Table 3 using a mixture of Zr powder and 13% by weight Cr3C1 powder as overlay material.
Filled with meat. Hardening depth (depth from base metal surface) is 2.8m-
However, no defects were observed in the build-up area, which was in good condition. A wear test piece with a diameter of 10 mm and a length of 4 (lu + (Fig. 1), it showed wear resistance equivalent to floor 1 in Table 1.Erosion resistance and corrosion resistance were also
It was equivalent to N11l in the table.

In addition, it was observed that ZrC was uniformly dispersed and crystallized in the built-up portion.

[Example 3] An example in which the members of the present invention were studied for use in chemical plants will be shown.

A test piece with a thickness of 8 mm x width of 20 mm x length of 20 m + * was cut out from the hot rolled plate of Mal~3 of Example 1, and an acid resistance test was conducted.

The experimental conditions were 50% sulfuric acid and 80°C, and the amount of corrosion was measured. As comparison materials, SOS 304 and Zr alloys (Same 11 and 13 in Table 1) were used. The test results are shown in Table 4.0
The product of the present invention is extremely superior to SUS 304 and Z
It has the same level of acid resistance as r-alloy. Furthermore, as shown in Table 2, it has excellent sliding wear resistance and erosion resistance with respect to HT60 steel, so it can be said to be extremely useful as a material for chemical plants.

[Example 4] An example in which the member of the present invention was investigated as a material for oil well equipment will be shown.

From the hot rolled plates of Sou 1 to 3 in Table 1, 50 pieces in length x 5 pieces in width
Table 5 shows the conditions under which hydrogen sulfide (Has) resistance was evaluated by cutting out a plate-shaped test piece of 011II x 10 mm thickness and using it as a C-ring test piece of STM 038-73 shown in FIG. As a comparative material, N11ll 5 in Table 1
US304 and pure zirconium were cut into the same shape and tested. The test results are shown in Table 6. SCC (stress corrosion cracking) did not occur in any of N11l~3, but SU
SCC occurred in S304. From this result, it is clear that the member of the present invention exceeds SUS 304 in hydrogen sulfide resistance. In addition, as mentioned above, it has excellent sliding wear resistance and erosion resistance, so it is extremely useful as a material for oil well equipment.

(Hereafter, margin) No. 3 table No. table No. table Load stress 0.80xσ. ,t 0kg17m”).

S is sulfur.

(Hereinafter, blank space) (Effects of the invention) According to the present invention, the original corrosion resistance of Zr alloy is not impaired,
It is possible to provide members manufactured with the alloy with excellent wear resistance and erosion resistance.

The member of the present invention has excellent acid resistance, hydrogen sulfide resistance, wear resistance, and erosion resistance, and exhibits high corrosion resistance especially as a nuclear reactor core structural material, and does not cause problems caused by radioactive elements like CO-based alloys. There's no fear.

The members of the present invention may be used as plate materials, pipe materials, etc. by taking advantage of their excellent hot workability, and may also be used by forming a wear-resistant build-up layer on the surface of ordinary Z alloy members. The range of application of the members of the present invention is extremely wide, including various chemical plants, oil well related equipment, nuclear power plants, etc.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram illustrating the sliding wear test method. FIG. 2 is a conceptual diagram explaining the erosion test method. FIG. 3 is an explanatory diagram of a C-ring test piece for investigating hydrogen sulfide resistance based on ASTM G38-73.

Claims (4)

[Claims] (1) A wear-resistant Zr alloy member, characterized in that at least the surface layer thereof has a structure in which ZrC is dispersed in the base material. (2) A wear-resistant Z member made of Zr or Zr alloy, characterized in that at least the surface layer thereof has a structure in which ZrC and hard particles other than ZrC are dispersed in the base material.
r Alloy members. (3) Zr or Zr alloy is mixed and dissolved with carbon or/and metal carbide, or even hard particles, and Zr is added to the base material.
Wear resistance Z according to claim (1) or (2), characterized in that hard particles other than rC or ZrC are further dispersed.
A method for manufacturing an r-alloy member. (4) Overlaying the surface of a Zr or Zr alloy member using a build-up material containing carbon and/or metal carbide, or further hard particles, and using the surface layer of the member as a base material to coat ZrC,
The method for manufacturing a wear-resistant Zr alloy member according to claim 1 or 2, further comprising a structure in which hard particles other than ZrC are dispersed.