JPH0494890A - Erosion resistant coating material and method for forming this - Google Patents

Abstract

PURPOSE:To restrain cavitation and erosion and to prevent erosion in apparatus by forming a build-up layer of solidified structure construction crystallizing complex carbide of Cr carbide or chromium as the essential substance in a net-work state in the matrix of alloy on the surface. CONSTITUTION:The build-up layer having the solidified structure construction precipitating and crystallizing the complex carbide of Cr carbide or chromium as the essential substance as the net-work in the welded build-up layer on the surface of the metal basis composed of alloy containing at least one kind of Fe and Ni as the essential component and 15-30wt.% Cr, is formed on the surface of apparatus member. For this purpose, wear caused by cavitation, soil and sand, etc., and erosion caused by water drop are restrained and therefore, erosion in the apparatus is prevented and reduction of driving efficiency can be decreased and large effect to improvement of the service life, is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an erosion-resistant coating material, and in particular to powder,
This invention relates to an erosion-resistant coating material that prevents damage by forming a weld build-up layer by powder melting on the surface of equipment components that are damaged by collisions, impacts, and cutting actions of earth and sand water, oil, water droplets, steam, and slurry cavitation.

[Conventional technology]

Equipment that handles fluids, gases, solids, and mixed flows of these materials is subject to erosion damage due to collisions, blows, cutting, and scratching caused by the flow of these media. The damage occurs both locally and over the entire area in contact with the medium. The following is a classification of media that handle devices and parts that are subject to such erosion damage.

Liquids: Steam turbine blades, airplane wings, oil combustion equipment, heat exchanger tubes, bent pipes, etc.Gas-liquids: Water turbines, valves, pumps, ship wings,
Gas-solids such as Venturi pipes: Air transport pipes for powder and granules, various dust collectors, aircraft turbine blades, pulverized coal and fluidized bed boilers, coal gasifiers, etc. Liquid-solids: Slurry transport pipes, sand pumps, slurry pumps, Solid equipment, equipment, etc. in the coal conversion process: Zandblasting nozzles, shotblasting impellers and liners, hoppers, blow tank discharge pipes, bends, etc. of air conveyance equipment, etc. Measures to prevent erosion of these equipment and parts include:
Methods have been taken to change the structure and apply erosion-resistant abrasive materials. Looking at materials in particular, the most common material technology for preventing erosion damage is improving the hardness of materials. Therefore, cemented carbide, ceramics, etc. have come to be used. However, if such high hardness materials are not used, there is little possibility that they can be supplied as structural members on their own (G). Therefore, there is a strong tendency for it to be applied as a method for bonding with structural base materials and preventing erosion.

The cemented carbide is joined by brazing with the base material and by overlay welding the cemented carbide itself onto the base material.

Furthermore, since it is currently difficult to supply ceramics as a large, integrated product, we are trying to apply the method of laminating small pieces onto a base material, and if it is a small diameter pipe, it can be applied as a laminated pipe inside and outside of a steel pipe.

However, when considering application to large structures, cemented carbide has problems with workability, particularly cracking due to overlay welding, and furthermore, application of ceramics is difficult in terms of construction. Particularly problematic is the application to rotating equipment, where such alloys and ceramic structures are extremely difficult to manufacture.

Examples of rotating bodies that are particularly prone to erosion damage include water turbine runners and buckets as hydraulic equipment, steam turbine blades, ship propellers,
Examples include slurry and Zand pump impellers.

In particular, parts that come into contact with flowing water such as water turbine runners, guide vanes, stevens, buckets, and nozzles for hydroelectric power generation equipment are susceptible to damage due to sand and sand contained in the river water, as well as cavities due to the shape of the parts and flow velocity. cavitation damage due to impact.

In order to prevent this cavitation damage, metal overlay welding materials have been developed to suppress cavitation damage by overlaying stainless steel materials with excellent resistance to cavitation and erosion on the surface of the base material in contact with flowing water. It has been. The compositions of these welding materials are disclosed in JP-A-57-152447, JP-A-57-156894, and JP-A-57199.
It was disclosed in Japanese Patent No. 593, and stainless steel materials have been used. Metal materials that can suppress damage caused by cavitation include those with high strength and hardness (Vickers hardness of 2350 to 450), or austenitic materials that are expected to work harden the surface layer of flowing water using impact pressure. It is a welding material.

However, with regard to soil abrasion, damage to water turbine components has become a problem not only in Japan but also in countries such as the People's Republic of China and India, which utilize river water containing large amounts of soil and sand. This is earth and sand that is harder than the components of the water turbine (the main component is 5
This is because it is eroded by the cutting action of Al 102 and Al 203).

Therefore, even cavitation-resistant materials do not necessarily have good earth and sand abrasion resistance. This is because the damage mechanisms are different.

on the other hand,! Erosion of air turbines is particularly problematic in the high-pressure first stage nozzle, reheat first stage nozzle, rotor blades, and main steam stop valve. This corrosion is caused by oxidized scale (Fe203, Fe30) discharged from boiler superheaters and reheaters.
This is because 4) is affected. Therefore, in order to prevent these problems, surface treatment materials such as boron treatment and Cr pack treatment are considered to be effective. Furthermore, the low-pressure final stage rotor blades are subject to erosion by water droplets in the wet steam. To prevent these problems, quenching and hardening the rear leading edge of the rotor blade, where water droplets collide, and pasting or overlaying using Co-based materials, silver brazing, etc., have been taken. However, efforts are being made to reduce CO in nuclear power turbines, and the development of new materials is desired.

On the other hand, there are various construction methods for preventing erosion caused by collisions of cavities and water droplets, as well as abrasion caused by cutting action caused by earth, sand, scale, or powder. However, especially when applied to rotating objects, the welding overlay method is mainly used because bonding strength with the base material is required. This method includes shielded arc welding, 'l' I G
Welding, powder plasma welding, electroslag welding, etc. each have their own characteristics.

In these welding processes, composite overlay welding materials have recently been researched and developed. As one of the materials for coated arc welding, a technique for forming a build-up layer on the surface of a base material using a mixed powder with Co-based super super heat-resistant alloy powder ceramic powder was disclosed in Japanese Patent Application Laid-Open No. 6.
1-134193. Furthermore, research on plasma arc build-up welding materials using such powders has been published.

[Problem to be solved by the invention]

Conventional metal welding materials are susceptible to damage due to cavitation, erosion, and abrasion caused by sand and sand, as described in the example of water turbine materials in the previous section, due to the damage
Erosion cannot necessarily be prevented using the same material. That is, the former is a phenomenon in which erosion occurs due to impact pressure when a cavity generated in high-speed water collides with the material surface and collapses, and the latter is a phenomenon in which erosion occurs mainly due to the cutting action of earth and sand. Therefore, simply increasing the hardness is not effective. An example of this is ceramics.

Since these have high hardness, they have very good earth and sand abrasion resistance, but their cavitation resistance is not so good.

In other words, it is strong against cutting action, but weak against impact action. Therefore, considering wear caused by sand and powder, especially damage to materials caused by liquids and solids, we believe that materials that have both cavitation resistance and wear resistance due to sand and powder are promising. Therefore, even if cemented carbide, ceramics, etc. are applied to the surface of a structural member, good results cannot necessarily be obtained and there is a problem in terms of reliability. Therefore,
It became important to develop materials with the properties of the partner.

Therefore, as a result of considering these construction methods, we found that the overlay layer using a coated arc welding rod has a large dilution with the base material, so it is necessary to increase the amount of overlay, and that materials with high hardness cannot be manufactured. It was found that the weld cracking susceptibility was increased. However, it has become clear that plasma arc welding using powder requires less dilution with the base material, so a thin amount of overlay is required. Therefore, when using this welding method, in order to provide both cavitation resistance and earth and sand wear resistance, it is necessary not only to improve the hardness but also to form precipitates on the network in the matrix. It turned out that it was effective to let them out.

The object of the present invention is, in particular, to prevent cavitation damage due to cavity impact, collapse, and scratching and cutting effects by solids on equipment that is used in a mixed flow of liquids, solids, and gases and that comes into contact with this mixed fluid. It is an object of the present invention to provide a covering material provided with an erosion-resistant build-up layer that simultaneously suppresses wear and damage due to wear and tear and is easy to construct, and a method for forming the same.

[Means to solve the problem]

In order to achieve the above object, in the present invention, at least one of Fe and N1 is the main component, and 4Cr is 15 to 3% by weight.
In the coating material, which is a weld build-up layer on the surface of a metal base made of an alloy containing 0%, the matrix of the alloy has a metal structure in which chromium carbide or composite carbide mainly composed of chromium is crystallized in a network shape. Vickers hardness (Hv) 50
0 or less, and in the present invention, the surface of a metal substrate made of an alloy mainly composed of at least one of Fe and Ni and containing 15 to 30% by weight of 4Cr. The coating material, which is a weld overlay layer, has a metal structure in which chromium carbide or a composite carbide mainly composed of chromium is crystallized in a network shape in the IJ hook of the alloy, and contains 3 to 10% by weight of silicon. This is an erosion-resistant coating material characterized by containing:

In order to achieve the other objectives mentioned above, in the present invention, wt%
C: 0.15% or less, sl: 0.2-1.0%, Mn
: 15% or less, Ni: 50% or less 4Cr: 15-30%
and the balance is Fe, and 5 to 15% by weight of Si.
This is an erosion-resistant welding material made of C powder.

Furthermore, in the present invention, as the method for forming the coating material, the weld build-up layer has a powder particle size (S) of the metal carbide and a powder particle size (M) of the austenitic stainless steel or nickel-based alloy of 10 A mixed powder consisting of a particle size ratio of ~200 μm and a particle size ratio S/M of 1 or less was laminated on the surface of the equipment member by plasma arc welding, and the thickness was at least 5 mm or less. It is something.

The weld build-up layer is a layer obtained by overlay welding by melting a mixed powder of austenitic stainless steel or nickel-based alloy powder and metal carbide powder using a plasma arc and supplying it to the part to be welded. The crystallized carbide is characterized in that it is not composed of the remaining mixed metal carbide, but is produced as a new phase due to alloying elements that constitute the austenitic stainless steel or nickel-based alloy. This welding method is characterized by forming an overlay weld layer of a desired thickness while creating a pool of molten metal in the welded part.

Furthermore, metal carbides such as SiC, FE! 3
C, Ni3C4C02C, or 84C, and is preferably contained in the weld build-up layer in an amount of 1 to 50% by volume.

In particular, carbide formation tendency (Nb>'ri>v>w>Mo
>Cr>Mn>Re>Ni>Co>Si) and contains at least Sl, which dissociates from carbon and mixes into the matrix to promote the formation of carbides of other elements, is preferred.

The content of carbides crystallized and precipitated is 1 to 5 in terms of area ratio.
0% is preferred. Particularly in areas that receive a strong impact from running water and suffer only cavitation damage, the overlay weld layer should have a high toughness, preferably 1 to 20%. Also,
In areas where wear is dominated by solids contained in the fluid medium, the ratio is preferably 20 to 50%. It should be noted that 15 to 30% is preferable for areas that are subject to combined cavitation damage and abrasion caused by solid matter.

The hardness of the overlay layer is 30 in terms of Vickers hardness (11ν).
0 to 700, particularly preferably 500 or less in Hv. The relationship between the amount of silicon carbide or silicon-containing carbides added and the area ratio of precipitated and crystallized carbides contained in the overlay weld layer is 20% when the amount of crystallized carbides is 10% by volume relative to silicon carbide, and 25%. When the capacity is %, it is 40%, and when the capacity is 40%, it is 60%.

The composite powder used to form this weld overlay layer has a powder particle size (S) of silicon carbide or silicon-containing carbide and a powder particle size (M) of austenitic stainless steel or nickel-based alloy of 10 to 200 μm, respectively. It is preferable that the grain size ratio S/M is 1 or less and that silicon carbide or a carbide containing silicon is contained in the weld overlay layer in an amount of 1 to 50% by volume.

Further, as the austenitic stainless steel or nickel-based alloy, Al5I 304, 316°31
08, 683, 690, etc. can be used. That is, in the present invention, in order to precipitate and crystallize chromium carbide or a composite carbide mainly composed of chromium in the overlay weld layer, Cr by weight is
: Based on an alloy containing 15-30%. Preferably 4C': 0.15% or less, Si: 0.2 to 1% by weight.
0%, Mn: 15% or less, Ni: 50% or less,
Furthermore, Mo: 5% or less, N: 0.3% or less 4Co
: 20% or less, Nb: 5% or less, Ti: 5% or less, A1
It is preferable that the composition contains at least one of: 5% or less, B: 0.01% or less, and W: 5% or less, with the balance being Fe and accompanying inevitable impurities.

On the other hand, the present invention decomposes silicon and carbon by melting austenitic stainless steel or nickel-based alloy and silicon carbide or carbide powder containing silicon, and by adding it to the alloy, silicon becomes more carbide than the carbide. It precipitates and crystallizes chromium carbide and carbide mainly composed of chromium, which has a high standard energy of production reaction. Therefore, the same effect can be obtained even if an alloy powder with increased carbon and silicon content is melted alone and a weld overlay layer is formed on the base of the device. That is, it is an alloy with higher carbon and silicon content than the composition of the austenitic stainless steel or nickel-based alloy shown above. This content is wt% TeC: 0.3-2.0%, sl: 3-10%
is preferred. The particle size of this powder is preferably 10 to 200 μm.

In addition, the powder shape of any of the austenitic stainless steel, nickel-based alloy, alloy with increased carbon and silicon content, silicon carbide, or carbide containing silicon may be round,
Preferably, the powder has a square shape, a rounded square shape, or a mixture thereof, and a powder made by a gas atomization method with a low gas content is preferred. Preferably, the build-up weld layer is formed by plasma arc welding and has a thickness of 5 mm or less.

The erosion-resistant coating layer of the present invention can be applied to equipment members used in an atmosphere of powder, sand, water, oil, water droplets, steam, slurry, etc., and can be applied to equipment members that are used in an atmosphere containing powder, dirt, water, oil, water droplets, steam, slurry, etc. It suppresses damage.

[Effect]

Next, the action of the erosion-resistant coating layer of the present invention will be explained.

In the weld overlay layer having a metal structure in which chromium carbide or carbide mainly composed of chromium is precipitated or crystallized in at least a network shape, the density is lower than that of stainless steel or nickel-based alloy, and the precipitated or crystallized carbide is Silicon carbide, which has a higher standard energy for carbide generation reaction than other chromium carbides, is selected and mixed with austenitic stainless steel or nickel-based alloy powder to form a composite powder, which is then deposited onto the equipment base by plasma overlay welding. Form a welding layer,
As a result, a solidified structure in which chromium carbide or a composite carbide mainly composed of chromium is precipitated and crystallized in a network is formed.

For this purpose, the grain size of the austenitic stainless steel or nickel-based alloy and silicon carbide is preferably 10 to 200 μm. When these particle sizes are increased, undissolved metal powder and silicon carbide particles remain. However, the melting point of metal and silicon carbide powder is higher for silicon carbide, so when welding these composite powders, it is better to make the particle size of silicon carbide powder smaller than that of metal powder because it will be easier to melt by plasma arc. Therefore, it is preferable that 87M be 1 or less as described above.

Further, when using only austenitic stainless steel with increased carbon and silicon content or nickel-based alloy powder, the particle size is preferably 10 to 200 μm. In this case, as described above, since silicon carbide powder, which has a lower density than metal powder, is not mixed, welding workability is easy.

Furthermore, the powders used may be round, prismatic, rounded rectangular, or a mixture thereof, and may be produced by ordinary powder metallurgy techniques, but gas atomization to reduce the gas content in the particles may be used. Powder produced by this method is preferable. In addition, regarding the amount of overlay welding actually formed on the surface of the equipment component, the greater the amount of overlay welding, the better, but considering the ductility and toughness of these welds, and because almost no mixed layer is formed due to dilution with the base material. , 5 +r++n or less is sufficient, and cavitation resistance, abrasion resistance due to solid substances, etc., or combined damage resistance performance thereof can be exhibited.

In addition, when overlaying on the surfaces of equipment components that are subject to impact and cutting phenomena caused by powder, sand, water, water droplets, etc., we recommend using coated arc, TI
This can be done by a normal welding method such as G or MIG welding. However, it is relatively difficult to overlay weld composite powder of metal powder and silicon carbide powder or alloy powder with increased carbon and silicon content using these methods as in the present invention.

Therefore, plasma arc welding, in which powders can be mixed together or individually welded, can be effectively carried out.

According to the present invention, the erosion-resistant coating layer is applied to at least a portion of the surface of the equipment member that comes into contact with a fluid medium such as powder, sand water, water droplets, slurry, etc.
A composite powder of 1,5Mo-10Mn-0,2N austenitic stainless steel and a metal carbide ceramic of silicon carbide, which has a higher melting point and hardness than stainless steel, is used to form an overlay weld layer by plasma arc welding. This overlay weld layer has a structure in which composite carbides mainly composed of chromium are distributed in a mesh pattern in an austenitic stainless steel matrix, and this structure causes cavitation damage, wear damage due to solid objects, etc., and combined damage of these. can be suppressed and a highly reliable system can be constructed. In addition, 1, 2C-3,5Si-20C, which is obtained by adding carbon and silicon to the austenitic stainless steel
r-4Ni-6Co-1,5M.

The build-up weld layer with 10Mn-0,2N powder shows the same effect.

Next, one structure to which the erosion-resistant coating layer, which is a main component of the present invention, is applied will be described.

Figure 12-A shows a cross-sectional view of a Francis type water turbine;
12 is a perspective view of the runner section when viewed in the X direction in Figure 2-A.
- Shown in Figure B. The runner body, which is the moving blade of this water turbine, has a crown 1. A plurality of blades 3 are provided between the shroud 2,
Runner cone 4. Guide vane 5. It is composed of a steven 6, a runner liner 7, and a sheet liner 8, and flowing water containing earth and sand that has passed through the steven 6 flows from the guide vane 5 to the blades 3, gives rotational energy to the runner blades, and falls downward. 9 indicates a band.

The blade 3 is generally made of Ni13Cr cast steel 9 obtained by ordinary melting and casting. However, considering the damage caused by cavitation, conventionally welded austenitic stainless steel (stainless steel JISD308, D309) on the surface that comes in contact with running water.
Measures to prevent this have been taken by applying Mo, etc.). However, it has been found that these materials do not necessarily show good results in terms of soil abrasion. Therefore, we tested a high-hardness overlay weld metal material, but it did not necessarily provide satisfactory wear characteristics, and there were also limitations due to the relationship with the base material, such as cracks occurring in the overlay part. known. As a result of various studies, we focused on the fact that austenitic overlay welding materials have less weld cracking and are easier to work with, and have a cavitation resistance of JISD30.
8 and D309Mo. 20C
A layer was formed by producing a powder of r4Ni-6Co-1,5Mo-10Mn-0,2N austenitic stainless steel, and plasma welding a mixed powder obtained by mixing this powder with silicon carbide powder. It was revealed that this layer has a metal structure comprising an austenitic stainless steel matrix and carbides dispersed in this matrix, and has excellent cavitation resistance and earth and sand abrasion resistance.

The thickness of the build-up welding layer is 5 +++n+ or less, and although it may be multi-layered, it is sufficient to exhibit a sufficient effect with just one layer formed, and is preferably 1 to 3 mm. Incidentally, the powder used in the present invention can be obtained by a production method commonly used in powder metallurgy technology.

In addition, the aforementioned austenitic stainless steel powder is used as the base material of the mixed powder used in plasma overlay welding, which has good weldability and excellent cavitation resistance, and the erosion-resistant coating of the present invention This is because it can be supplied as a layer of metal powder.

Next, the reasons for limiting each component will be described. Note that the composition indicates weight %.

Regarding metallic powders, C is a strong austenite-forming element, contributing to stabilization of secondary stenite and strengthening of the matrix. When supplied as a composite powder with silicon carbide etc., the austenitic stainless steel and nickel-based alloy powder should not be reduced as much as possible using a special melting method, but within the range specified for ordinary Al51304 etc., that is, 0.03 to 0. A range of .15% is preferred. On the other hand, if the present invention is achieved by increasing the carbon and silicon content and using only metal powder, 0.2
4C is preferably in the range of 0.3 to 2.0% because it is ineffective if it is less than 5%, and if it is too much, a structure in which free C is released or the susceptibility to weld cracking increases.

Sl is added for deoxidation during melting of steel materials, and 0.
If it is less than 2%, this deoxidizing effect is insufficient. but,
When producing powder, the content may be at the level normally added, and the preferred range is 0.2 to 1.0%. On the other hand, in the case of using only a metal powder with an increased amount of carbon and silicon instead of a method using a composite powder such as silicon carbide, it becomes the main component to achieve this objective, as in 4C. For this purpose, it is ineffective within the range of providing a deoxidizing effect. When added in a large amount, it has the effect of improving other corrosion resistance, but when added in a larger amount, it causes embrittlement of solidification grain boundaries, etc., and the effect of forming chromium carbide, etc., which crystallizes and precipitates, does not change. A range of 10% is preferred.

Mn is usually added in an amount of 2% or less for deoxidizing and desulfurizing steel materials. This element contributes to an increase in the amount of N solid solution, and also
It stabilizes the austenite composition with i and CO and further softens the austenite base, but it also increases work hardenability and therefore significantly improves cavitation resistance. Furthermore, since increasing the amount of Mn added has the effect of increasing cutting resistance, wear resistance is imparted by solids and the like. In order to obtain this work hardenability, 7% or more is required, although it depends on the component balance with Ni etc. However, excessive addition of Mn impairs the flowability of the metal, leading to an increase in fumes during welding, and reducing welding workability. Therefore, in consideration of work hardening properties and wear resistance, the upper limit of the Mn content is set at 15% in the range according to the present invention.

Ni is an austenite-forming element, and together with Mn and Co, it stabilizes austenite and improves ductility and toughness. Therefore, it is an essential element for imparting ductility and toughness to the weld build-up layer.

However, austenitic stainless steel wire rods for welding contain 20 to 22.5% Ni, and nickel alloys containing Cr, which is necessary for the present invention as corrosion-resistant and heat-resistant alloy plates and high-temperature high-strength alloys, have a maximum of 40 to 45% Ni. Contains %. Therefore,
In the present invention, the maximum amount is set to 40% in consideration of the relationship with the Cr amount and the balance with 4C, Mn4Co, etc.

Cr is an element that must be included in austenitic stainless steel and nickel-based alloys. This element is an important element for improving corrosion resistance in water and at high temperatures, and for precipitating and crystallizing chromium carbide in the present invention. The amount is 1
When the content is less than 5%, the precipitates do not form a network, and although the cavitation resistance is improved, the wear resistance is inferior. If it exceeds 30%, the base becomes brittle even if it precipitates in a network shape, reducing cavitation resistance. The amount added to impart cavitation resistance and wear resistance of the present invention is preferably 15 to 30%.
In particular, 17 to 25% is suitable.

Co, together with Mn and Ni, moderately stabilizes austenite and particularly improves earth and sand abrasion resistance and cavitation/erosion resistance, so it is preferably contained in an amount of 12% or less. If it exceeds 10%, the base will be strengthened and the ductility and toughness will decrease.

In particular, CO in a range of 6 to 10% is suitable for earth and sand abrasion resistance, but it is limited to 10% in view of the relationship with cavitation resistance.

Mo not only strengthens the base but also improves corrosion resistance, and is effective in improving earth and sand abrasion resistance, cavitation resistance, and erosion resistance. However, if it exceeds 5%, the amount of δ ferrite produced increases and the toughness decreases.

Therefore, it is preferable for Mo to be in a range of 5% or less.

N works together with C to stabilize austenite, and is an essential element for austenite formation, especially in low C steels. It is also effective in improving soil abrasion resistance, etc.
If added in excess, it forms nitrides and impairs toughness.
It is preferable that N be 0.3% or less. More preferably, it is 0.05 to 0.2%.

Cu dissolves in the austenite base, strengthens the base, and improves soil abrasion resistance and cavidation resistance. However, if the addition amount is increased too much, cracks due to welding will increase, so the range is preferably 0.1 to 5%.

Nb, Ti, W, and V are grain refining and carbide forming elements, and when this type of carbide ceramics is not used,
It reacts with decomposed and melted C to form carbides and improve ductility and toughness. However, if added too much, weldability will deteriorate, so a range of 0.1 to 5% is preferable.

A1 is effective in improving corrosion resistance, especially oxidation resistance at high temperatures, but if added in too large a quantity, it will form oxides.
The content is preferably 3% or less since it impairs plasma weldability due to powder.

The remainder consists of Pe and accompanying impurities, including P, S, and other impurities. lvAs, Sb, etc., but these elements impair ductility and toughness as well as reduce weldability, so it is desirable to have as little as possible.

Regarding metal carbide ceramics, by mixing SiC powder of carbide ceramics with stainless steel powder and creating an overlay welding layer from this mixed powder, we can create chromium carbide and chromium-based materials in austenitic stainless steel and nickel-based alloy matrix. A metal structure in which carbides are crystallized is obtained, thereby suppressing cavitation, wear caused by solid substances, and combined damage thereof. These damage resistance effects cannot be exhibited unless 1% by volume of carbide ceramics is mixed with stainless steel and Ni-based alloy. However, for austenitic stainless steel, it is more than 40% by volume.
Since the stainless steel becomes more susceptible to cracking if two is added, the mixing amount is preferably 1 to 40% by volume based on the amount of stainless steel powder. On the other hand, since the amount of nickel, which is an austenite-forming element, increases with respect to nickel-based alloy powder, the mixed amount thereof can be up to 50% by volume.

In the present invention, SiC was selected because it has a cubic crystal structure similar to stainless steel, and because it relieves stress caused by centrifugal force in rotating parts, it has a lower density than stainless steel. In addition, S
This is because iC has a high standard energy for the carbide formation reaction, and by separating Sl and C, Si has been found to have the effect of promoting the formation of carbides of other elements, causing them to precipitate and crystallize in a network. This is because this net-like formation effect is exhibited in Cr carbide.

On the other hand, these build-up layers can effectively exhibit erosion resistance by imparting compressive residual stress to their surfaces by shot peening or the like. Furthermore, if the surface is treated by peening or the like, metal powder and the like from the treatment will remain on the surface of the built-up layer, so by removing the surface layer, loss resistance can be more effectively exhibited. In this case, if the surface layer is removed using emery paper with a moderate pressing force, compressive residual stress remains on the cut surface, which is effective in improving damage resistance, and the surface roughness is 10 μm or less. Should.

In addition, the erosion-resistant coating layer of the present invention, especially when considering a water turbine, contains 1% or less of sediment in river water in a steady state, but the steam coating layer contains 10% or less of sediment by weight. Useful against running water.

Equipment used in solid-liquid multiphase fluid media includes at least the runners, liners and nozzles of water turbines, steam and bin blades, ship propellers, impellers and liners of sand pumps, slurry transport pumps and piping, and their media. Effective for the surface of parts.

On the other hand, the base material on which the erosion-resistant coating layer of the present invention is formed can be any steel type that has good weldability, but it can be easily constructed using ordinary carbon steel, low alloy steel, martensitic stainless steel, or austenitic stainless steel. Cast stainless steel and forged steel are preferred.

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Example 1 Table 1 shows the compositions of the austenitic stainless steel powder or nickel-based alloy powder shown in the table (remaining Re) mixed with SiC powder (both average particle size 149 μm) at various volume ratios. Indicates the composition.

This mixture was welded using a powder plasma overlay welding device with an arc current of 220 to 25 OA and an arc voltage of 32 to 35 V.
With a width of 94 mm, the number of cycles is 15 to 16 cycles/min.
3 +++++++-layer build-up was carried out under welding conditions of shield 15.

The obtained overlay weld layer had a solidified structure in which composite carbides mainly composed of chromium were precipitated and crystallized in a network shape in a matrix. Figure 2 is a micrograph (magnification: 400x) of the overlay layer using No. 3 (Figure 2-A) and No. 4 (Figure 2-B) in Table 1, and shows the metallographic structure. Show, Si
No C particles were observed.

FIG. 1 shows the relationship between the Vickers hardness of the build-up layer and the amount added using the austenitic stainless steel powder No. 1 in Table 1 and various metal carbide powders.

Moreover, FIG. 7 shows the relationship between hardness and wear amount using the same built-up layer. At the same hardness, SiC has the least amount of wear.

FIG. 18 is a schematic sectional view of a commercially available plasma overlay welding device. At the start of operation, a pilot arc is generated by introducing plasma gas (Ar) 33 and passing a current between the W electrode (-) 31 and the matrix (+) 32, and then shielding gas (Ar) 34 is introduced. A voltage was applied between the flowing electrode 31 and the workpiece 32 to generate a plasma arc.

Then, a mixture 35 of powder (stainless steel powder + ceramic powder) and carrier gas (Ar) is supplied from a powder feeding device to a plasma arc 36, and the powder is transferred to the surface of the matrix 32 by plasma heat. was melted and welded to base 1 to form an overlay weld layer.

In addition, for comparison, a conventional overlay weld layer was constructed as follows. Table 2 shows the chemical composition of welding rods used in conventional covered arc welding.

Welding conditions are rod diameter 4 mmφ, current 150 A, voltage 23 V.
A 3 mm layer was deposited under the conditions of one person's heat of 16°C and KJ/cm.

In addition, in the construction of the overlay weld layer of the present invention and the overlay weld layer of the comparative material, the base material for both welds was made of N113Cr-containing cast steel (components are the same as N013 in Table 2) and was made of 25 txl OO.
A plate with dimensions mmxl 50mm was provided. After welding, a cavitation test piece (22φ: damaged surface) and an underwater earth and sand abrasion test piece (5t x 20mm x 50mm) were taken, and the test surfaces were finished with #1200 emery paper and used for testing.

Comparison of cavitation resistance in experiments was conducted using a magnetostrictive vibration type cavitation tester at a frequency of 6.5 KH.
z, the volume loss (cm
3) was evaluated.

On the other hand, the soil and sand abrasion resistance was tested and evaluated using a water jet test device containing soil and sand under the following conditions. Jet velocity 40 m/s
% collision angle is 45 deg, the soil is Al2O2 with an average particle size of 8 μm, its content is 30 g/j2, and the test time is 4
It was time. The amount of wear after the test was expressed as the volume loss (cm3) obtained by dividing the weight loss by the density.

Note that this device employs a method that can inject water containing earth and sand into the water, and is capable of generating cavitation. Therefore, a test was conducted using a cavitation coefficient of KO012 and K = 0.6, which can be expressed by the following equation.

This condition can cause combined damage of cavitation and soil abrasion.

However, V: Average jet velocity (m/s) g: Acceleration number of gravity (m/52) Pa: Atmospheric pressure (mAg) Pv: Vapor pressure (mAg) Pg: Fluid pressure (mAg) That is, K = 0. K=0.12 is a condition where damage is caused only by earth and sand abrasion, and K=0.12 is a condition where earth and sand abrasion and cavitation are combined.

Figure 3 shows the relationship between SiC content and wear amount due to earth and sand under the conditions of cavitation coefficient KO06 and 0.12. A represents the case where K = 0.6, and curve B represents the case of KO112.

Figure 4 shows Si measured using a magnetostrictive vibration cavitation tester.
The relationship between the amount of C added and cavitation weight loss is shown. Numbers 1 to 6 in the figure are Nos. 1 to 6 in Table 1. As the amount of SiC added increased, the hardness improved, and the amount of wear and cavitation loss tended to decrease. A comparison with the base material (point 1) shows that its damage resistance is greatly improved. In addition, when SiC is 40% by volume, a Vickers hardness of about 700 is obtained, and if more than this is added, the hardness is improved, but cracking is likely to occur.
is shown as the limit.

Figures 5 and 6 show soil abrasion tests and cavitation of the welded overlay of the present invention shown in Table 1 and the welded overlay of the comparative material shown in Table 2 under the condition of a 4/yavitation coefficient of 0.12. Showing the test results, sample No. in Table 1 and Table 2
The horizontal axis shows the amount of wear caused by earth and sand and the weight loss due to cavitation.

Inventive overlay welding layer No. 2 to 12 are comparative material No.
The amount of wear is significantly smaller than 1.13-17. Therefore, it is clear that the overlay weld layer of the present invention can be sufficiently effective for component parts where cavitation and damage caused by solid objects are a problem.

In addition, the mixed powder containing 40% of the SiC volume of the present invention was used on equipment members made of 5Ni13Cr cast steel, such as the guide vane 5 and the sheet liner 8 of a water turbine, as shown in the schematic diagrams of FIGS. 19 and 20. An overlay weld layer 1O was provided by overlay welding, annealed at 550 to 650°C, and then machined to a predetermined thickness (1 to 3 mm) to form the coating layer 10. In addition, overlay weld layers were similarly formed on the water turbine runner and cover liner. By forming this overlay weld layer, it was possible to prevent wear due to earth and sand, erosion due to cavitation, and combined damage thereof.

Example 2 Table 3 shows stainless steel particles with increased C and Si content (particle size 1
49 μm).

This powder is welded using a plasma overlay welding device with an arc current of 2
20-25 OA, arc voltage 32-35 V, ) - number of cycles 15-16 cycles/min at wiving width 94 mm, Ar
Gas supply rate (,11!/min) is plasma 3, carrier 5
3 ml was deposited under the welding conditions of shield 15, and the deposited weld layer was easily formed. Note that the base material contains Ni13
Cr (components are the same as No. 13 in Table 2) Cast steel (2
5tX]00mmX150mm) was used. the result,
As in Example 1, an overlay weld layer having a solidified structure in which composite carbides mainly composed of chromium were precipitated and crystallized in a network in the matrix was obtained.

As in Example 1, the obtained overlay weld layer of the present invention was subjected to a wear test by causing combined damage of cavitation and sand abrasion with a cavitation coefficient of 0.12.

FIG. 8 shows the amount of C added, and FIG. 9 shows the amount of Si added and the amount of wear due to earth and sand. The amount of soil abrasion decreases as the amount of C and Si added increases. C content is 0.3% or more, Si content is 3%
The effect will be greater if this is done.

However, when 4C is 2.5% and Si is 10% or more, the hardness shows a Vickers hardness of Hv=1000 or more, and in order to further increase the susceptibility to weld cracking, the present invention has a carbon content of 2.5% or more.
5%, and the Si content is shown as a limit of 10%.

Figures 10 and 11 show the overlay weld layers of the present invention (samples Nos. 19 to 22 and 24 to 29 in Table 3) and the overlay weld layers of comparative materials (samples Nos. 013 to 17 in Table 2, and No. 018 in Table 3).
and No. 23) shows the amount of wear caused by earth and sand and the weight loss due to cavitation. It is clear that the overlay weld layer of the present invention has superior damage resistance in both wear resistance and cavitation resistance compared to the comparative materials.

Example 3 The water turbine shown in Figures 12-A and 12-B was manufactured. Regarding the water-contacting surface (action surface P) side (FIG. 13B) of the water turbine runner shown in FIG. 12-A, the blade population length (
An overlay weld layer 10 was provided in a fan-shaped range (10) with a radius of 1/2 to 115 of L, ) (approximately 165+++ m). 1st
Regarding the back side of the action surface (reaction surface (R) side) of the water turbine runner shown in Figure 2B (Figure 13-A), the blade population length is determined with each of the blade ends (C, D) as the center. (L,
) (approximately 165 mm) (approximately 165 mm). to width (W
) 50 to 150 mm, 1/2 to 2/ of the blade outlet length L2
The overlay welding layer 12 was provided in the range of length (1) of the range of 3. These overlay welding layers were made using the same welding conditions as in Example 2 and using the mixed powder of No. 20 in Table 3, and then this layer was heated at 550°C to 550°C. 65
It was made by annealing at 0°C and then machining it to a thickness of 1-3 mm. The working surface side artificial end of the blade 3 (A,
The fan-shaped part (10) centered at B) is a part where wear is large due to running water containing earth and sand, and the fan-shaped part (11) centered at the artificial end (C, D) on the reaction surface side of the blade 3 is the outer outlet end. Both the portion extending from (E) corresponding to the overlay weld layer (12) are easily damaged by cavitation.

The guide vanes and sheet liners were the same as those shown in Example 1. Next, these parts were assembled to create a water wheel.

When this turbine was actually operated in running water containing sediment, it showed both excellent wear resistance and cavitation resistance.

Example 4 A Pelton water turbine shown in FIG. 14 was manufactured. A weld build-up layer 19 was provided on the circumferential surfaces of the tips of the needle valve 17 and nozzle valve 18 that inject the contained earth and sand water 20 shown in FIG. 14, and on the inner circumferential surface of the bucket 15 that receives the ejected water. The situation is shown in Figures 15 and 16. These overlay welding layers were made using the same welding conditions as in Example 1 and with N in Table 1.
o. Make a welded layer using the mixed powder of 5.
This layer was then annealed at 550°C to 650°C and then machined to a thickness of 1 to 3 mm. The joint space surface of the needle valve 17 and the nozzle valve 18 and the inner surface of the bucket 15 are areas that are subject to significant wear due to running water containing earth and sand.

When this turbine was actually operated with flowing water containing sediment, it showed both excellent soil abrasion resistance and anti-yavitation resistance.

Embodiment 5 Figures 17-A and 17-B show structural schematic diagrams of steam turbine rotor blades. The rotor blade 21 of this low pressure turbine final stage
In the prior art, a stellite plate was welded to the rotor blade tip 22, which is easily susceptible to erosion by water droplets, or a frame hardening treatment was applied to improve the hardness by heating the tip with a gas flame or the like. However, with the increase in capacity of turbines and the use of super blades, erosion due to water droplets is becoming more and more of a problem. Therefore,
As shown in Fig. 17-B, a rotor blade with a built-up coating layer 23 was manufactured using powder No. 25 shown in Table 3 of Example 2 of the present invention under the welding conditions shown in Example 1. Assembled.

After welding, it was reheated to 550°C to 650°C, annealed, and machined to a thickness of 1 to 3 mm.

When this moving blade was actually operated, excellent erosion resistance was obtained.

〔Effect of the invention〕

The erosion-resistant coating layer of the water turbine of the present invention is intended for equipment components that are damaged by cavitation caused by powder, sand and water, water droplets, slurry, etc., abrasion by solid objects, and a combination of these. Chromium carbide or composite carbide mainly composed of chromium is precipitated and crystallized in a mesh pattern in the overlay weld layer using a mixed powder of alloy powder and SiC powder, or austenitic stainless steel with increased C and Si content, or nickel-based alloy powder. Since a built-up layer with a solidified microstructure is formed on the surface of equipment components, cavitation, wear due to earth and sand, etc., and erosion due to water droplets can be suppressed, thereby preventing equipment from being eroded and reducing operational efficiency. We were able to reduce this and have a significant effect on improving its lifespan.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between metal carbide (volume %) and hardness (llv), Figure 2 is a micrograph showing the metal structure of the cross section of the overlay weld layer, and Figure 3 is the amount of SiC added. Fig. 4 is a graph showing the relationship between SiC addition amount and cavitation loss, Fig. 5 is a graph showing the amount of wear due to soil and sand, and Fig.
A graph comparing the amount of wear caused by earth and sand between the welded overlay layer of the present invention and a comparative material. Figure 6 is a graph comparing the cavitation loss between the welded overlay layer of the present invention and the comparative material. Figure 7 is a graph comparing the amount of wear due to earth and sand between the welded overlay layer of the present invention and the comparative material. A graph showing the relationship between hardness due to the addition of carbide and the amount of wear. Figure 8 is a graph showing the relationship between the 4C content and the amount of wear due to earth and sand. Figure 9 is a graph showing the relationship between the S1 content and the amount of wear due to earth and sand. , Fig. 10 is a graph comparing the amount of wear due to earth and sand between the welded overlay layer of the present invention and the comparative material, Fig. 11 is a graph comparing the cavitation loss between the welded overlay layer of the present invention and the comparative material, and Fig. 12A. 12B is a cross-sectional view showing the main part of a Francis turbine to which the overlay weld layer according to the present invention is applied, FIG. 12B is a perspective view of FIG. 12-A viewed from the X direction,
Figures 13-A and 13-B are views showing the locations where the coating layer is provided in the blade of a Francis turbine according to an embodiment of the present invention, and Figure 14 is a diagram showing where the overlay weld layer according to the present invention is applied. 15 and 16 are schematic diagrams of components of the Pelton turbine on which the overlay weld layer of the present invention is formed, and Figure 17-A is a cross-sectional view and a plan view showing the main parts of the Pelton turbine. Schematic diagram of a steam turbine rotor blade with a welded layer formed, 1st
Figure 7-B is a partially enlarged view of Figure 17-A, Figure 18 is a schematic diagram of the plasma arc welding device used to provide the overlay welding layer, Figures 19 and 20-A, and Figure 20- FIG. B is a schematic diagram of a Francis turbine component member on which a built-up weld layer of the present invention is formed. 1... Crown, 2... Shroud, 3... Vane, 4... Runner cone, 5... Guide vane, 6...
... Steben, 7... Runner liner, 8... Sea 1 to liner, 10... Overlay weld layer, 15... Bucket, 17... Needle, 18... Nozzle, 19...
・Build-up weld layer, ... moving blade, 2... erosion part, 3... build-up weld layer

Claims (1)

[Claims] 1. A coating material which is a weld overlay layer on the surface of a metal substrate made of an alloy containing at least one of Fe and Ni as a main component and 15 to 30% by weight of Cr. An erosion-resistant coating material having a metallic structure in which chromium carbide or a composite carbide mainly composed of chromium is crystallized in a network shape in an alloy matrix, and having a Vickers hardness (Hv) of 500 or less. 2. In a coating material that is a weld overlay layer on the surface of a metal substrate made of an alloy containing at least one of Fe and Ni as a main component and 15 to 30% by weight of Cr, in the matrix of the alloy, It has a metallic structure in which chromium carbide or composite carbide mainly composed of chromium crystallizes in a network shape, and contains 3 to 3 silicon.
An erosion-resistant coating material characterized by containing 10% by weight. 3. The coating material is a layer obtained by welding a mixed powder of austenitic stainless steel or nickel-based alloy powder and metal carbide powder, and the crystallized carbide is composed of austenitic stainless steel or nickel-based alloy. 2. The erosion-resistant coating material according to claim 1, wherein the erosion-resistant coating material is formed as a new phase of alloying elements. 4. The metal carbide part is made of SiC, Fe_3, which has a higher standard free energy of formation of carbide than the crystallized chromium carbide.
The erosion-resistant coating material according to claim 3, which is one or more selected from C, Ni_3C, CO_2C, or B_4C, and is contained in the weld build-up layer in an amount of 1 to 50% by volume. 5. The austenitic stainless steel or nickel-based alloy powder has C: 0.15% or less and Si:
0.2 to 1.0%, Mn: 15% or less, Ni: 50% or less, and Cr: 15 to 30%, or Co: 2
0% or less, Mo: 5% or less, Nb: 5% or less, Cu: 5
% or less, Ti: 5% or less, W: 5% or less, V: 5% or less, Al: 5% or less, N: 0.3% or less, and B: 0.01
The erosion-resistant coating material according to claim 3, wherein the erosion-resistant coating material contains at least one of % or less, and the remainder consists of Fe and accompanying unavoidable impurities. 6. C: 0.15% or less, Si: 0.2-1.
0%, Mn: 15% or less, Ni: 50% or less, Cr: 1
An erosion-resistant welding material consisting of an alloy powder of 5 to 30% by weight and the balance being Fe, and 5 to 15% by weight of SiC powder. 7. The weld build-up layer has a powder grain size (S) of the metal carbide and a powder grain size (M) of the austenitic stainless steel or nickel-based alloy each in the range of 10 to 200 μm and a grain size ratio S/M. 1 or less is laminated on the surface of an equipment member by plasma arc welding so that the thickness thereof is at least 5 mm or less.
5. The method for forming an erosion-resistant coating material according to 5. 8. The powder particle size of the austenitic stainless steel or nickel-based alloy is 10 to 200 μm.
A method of forming the erosion-resistant coating described. 9. A fluid device member, characterized in that the erosion-resistant coating material according to any one of claims 1 to 5 is formed on a surface of the fluid device member that is in contact with a multiphase flow of solid and liquid or gas. 10. The erosion-resistant coating material according to any one of claims 1 to 5 is used in a water turbine runner blade as a hydraulic machine,
Buckets, liners, guide vanes, nozzles, needles or seals, steam turbine blades or nozzles, coal,
Impellers, liners, piping or valves for sand or muddy slurry transport pumps, coal crushers, reheaters, heaters or aerators for coal-fired boilers, rolling rolls, marine screws, shovels for industrial or construction machinery. , bucket shells, tooth tips, excavation blades, striking blades, bulldozer rollers, earth removal plates, claws, hydraulic equipment and others, powder, sand and water,
Austenitic stainless steel containing 15 to 30% Cr by weight is used on parts and all surfaces of equipment components that are subject to erosion damage due to collisions, impacts, cutting, and scratching due to water droplets, oil, steam, slurry, aqueous solutions, and cavitation. Alternatively, various devices characterized in that a mixed powder of nickel-based alloy powder and at least SiC powder of metal carbide is melted by a plasma arc, supplied to the part to be welded, and formed into a desired thickness while creating a molten pool. Element.