CN113215565A - Laser composite manufacturing method for improving high-temperature oxidation resistance of steam turbine valve rod - Google Patents
Laser composite manufacturing method for improving high-temperature oxidation resistance of steam turbine valve rod Download PDFInfo
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- CN113215565A CN113215565A CN202110478433.8A CN202110478433A CN113215565A CN 113215565 A CN113215565 A CN 113215565A CN 202110478433 A CN202110478433 A CN 202110478433A CN 113215565 A CN113215565 A CN 113215565A
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C24/00—Coating starting from inorganic powder
- C23C24/08—Coating starting from inorganic powder by application of heat or pressure and heat
- C23C24/10—Coating starting from inorganic powder by application of heat or pressure and heat with intermediate formation of a liquid phase in the layer
- C23C24/103—Coating with metallic material, i.e. metals or metal alloys, optionally comprising hard particles, e.g. oxides, carbides or nitrides
- C23C24/106—Coating with metal alloys or metal elements only
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0075—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rods of limited length
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C19/00—Alloys based on nickel or cobalt
- C22C19/07—Alloys based on nickel or cobalt based on cobalt
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/10—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
- C23C14/14—Metallic material, boron or silicon
- C23C14/16—Metallic material, boron or silicon on metallic substrates or on substrates of boron or silicon
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
- C23C14/24—Vacuum evaporation
- C23C14/32—Vacuum evaporation by explosion; by evaporation and subsequent ionisation of the vapours, e.g. ion-plating
- C23C14/325—Electric arc evaporation
Abstract
The invention relates to a laser composite manufacturing method for improving high-temperature oxidation resistance of a steam turbine valve rod, which comprises the following steps: the first step is as follows: forming an atom metallurgically bonded cobalt-based alloy cladding layer with the thickness of 0.3-0.7mm on the surface of the valve rod by adopting laser cladding equipment and cobalt-based alloy powder; the second step is that: performing stress relief tempering on the valve rod to eliminate the fusion internal stress of part of dissimilar metals; the third step: turning to the final size of plus (0.05-0.10) mm grinding allowance; the fourth step: performing laser shock strengthening treatment on the surface of the cobalt-based alloy cladding layer; the fifth step: grinding and polishing to an assembly size; and a sixth step: physical vapor deposition of a (2-12) μm high temperature oxidation resistant coating (Cr-Al) at 1100 deg.C. The process solves the problem of frequent jamming of the valve rod of the steam turbine, and improves the safety and reliability of the steam turbine set.
Description
Technical Field
The invention relates to the technical field, in particular to a laser composite manufacturing method for improving the high-temperature oxidation resistance of a steam turbine valve rod.
Background
The valve rod material used on the main steam valve and the steam regulating valve of the original turbine is 12% Cr martensitic stainless heat-resistant steel (such as 20Cr12NiMoV1), and the surface of the valve rod is subjected to nitriding treatment after the quenching and tempering treatment; when the valve rod manufactured by the material and the process is used, the oxide skin of the valve rod grows too fast, so that the valve is jammed; the corrosion and oxidation of the 12% Cr martensitic stainless steel can occur under the long-time action of high-temperature (538 ℃ or 566 ℃) water vapor, and the high-temperature oxidation of the valve rod can be accelerated by a nitriding process; in the later stage, the GH901 alloy material is used for solid solution and aging treatment, and then surface nitriding treatment is carried out, so that the high-temperature oxidation resistance of the valve rod is improved, but the problem that the regulating valve is jammed due to the fact that oxide skin grows too fast and falls off under long-time high-temperature service of the valve rod is still not solved, and the safe operation of a steam turbine unit is restricted.
Disclosure of Invention
The invention aims to provide a laser composite manufacturing method for improving the high-temperature oxidation resistance of a steam turbine valve rod, which solves the problem of frequent jamming of the steam turbine set valve rod and improves the safety and reliability of the steam turbine set.
In order to achieve the purpose, the invention provides the following technical scheme: a laser composite manufacturing method for improving the high-temperature oxidation resistance of a steam turbine valve rod is characterized by comprising the following steps:
the first step is as follows: forming a metallurgically bonded cobalt-based alloy cladding layer with the thickness of 0.3-0.7mm on the surface of the valve rod by adopting laser cladding equipment and cobalt-based alloy powder;
the second step is that: performing stress relief tempering on the valve rod, and keeping the temperature for 3-8h to eliminate the fusion internal stress of part of dissimilar metals;
the third step: machining to a final size of + (0.05-0.10) mm grinding allowance;
the fourth step: performing laser shock strengthening treatment on the surface of the cobalt-based alloy cladding layer:
the fifth step: grinding and polishing to an assembly size;
and a sixth step: physical vapor deposition of a (2-12) μm high temperature oxidation resistant coating (Cr-Al) at 1100 deg.C.
Preferably, the cobalt-based alloy powder used in the first step is composed of, in mass fraction, 0.3 to 0.5% of carbon, 24 to 27% of chromium, 0.8 to 1.3% of iron, 0.4 to 0.6% of manganese, 0.7 to 1.2% of molybdenum, 9.5 to 12.0% of nickel, 0.3 to 0.4% of silicon, 7 to 9% of tungsten, and the balance of cobalt.
Preferably, the cobalt-based alloy powder used in the first step is composed of, in mass fraction, 0.40% of carbon, 25.5% of chromium, 1.0% of iron, 0.5% of manganese, 1.0% of molybdenum, 10.0% of nickel, 0.36% of silicon, 8.5% of tungsten, and the balance cobalt.
Preferably, the technical parameters of the laser cladding process are as follows: the diameter of a laser spot is 5mm, the power is 1400-2100W, the welding speed is 500mm/min, the lap joint rate is 50%, and the powder feeding amount is 15-22 g/min.
Preferably, the valve rod in the second step is made of 12% Cr martensitic stainless steel, and the stress relief tempering is performed at 520-580 ℃.
Preferably, the valve rod in the second step is a valve rod made of GH901 alloy material, and after stress relief tempering is carried out at 630-680 ℃.
Preferably, the specific parameters of the laser shock in the fourth step are as follows: the laser wavelength is 1.06 mu m, the pulse time is 22ns, the power is 8-10J, the spot diameter is 2.5mm, the frequency is 10Hz, flowing tap water is selected as a restraint layer, and black paint is selected as a light absorption coating.
Preferably, a 2-12 mu m Cr-Al coating resistant to high-temperature oxidation at 1100 ℃ is physically vapor deposited, and the specific process parameters are as follows: adopting a multi-arc ion plating technology, selecting argon with the purity of 99.99% as working gas, adopting a CrAl alloy target as a target material (the atomic percentage of Cr/Al is 1:1), grinding the surface of a workpiece step by using sand paper (No. 360, 600, 800, 1000, 1200 and 1500), polishing, ultrasonically cleaning the workpiece for 10-60min by absolute ethyl alcohol, drying and charging; vacuum chamber of furnace chamber is pumped to 8.0 x 10-3Setting the bias voltage of the workpiece support to be negative 500V below Pa, introducing Ar gas, and cleaning the surface of the workpiece for 30min and 60min by using the Ar gas and CrAl targets respectively; before depositing the Cr-Al working layer, adjusting the bias voltage to minus 100V, setting the current to be 100A, depositing a CrAl transition layer, and setting the deposition time to be 90min and the deposition thickness to be 0.5 mu m; when the coating is prepared, the temperature of a workpiece substrate is 400 ℃, and the bias voltage is negative50V, 100A of current, 3Pa of gas pressure and 12h of CrAl target deposition time.
The invention has the beneficial effects that:
the cobalt-based high-temperature alloy has excellent oxidation resistance in superheated steam at the temperature higher than 538 ℃, can be continuously used in an environment at the temperature of about 1000 ℃, is far better than a nickel-based alloy in oxidation resistance, but cobalt is an expensive metal and a sensitive strategic material, and is a process method for cladding a layer of cobalt-based alloy on the surface of a valve rod of a civil steam turbine by a laser cladding process method, so that the process method is a process method for realizing high performance improvement at low cost.
In order to further excavate the potential of cladding the cobalt-based alloy and eliminate the tensile stress hazard caused by the fusion of dissimilar metals in the laser cladding process, the valve rod of the 12% Cr martensitic stainless steel material is subjected to (520 plus 580) DEG C high-temperature stress relief tempering, and after the valve rod of the GH901 alloy material is subjected to (630 plus 680) DEG C high-temperature stress relief tempering, the laser shock strengthening process is carried out, so that the material surface layer is subjected to strain hardening while a dense and stable dislocation structure is formed on the material surface layer, and large compressive stress is remained, thereby remarkably improving the performances of the material such as fatigue resistance, stress corrosion resistance and the like.
In order to further prolong the service life of the valve rod of the steam turbine, a high-temperature oxidation resistant film (Cr-Al) with the thickness of 2-12 mu m is generated by adopting a physical vapor deposition method after the cobalt-based alloy cladding layer is finely ground and polished.
Tests prove that the high-temperature oxidation resistance of the valve rod prepared by the process is 30 times that of 12% Cr martensitic stainless steel subjected to quenching and tempering nitriding, and 10 times that of GH901 alloy material subjected to solid solution and ageing nitriding; the high temperature abrasion resistance is 3 times of that of the valve rod made of the martensitic stainless heat-resistant steel with 12 percent of Cr through quenching and tempering and nitriding. The expected service life is greatly prolonged, the problem of frequent jamming of the main steam and the adjusting valve rod is solved, and the safety and the reliability of the steam turbine set are improved.
Drawings
FIG. 1 is a comparison graph of microhardness gradients of cross sections of a conventional valve stem manufacturing process, example 1 and example 2;
FIG. 2 is a diagram of a test sample for high temperature oxidation resistance testing in a conventional valve stem manufacturing process, example 1 and example 2;
FIG. 3 shows the data of the high temperature oxidation resistance test in the conventional valve stem manufacturing process, example 1 and example 2;
FIG. 4 is a schematic view of a high temperature wear resistance test apparatus;
FIG. 5 is a graph of a high temperature wear test sample for a conventional valve stem fabrication process, example 1 and example 2;
FIG. 6 shows the data of the high temperature wear test in the conventional valve stem manufacturing process, example 1 and example 2;
FIG. 7 is a diagram of a sample of the conventional valve stem fabrication process, examples 1 and 2, for hot and cold shock resistance tests;
FIG. 8 shows the results of the cold and hot impact resistance tests of conventional valve stem fabrication processes, examples 1 and 2;
FIG. 9 is a scanning electron microscope image of a 1100 ℃ high temperature oxidation resistant coating (Cr-Al) of the composite process;
fig. 10 is a general flow chart of the composite process fabrication.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
(1) Adopting a laser cladding process, selecting cobalt-based alloy powder, and forming a metallurgically bonded cobalt-based alloy cladding layer with the thickness of 0.5mm on the surface of a valve rod made of 12% Cr martensitic stainless steel, wherein the technical parameters of the laser cladding process are as follows: the diameter of a light spot is 5mm, the laser power is 1800W, the welding speed is 500mm/min, the lap joint rate is 50 percent, and the powder feeding amount is 19 g/mim; the cobalt-based alloy comprises, by mass, 0.40% of carbon, 25.5% of chromium, 1.0% of iron, 0.5% of manganese, 1.0% of molybdenum, 10.0% of nickel, 0.36% of silicon, 8.5% of tungsten and the balance of cobalt;
(2) carrying out high-temperature stress relief tempering treatment at 560 ℃ on the valve rod made of the 12% Cr martensitic stainless steel material treated in the step (1), preserving heat for 6 hours, eliminating fusion internal stress of part of dissimilar metals, wherein the original thickness after cladding is about 1.0mm, and the residual effective thickness is 0.5mm after machining for about 0.5mm, so as to ensure that the valve rod is turned to the final size of the valve rod and the grinding allowance of 0.08 mm;
(3) performing laser shock strengthening treatment on the surface of the cobalt-based alloy cladding layer, wherein the specific parameters of the laser shock are as follows: the laser wavelength was 1.06 μm, the pulse time was 22ns, the power was 8J, the spot diameter was 2.5mm, and the frequency was 10 Hz. Selecting flowing tap water as a restraint layer, and using black paint as a light absorption coating; grinding, polishing to an assembly size, and carrying out hanging transportation and placement;
(4) and (4) carrying out physical vapor deposition on the valve rod obtained in the step (3) to form a 5-micron Cr-Al coating resistant to high-temperature oxidation at 1100 ℃.
Example 2
(1) Adopting a laser cladding process, preparing cobalt-based alloy powder, and forming a metallurgically bonded cobalt-based alloy cladding layer with the thickness of 0.5mm on the surface of the GH901 alloy material valve rod, wherein the technical parameters of the laser cladding process are as follows: the diameter of a light spot is 5mm, the laser power is 1900W, the welding speed is 500mm/min, the lap joint rate is 50 percent, and the powder feeding amount is 19 g/mim; the cobalt-based alloy comprises, by mass, 0.40% of carbon, 25.5% of chromium, 1.0% of iron, 0.5% of manganese, 1.0% of molybdenum, 10.0% of nickel, 0.36% of silicon, 8.5% of tungsten and the balance of cobalt;
(2) performing high-temperature stress relief tempering treatment at 660 ℃ on the GH901 alloy material valve rod treated in the step (1), preserving heat for 6 hours, eliminating partial dissimilar metal fusion internal stress, ensuring that the original thickness after cladding is about 1.0mm, and the residual effective thickness is 0.5mm after machining about 0.5mm, so as to ensure that the valve rod is turned to the final size of the valve rod plus 0.08mm grinding allowance;
(3) performing laser shock strengthening treatment on the surface of the cobalt-based alloy cladding layer, wherein the specific parameters of the laser shock are as follows: the laser wavelength was 1.06 μm, the pulse time was 22ns, the power was 8J, the spot diameter was 2.5mm, and the frequency was 10 Hz. Selecting flowing tap water as a restraint layer, and using black paint as a light absorption coating; grinding, polishing to an assembly size, and carrying out hanging transportation and placement;
(4) and (4) carrying out physical vapor deposition on the valve rod obtained in the step (3) to form a 5-micron Cr-Al coating resistant to high-temperature oxidation at 1100 ℃.
Example 3
(1) Adopting a laser cladding process, matching with cobalt-based alloy powder, forming a metallurgically bonded 0.7 mm-thick cobalt-based alloy cladding layer on the surface of a 12% Cr martensitic stainless steel valve rod, wherein the technical parameters of the laser cladding process are as follows: the diameter of a light spot is 5mm, the laser power is 2000W, the welding speed is 500mm/min, the lap joint rate is 50 percent, and the powder feeding amount is 22 g/mim; the cobalt-based alloy comprises, by mass, 0.5% of carbon, 24% of chromium, 1.3% of iron, 0.4% of manganese, 1.2% of molybdenum, 9.5% of nickel, 0.4% of silicon, 7% of tungsten and the balance of cobalt;
(2) carrying out high-temperature stress relief tempering treatment at 520 ℃ on the valve rod made of the 12% Cr martensitic stainless steel material treated in the step (1), preserving heat for 8 hours, eliminating fusion internal stress of part of dissimilar metals, wherein the original thickness after cladding is about 1.2mm, and the residual effective thickness is 0.7mm after machining for about 0.5mm, so as to ensure that the valve rod is turned to the final size of plus 0.10mm grinding allowance;
(3) performing laser shock strengthening treatment on the surface of the cobalt-based alloy cladding layer, wherein the specific parameters of the laser shock are as follows: the laser wavelength was 1.06 μm, the pulse time was 22ns, the power was 10J, the spot diameter was 2.5mm, and the frequency was 10 Hz. Selecting flowing tap water as a restraint layer, and using black paint as a light absorption coating; grinding, polishing to an assembly size, and carrying out hanging transportation and placement;
(4) and (4) carrying out physical vapor deposition on the valve rod obtained in the step (3) to form a 2-micron Cr-Al coating resistant to high-temperature oxidation at 1100 ℃.
Example 4
(1) Adopting a laser cladding process, matching with cobalt-based alloy powder, forming a metallurgically bonded 0.3 mm-thick cobalt-based alloy cladding layer on the surface of a 12% Cr martensitic stainless steel valve rod, wherein the technical parameters of the laser cladding process are as follows: the diameter of a light spot is 5mm, the laser power is 1400W, the welding speed is 500mm/min, the lap joint rate is 50 percent, and the powder feeding amount is 15 g/mim; the cobalt-based alloy comprises, by mass, 0.4% of carbon, 25% of chromium, 1.1% of iron, 0.48% of manganese, 0.9% of molybdenum, 11% of nickel, 0.34% of silicon, 7.5% of tungsten and the balance of cobalt;
(2) carrying out high-temperature stress relief tempering treatment at 580 ℃ on the valve rod made of the 12% Cr martensitic stainless steel material treated in the step (1), preserving heat for 6 hours, eliminating fusion internal stress of part of dissimilar metals, wherein the original thickness after cladding is about 0.8mm, and the residual effective thickness is 0.3mm after machining for about 0.5mm, so as to ensure that the valve rod is turned to the final size of the valve rod and the grinding allowance of 0.10 mm;
(3) performing laser shock strengthening treatment on the surface of the cobalt-based alloy cladding layer, wherein the specific parameters of the laser shock are as follows: the laser wavelength was 1.06 μm, the pulse time was 22ns, the power was 10J, the spot diameter was 2.5mm, and the frequency was 10 Hz. Selecting flowing tap water as a restraint layer, and using black paint as a light absorption coating; grinding, polishing to an assembly size, and carrying out hanging transportation and placement;
(4) and (4) carrying out physical vapor deposition on a 12-micron Cr-Al coating which resists the high-temperature oxidation at 1100 ℃ on the valve rod obtained in the step (3).
Example 5
(1) Adopting a laser cladding process, preparing cobalt-based alloy powder, and forming a metallurgically bonded cobalt-based alloy cladding layer with the thickness of 0.7mm on the surface of the GH901 alloy material valve rod, wherein the technical parameters of the laser cladding process are as follows: the diameter of a light spot is 5mm, the laser power is 2100W, the welding speed is 500mm/min, the lap joint rate is 50 percent, and the powder feeding amount is 22 g/mim; the cobalt-based alloy comprises, by mass, 0.35% of carbon, 26% of chromium, 1.2% of iron, 0.5% of manganese, 0.8% of molybdenum, 10.5% of nickel, 0.36% of silicon, 7.5% of tungsten and the balance of cobalt; (2) performing 630-DEG C high-temperature stress relief tempering treatment on the GH901 alloy material valve rod treated in the step (1), preserving heat for 5 hours, eliminating partial dissimilar metal fusion internal stress, ensuring that the original thickness after cladding is about 1.2mm, and the residual effective thickness is 0.7mm after machining about 0.5mm, so as to ensure that the valve rod is turned to the final size of the valve rod plus 0.08mm grinding allowance;
(3) performing laser shock strengthening treatment on the surface of the cobalt-based alloy cladding layer, wherein the specific parameters of the laser shock are as follows: the laser wavelength was 1.06 μm, the pulse time was 22ns, the power was 8J, the spot diameter was 2.5mm, and the frequency was 10 Hz. Selecting flowing tap water as a restraint layer, and using black paint as a light absorption coating; grinding, polishing to an assembly size, and carrying out hanging transportation and placement;
(4) and (4) carrying out physical vapor deposition on the valve rod obtained in the step (3) to form a 2-micron Cr-Al coating resistant to high-temperature oxidation at 1100 ℃.
Example 6
(1) Adopting a laser cladding process, preparing cobalt-based alloy powder, and forming a metallurgically bonded cobalt-based alloy cladding layer with the thickness of 0.3mm on the surface of the GH901 alloy material valve rod, wherein the technical parameters of the laser cladding process are as follows: the diameter of a light spot is 5mm, the laser power is 1500W, the welding speed is 500mm/min, the lap joint rate is 50 percent, and the powder feeding amount is 15 g/mim; the cobalt-based alloy comprises, by mass, 0.5% of carbon, 24% of chromium, 1.3% of iron, 0.4% of manganese, 1.2% of molybdenum, 9.5% of nickel, 0.4% of silicon, 7% of tungsten and the balance of cobalt;
(2) and (2) performing high-temperature stress relief tempering treatment at 680 ℃ on the GH901 alloy material valve rod treated in the step (1), preserving heat for 4 hours, eliminating part of dissimilar metal fusion internal stress, wherein the original thickness after cladding is about 0.8mm, and the residual effective thickness is 0.3mm after machining about 0.5 mm. Turning until the final size of the valve rod is plus 0.10mm grinding allowance;
(3) performing laser shock strengthening treatment on the surface of the cobalt-based alloy cladding layer, wherein the specific parameters of the laser shock are as follows: the laser wavelength was 1.06 μm, the pulse time was 22ns, the power was 9J, the spot diameter was 2.5mm, and the frequency was 10 Hz. Selecting flowing tap water as a restraint layer, and using black paint as a light absorption coating; grinding, polishing to an assembly size, and carrying out hanging transportation and placement;
(4) and (4) carrying out physical vapor deposition on a 12-micron Cr-Al coating which resists the high-temperature oxidation at 1100 ℃ on the valve rod obtained in the step (3).
And (3) detecting the surface stress state: actually measuring by XRD diffraction, wherein the surface of the cladding layer is in a tensile stress state of about 260MPA before laser shock strengthening; after strengthening, the surface is in a state of compressive stress, and the effective depth of the compressive stress is about 0.7mm at negative 410 MPA.
And (3) section hardness gradient detection: the hardness gradient comparison is carried out on the samples obtained in the embodiment 1 and the embodiment 2 and the sample quenched, tempered and nitrided in the conventional process, 3 samples are tested in parallel in a single test, the average value is taken to obtain a figure 1, the figure can be obviously obtained through pictures, and after the samples are treated by the process, the physical vapor deposition Cr-Al with high temperature oxidation resistance is obtained through physical vapor depositionThe hardness (0.005mm depth) of the coating can reach 2800HV0.005Much higher than the hardness of the nitrided surface layer (600 HV)0.3) Hardness of the cladding layer is more than 310HV0.3The depth is about 0.5mm, the nitriding depth is about 0.3-0.4mm larger than 20Cr12NiMoV1, and the nitriding depth of GH901 is about 0.10 mm.
And (3) detecting the high-temperature oxidation resistance: according to the processes of the embodiment 1 and the embodiment 2 of the invention, two groups of 2 cylindrical samples are respectively manufactured, 2 groups of 2 cylindrical samples made of 20Cr12NiMoV1 and GH901 materials through quenching and tempering and nitriding are simultaneously manufactured, a 304 stainless steel net is used as a tray (figure 2), the four groups of 8 samples are put into a resistance furnace at 750 ℃ for heat preservation and timing, the samples are weighed at intervals of 0h, 5h, 20h, 40h, 70h and 175h, and the high-temperature oxidation weight gain is calculated, so that a result figure 3 is obtained. The high temperature oxidation resistance of the sample prepared by the composite process is obviously about 10 times higher than that of GH901 nitridation in the conventional process.
And (3) detecting the high-temperature wear resistance: four sets of samples (FIG. 5) of 25mm diameter were made according to ASTM G98-17 standard (FIG. 4) and tested for high temperature wear resistance: the average weight loss of samples made of 20Cr12NiMoV1 and GH901 materials after quenching and tempering and nitriding is about 3 times of that of the samples made by the corresponding composite process (figure 6), and the high-temperature wear resistance of the samples processed by the process is greatly improved.
And (3) detecting the cold and hot impact resistance: respectively manufacturing two groups of 3 cylindrical samples according to the processes of the embodiment 1 and the embodiment 2, simultaneously manufacturing 2 groups of 3 cylindrical samples made of 20Cr12NiMoV1 and GH901 materials through quenching and tempering and nitriding, putting the cylindrical samples into an electric furnace at 600 ℃ for heating and heat preservation for 15min, taking out the cylindrical samples and putting the cylindrical samples into flowing tap water for quick cooling; in such a cycle, the average number of cracks on the surface of the sample is counted to obtain the crack appearance shown in fig. 7 and the crack data statistical chart shown in fig. 8, and the results can be obviously obtained through fig. 7-8, so that the sample treated by the process has more excellent cold and hot impact resistance, and the cracking risk of the valve sealing surface in the use process is reduced.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Claims (7)
1. A laser composite manufacturing method for improving the high-temperature oxidation resistance of a steam turbine valve rod is characterized by comprising the following steps:
the first step is as follows: forming an atom metallurgically bonded cobalt-based alloy cladding layer with the thickness of 0.3-0.7mm on the surface of the valve rod by adopting laser cladding equipment and cobalt-based alloy powder;
the second step is that: performing stress relief tempering on the valve rod, and keeping the temperature for 3-8h to eliminate the fusion internal stress of part of dissimilar metals;
the third step: turning to the final size of plus (0.05-0.10) mm grinding allowance;
the fourth step: performing laser shock strengthening treatment on the surface of the cobalt-based alloy cladding layer:
the fifth step: grinding and polishing to an assembly size;
and a sixth step: physical vapor deposition of a (2-12) μm thick coating (Cr-Al) resistant to high temperature oxidation at 1100 ℃.
2. The laser composite manufacturing method for improving the high-temperature oxidation resistance of the steam turbine valve rod according to claim 1, wherein the cobalt-based alloy powder used in the first step consists of, by mass, 0.3-0.5% of carbon, 24-27% of chromium, 0.8-1.3% of iron, 0.4-0.6% of manganese, 0.7-1.2% of molybdenum, 9.5-12.0% of nickel, 0.3-0.4% of silicon, 7-9% of tungsten, and the balance of cobalt.
3. The laser composite manufacturing method for improving the high-temperature oxidation resistance of the steam turbine valve rod according to claim 2, wherein the cobalt-based alloy powder adopted in the first step consists of, by mass, 0.40% of carbon, 25.5% of chromium, 1.0% of iron, 0.5% of manganese, 1.0% of molybdenum, 10.0% of nickel, 0.36% of silicon, 8.5% of tungsten and the balance cobalt.
4. The laser composite manufacturing method for improving the high-temperature oxidation resistance of the steam turbine valve rod according to claim 1, is characterized in that the technical parameters of a laser cladding process are as follows: the diameter of a laser spot is 5mm, the power is 1400-2100W, the welding speed is 500mm/min, the lap joint rate is 50%, and the powder feeding amount is 15-22 g/min.
5. The laser composite manufacturing method for improving the high-temperature oxidation resistance of the valve rod of the steam turbine as claimed in claim 1, wherein the valve rod in the second step is made of 12% Cr martensitic stainless steel material and is subjected to stress relief tempering at 520 ℃ and 580 ℃.
6. The laser composite manufacturing method for improving the high-temperature oxidation resistance of the steam turbine valve rod as claimed in claim 1, wherein the valve rod in the second step is a valve rod made of GH901 alloy material, and is subjected to stress relief tempering at 630-680 ℃.
7. The laser composite manufacturing method for improving the high-temperature oxidation resistance of the steam turbine valve rod according to claim 1, wherein the specific parameters of the laser shock in the fourth step are as follows: the laser wavelength is 1.06 mu m, the pulse time is 22ns, the power is 8-10J, the spot diameter is 2.5mm, the frequency is 10Hz, flowing tap water is selected as a restraint layer, and black paint is selected as a light absorption coating.
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