CN110699614B

CN110699614B - B-C-N-O supersaturated solid solution austenitic stainless steel powder and preparation and cladding methods

Info

Publication number: CN110699614B
Application number: CN201911063932.XA
Authority: CN
Inventors: 邱长军; 宋勇; 陈勇; 朱红梅; 张振远; 张聪; 朱伟
Original assignee: Nanhua University
Current assignee: Nanhua University
Priority date: 2019-11-04
Filing date: 2019-11-04
Publication date: 2021-08-06
Anticipated expiration: 2039-11-04
Also published as: CN110699614A

Abstract

The invention discloses B-C-N-O supersaturated solid solution austenitic stainless steel powder and a preparation and cladding method thereof, wherein the powder consists of the following elements: 0.40-0.48% of C, 18.5-19.0% of Cr18.0%, 8.0-9.0% of Ni0.001-0.006% of B, 0.80-0.95% of Si, 0.08-0.12% of N, 0.045-0.055% of O and the balance of Fe; carrying out vacuum melting and powdering on the elements in proportion under high-purity nitrogen atomization; the prepared powder adopts a cladding method of rapid cooling induced nonequilibrium phase change in a laser melting pool, and technological parameters of laser energy density, scanning speed, powder feeding speed and lap joint coefficient are limited; the invention realizes the obvious strengthening effect of 18-8 type austenitic stainless steel interstitial atoms on the premise of ensuring that the corrosion resistance and the plastic toughness are not reduced.

Description

B-C-N-O supersaturated solid solution austenitic stainless steel powder and preparation and cladding methods

Technical Field

The invention belongs to the technical field of laser additive and remanufacture, and relates to B-C-N-O atom supersaturated solid-solution austenitic stainless steel powder and a preparation and cladding method thereof.

Background

The 18-8 type austenitic stainless steel is widely applied to various industries due to the excellent corrosion resistance and good comprehensive mechanical property. However, the defects of low strength, poor creep resistance and the like of the 18-8 type austenitic stainless steel limit the application of the austenitic stainless steel in the field with high strength and excellent plasticity and toughness. Therefore, on the premise of not reducing the corrosion resistance and the plastic toughness, the key point for expanding the application field of the 18-8 type austenitic stainless steel is to greatly improve the strength.

Based on conventional knowledge, carbon atoms have always played an important role in the strengthening of plain carbon steelsColor, but carbon atoms have been considered harmful and avoided to the utmost in austenitic and a/F duplex stainless steels. The fundamental reason is that the equilibrium solubility of carbon in austenite is extremely small, and the carbon is easy to segregate in grain boundary to form M₂₃C₆The phases, which produce the well-known chromium-poor regions of grain boundaries, have catastrophic consequences such as a sharp drop in corrosion resistance. On the other hand, in the laser metal additive manufacturing process under the atmospheric environment, the oxidation of the alloy is avoided as much as possible and high requirements are put on the oxygen content of the alloy powder, mainly because the equilibrium solubility of oxygen in the alloy is low, and excessive oxygen doping can cause the oxygen to be segregated at grain boundaries, crack tips, dislocations and other internal stress sources to form significant stress concentration or form ultra-nano-scale brittle oxide ceramic phases to induce catastrophic metal brittle fracture. As long as interstitial atoms can exist in the alloy in a supersaturated form which is not deviated to form obvious stress concentration and no ultra-nano scale brittle ceramic phase transformation, the strengthening and toughening effect with engineering application value can be obtained.

Disclosure of Invention

In order to achieve the aim, the invention provides B-C-N-O supersaturated solid solution austenitic stainless steel powder, which solves the problem of low strength of 18-8 type austenitic stainless steel in the prior art.

Another object of the present invention is to provide a process for the preparation of the above-mentioned powders.

The invention further aims to provide a cladding method of the powder.

In order to solve the technical problems, the invention adopts the technical proposal that,

a B-C-N-O supersaturated solid solution austenitic stainless steel powder comprises the following elements in percentage by mass:

0.40-0.48% of C, 18.5-19.0% of Cr, 8.0-9.0% of Ni, 0.001-0.006% of B, 0.80-0.95% of Si, 0.08-0.12% of N, 0.045-0.055% of O and the balance of Fe, wherein the sum of the mass percentages is 100%.

Further, the powder consists of the following elements in percentage by mass: 0.46 percent of C, 18.71 percent of Cr, 8.37 percent of Ni0.001 percent of B, 0.85 percent of Si, 0.11 percent of N, 0.045 percent of O and the balance of Fe, wherein the sum of the mass percentages is 100 percent.

The other technical scheme of the invention is a preparation method of B-C-N-O supersaturated solid solution austenitic stainless steel powder, which comprises the following steps: according to the mass percent of each element of the powder, 0.40-0.48 percent of C, 18.5-19.0 percent of Cr, 8.0-9.0 percent of Ni, 0.001-0.006 percent of B and 0.80-0.95 percent of Si, selecting intermediate transition alloy iron carbon, iron chromium, iron silicon, ferroboron and pure nickel to prepare an alloy mixture with required proportion components, carrying out vacuum melting on the alloy mixture, carrying out atomization powder preparation by using high-purity nitrogen, wherein the nitrogen content of the powder is 0.08-0.12 percent and the oxygen content is 0.045-0.055 percent, and screening out powder with the granularity of 50-180 mu m to obtain supersaturated solid solution austenitic stainless steel powder for B-C-N-O, wherein the powder is high-performance austenitic stainless steel powder for generating B-C-N-O atomic solid solution strengthening and toughening effects by laser forming.

Further, the powder consists of the following elements in percentage by mass: 0.46 percent of C, 18.71 percent of Cr, 8.37 percent of Ni, 0.001 percent of B, 0.85 percent of Si, 0.11 percent of N, 0.045 percent of O and the balance of Fe, wherein the sum of the mass percentages is 100 percent.

The other technical scheme of the invention is a cladding method of B-C-N-O supersaturated solid solution austenitic stainless steel powder, which comprises the following steps: the method comprises the steps of carrying out laser cladding on the powder prepared by atomizing high-purity nitrogen to prepare powder, carrying out rapid cooling induction non-equilibrium phase change cladding on B-C-N-O supersaturated solid solution austenitic stainless steel powder in a laser molten pool, adopting a circulating water-cooled air curtain cover to protect a laser synchronous lateral powder feeding nozzle device, placing a base material subjected to sand blasting treatment on a circulating water cooling device, determining a laser scanning track by controlling an experimental worktable, adjusting the distance between a nozzle of a laser and the base material, and cladding the laser-formed high-performance austenitic stainless steel powder on the surface of the base material by adopting a lateral synchronous powder feeding method, thus obtaining the austenitic stainless steel laser cladding layer with high strength, excellent plasticity and corrosion resistance.

Further, the laser treatment process conditions are as follows: laser energy density of 300-500W/mm²The scanning speed is 6-9 mm/s, the powder feeding speed is 3-5 g/min,the lapping coefficient is 0.5, and the protective gas is high-purity nitrogen, so that the austenitic stainless steel laser cladding layer with high strength, excellent plasticity and corrosion resistance can be prepared.

0.40-0.48% of C, and low mechanical property caused by low carbon content; if the carbon content is too high, the ductility and toughness are poor, M23C6 is easy to precipitate, and the corrosion resistance is reduced due to the formation of grain boundary chromium depletion. By properly increasing the carbon content of the powder, the mechanical property of the laser forming layer is improved on the premise of ensuring higher post-fracture elongation and excellent corrosion resistance of the laser forming layer. 18.5-19.0% of Cr, too low chromium content and poor corrosion resistance of a laser forming layer; an increase in the chromium content increases the corrosion resistance, but the corresponding costs increase, while an increase in the N content likewise increases the corrosion resistance, so that there is no need for an increase in the chromium content. 8.0-9.0% of Ni: the nickel content is too low to form austenite; the nickel content is too high, the corresponding powder cost is too high, and the industrial popularization is not facilitated. B is 0.001-0.006%: the proper boron content can enhance the slagging and oxidation resistance of a molten pool, but the too high boron content can sharply reduce the elongation; the range can effectively enhance the slagging and oxidation resistance of the molten pool and realize that the laser forming layer prepares the austenitic stainless steel layer with high mechanical property. 0.80-0.95% of Si: reducing agent and deoxidizing agent to strengthen slag-making performance of molten pool, and if too low, it will have too high requirement on gas atomizing powder-making equipment, and if too high, its plasticity and toughness will be lower. 0.08-0.12% of N: the nitrogen element is an austenite forming element and can strongly stabilize an austenite phase; the mechanical property is effectively improved on the premise of ensuring that the plasticity and toughness of the laser forming layer are not obviously reduced. 0.045-0.055%: the oxygen content is low, the gas atomization powder preparation and laser forming process and the cost are too high; the oxygen content is too high, so that a brittle oxide ceramic phase is easily formed, and brittle fracture is induced; in the range, the laser forming layer with high mechanical property, plastic toughness and excellent corrosion resistance can be effectively prepared on the premise of greatly reducing the harsh powder preparation process and laser forming process requirements.

During laser forming, the molten pool is cooled quickly to induce the B-C-N-O four kinds of interstitial atoms to be supersaturated and dissolved in austenite of a surface center structure, and a self-organization interstitial atom short-range combination unit in a lower energy state is formed through short-range migration.

In the cladding method of B-C-N-O supersaturated solid-solution austenitic stainless steel powder, the laser energy density is 300-500W/mm²The scanning speed is 6-9 mm/s, the powder feeding speed is 3-5 g/min, and the overlap joint coefficient is 0.5', and the series of process parameters can ensure that the stable high-performance austenitic stainless steel layer can be effectively prepared in the laser forming process. Over-burning can occur when the laser energy density is too high; otherwise, the powder cannot be melted through. The scanning speed and the powder feeding speed can realize the matching adjustment of the laser energy density range within the above range; the probability of inclusion of a forming layer is too high when the overlapping rate is too high, the overlapping rate is too low, and the laser forming efficiency is low; under the laser process parameters, the austenitic stainless steel powder and the laser cladding method can realize the solid solution strengthening and toughening effects of B-C-N-O interstitial atoms and prepare the high-performance austenitic stainless steel layer.

The intermediate transition alloy of iron carbon, iron chromium, iron silicon, ferroboron and pure nickel is selected, the transition alloy is only required to be mixed to match 0.40-0.48% of C, 18.5-19.0% of Cr, 8.0-9.0% of Ni, 0.001-0.006% of B and 0.80-0.95% of Si, and Fe with corresponding content, the mixed powder is subjected to vacuum melting, and then high-purity nitrogen gas atomization powder preparation is carried out (in the process, N is controlled to be 0.08-0.12% and O is controlled to be 0.045-0.055%) on the mixed powder, and the added transition alloy must ensure that P is less than or equal to 0.01%, S is less than or equal to 0.01% and O is controlled to be 0.045-0.055% in the powder after gas atomization powder preparation.

Vacuum melting and gas atomization are powder preparation methods in which metal liquid formed by alloy mixing melting is impacted by fast moving fluid (atomizing medium: high-purity nitrogen) or is formed into fine liquid drops in other modes under the vacuum condition, and then the fine liquid drops are condensed into solid powder.

The vacuum melting technology is a special melting technology for melting metal and alloy under the vacuum condition. Can effectively remove gas, non-metallic inclusions and non-ferrous metal impurities in the alloy and improve the purity of the alloy.

Gas atomization is a technology for preparing high-purity superfine metal powder by adopting advanced vacuum induction melting and inert gas atomization technologies. Specifically, when the powder is prepared by gas atomization, a metal raw material is firstly smelted into alloy liquid with qualified components by using an induction furnace (generally overheated by 100-150 ℃), and then the alloy liquid is injected into a tundish above an atomizing nozzle. The alloy liquid flows out from a leak hole at the bottom of the tundish, meets high-speed airflow when passing through the nozzle and is atomized into fine droplets, and the atomized droplets are rapidly solidified into alloy powder in the closed atomizing cylinder. Atomization is the best method for producing fully alloyed powders, the product of which is known as pre-alloyed powder. Each particle of this powder not only has exactly the same uniform chemical composition as a given molten alloy, but also, due to the rapid solidification, refines the crystalline structure and eliminates the macrosegregation of the second phase.

The stable supersaturated solid solution of the interstitial atoms is obtained by combining and proportioning the interstitial atoms in the austenitic stainless steel powder and rapidly cooling the laser molten pool, and the method is mainly characterized in that the carbon content in the 18-8 type austenitic stainless steel is increased to 0.4-0.48%, and the interstitial strengthening effect of the carbon atoms is fully exerted; trace B and a proper amount of N, O elements are added to form the combination ratio of four interstitial atoms B-C-N-O; in the atmospheric environment, high-purity nitrogen protects laser forming, the rapid cooling of a laser molten pool can induce four interstitial atoms B-C-N-O to be supersaturated and dissolved in austenite of a surface-centered structure during forming, the discretely distributed interstitial atoms can form a self-organized interstitial atom short-range combination unit in a lower energy state through short-range migration according to a dissipation structure theory, the interstitial atom short-range combination unit has higher stability, the segregation of the interstitial atoms at grain boundaries, crack tips, dislocations and other internal stress sources and the formation of a grain boundary super-nanoscale brittle ceramic phase are avoided, and the obvious strengthening effect of the interstitial atoms of the 18-8 type austenitic stainless steel is realized on the premise of ensuring that the corrosion resistance and the plastic toughness are not reduced. The method has important significance for greatly improving the strength of the widely used 18-8 type austenitic stainless steel on the premise of ensuring the corrosion resistance and the plastic toughness.

The invention has the beneficial effects that: under the atmosphere, under the protection of high-purity nitrogen, the tensile strength of a formed sample prepared by adopting a laser molten pool rapid cooling induced non-equilibrium phase change technology (the nitrogen content can reach 0.11-0.13%, the carbon content can reach 0.38-0.47%, and the oxygen content is controlled to be 0.050-0.060%) reaches 961 +/-40 MPa, the yield strength reaches 671 +/-20 MPa, and the elongation reaches 37.5 +/-3%. The tensile strength and the yield strength of the stainless steel are about 1.4-1.5 times of those of AISI304 stainless steel, and the corrosion resistance of the stainless steel is better than that of AISI 304; no B-C-N-O interstitial atom precipitated phase appears in the molded sample after air cooling within 500 ℃ for 2h, the room-temperature mechanical property is not obviously changed, and the corrosion resistance is slightly lower than that of the laser molded sample but still higher than AISI 304.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1a is a diagram of a laser molten pool rapid cooling cladding layer preparation.

FIG. 1b is a drawing of a wire cut sample draw position.

Figure 1c is a drawing of the dimensions of a tensile specimen.

Fig. 2a is a diagram of a cladding layer sample OM.

FIG. 2b is a graph of OM after air cooling at 300 ℃ for 2 h.

FIG. 2c is a graph of OM after 500 ℃ x 2h air cooling.

FIG. 2d is a graph of OM after 700 ℃ x 2h air cooling.

Fig. 3 is an XRD quantitative analysis spectrum.

FIG. 4 is a graph of the distribution of a 3DAP atom probe (300 ℃ C.. times.2 h air-cooled sample).

FIG. 5a is a SEM/EDS surface scanning energy spectrum of a cladding layer sample after 500 ℃ for 2h air cooling.

FIG. 5b is a SEM/EDS line scan energy spectrum of a cladding layer sample after 500 ℃ x 2h air cooling (high magnification and element fluctuation on line "data 3").

FIG. 5c is a SEM/EDS line scan energy spectrum (lower magnification) of a cladding layer sample after 500 ℃ x 2h air cooling.

FIG. 5d is a SEM/EDS line scan energy spectrum of the cladding layer sample after 500 ℃ x 2h air cooling (high magnification and element fluctuation on line "data 2").

FIG. 6a is a TEM bright field image of a cladding layer sample.

FIG. 6b is a TEM bright field image of a cladding sample.

FIG. 6c is a TEM bright field image of a cladding sample.

FIG. 6d is a TEM bright field image of a cladding sample.

FIG. 7a is a TEM grain boundary image (diffraction spot at macroscopic magnification) of a cladding layer sample.

FIG. 7b is a TEM crystal structure of a cladding sample (diffraction spots in the (1, 1, 0) direction).

FIG. 7c is a TEM crystal structure of a cladding sample (marked by two larger diffraction spots in the (1, 1, 0) direction).

FIG. 7d is a TEM crystal structure of a cladding sample (marked by a smaller diffraction spot in the (1, 1, 0) direction).

FIG. 8 is a stress-strain graph of a cladding specimen.

FIG. 9a is a SEM fracture view of a cladding layer sample.

FIG. 9b is a SEM micrograph at 300 ℃ for 2h after air cooling.

FIG. 9c is a SEM micrograph taken after 500 ℃ 2h air cooling.

FIG. 9d is a SEM micrograph taken after 700 ℃ 2h air cooling.

FIG. 10 electrochemical corrosion cathodic polarization curve.

FIG. 11 synchrotron radiation short range ordered detection results.

FIG. 12 is a graph comparing the stress/strain curves of examples 1-6.

Fig. 13 is an octahedral gap position diagram.

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

Step S1, the supersaturated solid-solution austenitic stainless steel powder of B-C-N-O comprises the following elements in percentage by mass: 0.40% of C, 18.5% of Cr, 8.0% of Ni, 0.001% of B, 0.85% of Si, 0.08% of N, 0.045% of O and the balance of Fe, wherein the sum of the mass percentages is 100%;

step S2, selecting intermediate transition alloy iron carbon, iron chromium, iron silicon, ferroboron and pure nickel according to the mass percentage of the alloy elements to prepare an alloy mixture with the proportional components, carrying out vacuum melting on the alloy mixture, carrying out atomization powder preparation by using high-purity nitrogen, the nitrogen content of the powder in the powder preparation process is 0.08 percent, the oxygen content is 0.045 percent, the powder with the granularity of 50-180 mu m is screened (the screened powder can only be in one grain size interval, but can not be in the same grain size, the grain size of the powder is screened to be 50-180 mu m, and the effective laser cladding process can be ensured when the grain size interval of the powder special for laser forming is met), thus obtaining the B-C-N-O supersaturated solid solution austenitic stainless steel powder which is used for laser forming to generate the solid solution strengthening and toughening effect of B-C-N-O atoms.

Step S3, as shown in FIG. 1, the prepared B-C-N-O supersaturated solid solution austenitic stainless steel powder is clad in a laser melting bath by adopting a rapid cooling induction non-equilibrium phase change cladding method, a circulating water cooling air curtain cover is used for protecting a laser synchronous lateral powder feeding nozzle device, a base material subjected to sand blasting treatment is placed on a circulating water cooling device, then a laser scanning track is determined by controlling an experimental worktable, the distance between a nozzle of a laser and the base material is adjusted, and the laser forming high-performance austenitic stainless steel powder is clad on the surface of the base material by adopting a lateral synchronous powder feeding method, so that the austenitic stainless steel laser cladding layer with high strength, excellent plasticity and corrosion resistance can be prepared, wherein the laser energy density is 300W/mm²The scanning speed is 6mm/s, the powder feeding speed is 3g/min, the lapping coefficient is 0.5,the protective gas is high-purity nitrogen.

Example 2

Step S1, the supersaturated solid-solution austenitic stainless steel powder of B-C-N-O comprises the following elements in percentage by mass: 0.44% of C, 18.7% of Cr, 8.5% of Ni, 0.002% of B, 0.83% of Si, 0.10% of N, 0.05% of O and the balance of Fe, wherein the sum of the mass percentages is 100%;

and step S2, selecting intermediate transition alloys of iron carbon, iron chromium, iron silicon, ferroboron and pure nickel according to the mass percent of the alloy elements to prepare an alloy mixture of the components, carrying out vacuum melting on the alloy mixture, atomizing the alloy mixture by using high-purity nitrogen to prepare powder, wherein the nitrogen content and the oxygen content of the powder are respectively 0.10% and 0.05%, and sieving the powder with the granularity of 50-180 mu m to prepare the B-C-N-O supersaturated solid solution austenitic stainless steel powder which is used for laser forming to generate the B-C-N-O atomic solid solution strengthening and toughening effect.

Step S3, as shown in FIG. 1, the prepared B-C-N-O supersaturated solid solution austenitic stainless steel powder is clad in a laser melting bath by adopting a rapid cooling induction non-equilibrium phase change cladding method, a circulating water cooling air curtain cover is used for protecting a laser synchronous lateral powder feeding nozzle device, a base material subjected to sand blasting treatment is placed on a circulating water cooling device, then a laser scanning track is determined by controlling an experimental worktable, the distance between a nozzle of a laser and the base material is adjusted, and the laser forming high-performance austenitic stainless steel powder is clad on the surface of the base material by adopting a lateral synchronous powder feeding method, so that the austenitic stainless steel laser cladding layer with high strength and excellent plasticity and corrosion resistance can be prepared, wherein the laser energy density is 400W/mm²The scanning speed is 7mm/s, the powder feeding speed is 4g/min, the lapping coefficient is 0.5, and the protective gas is high-purity nitrogen.

Example 3

Step S1, the supersaturated solid-solution austenitic stainless steel powder of B-C-N-O comprises the following elements in percentage by mass: 0.48 percent of C, 19.0 percent of Cr, 9.0 percent of Ni, 0.006 percent of B, 0.95 percent of Si, 0.12 percent of N, 0.55 percent of O and the balance of Fe, wherein the sum of the mass percentages is 100 percent;

and step S2, selecting intermediate transition alloy iron carbon, iron chromium, iron silicon, ferroboron and pure nickel according to the mass percent of the alloy elements to prepare an alloy mixture of the components, carrying out vacuum melting on the alloy mixture, atomizing the alloy mixture into powder by using high-purity nitrogen, wherein the nitrogen content of the powder is 0.12 percent, the oxygen content of the powder is 0.055 percent in the powder preparation process, and sieving the powder with the granularity of 50-180 mu m to obtain the B-C-N-O supersaturated solid solution austenitic stainless steel powder which is used for laser forming to generate the B-C-N-O atomic solid solution strengthening and toughening effect.

Step S3, as shown in figure 1, the prepared B-C-N-O supersaturated solid solution austenitic stainless steel powder is clad in a laser melting bath by adopting a rapid cooling induction non-equilibrium phase change cladding method, a circulating water cooling air curtain cover is used for protecting a laser synchronous lateral powder feeding nozzle device, a base material subjected to sand blasting treatment is placed on a circulating water cooling device, then a laser scanning track is determined by controlling an experimental worktable, the distance between a nozzle of a laser and the base material is adjusted, and the laser forming high-performance austenitic stainless steel powder is clad on the surface of the base material by adopting a lateral synchronous powder feeding method, so that the austenitic stainless steel laser cladding layer with high strength and excellent plasticity and corrosion resistance can be prepared, wherein the laser energy density is 450W/mm²The scanning speed is 9mm/s, the powder feeding speed is 5g/min, the lapping coefficient is 0.5, and the protective gas is high-purity nitrogen.

Example 4

Step S1, the supersaturated solid-solution austenitic stainless steel powder of B-C-N-O comprises the following elements in percentage by mass: 0.46% of C, 18.71% of Cr, 8.37% of Ni, 0.001% of B, 0.85% of Si, 0.11% of N, 0.045% of O and the balance of Fe, wherein the sum of the mass percentages is 100%;

and step S2, selecting intermediate transition alloys of iron carbon, iron chromium, iron silicon, ferroboron and pure nickel according to the mass percent of the alloy elements to prepare an alloy mixture of the components, carrying out vacuum melting on the alloy mixture, atomizing the alloy mixture by using high-purity nitrogen to prepare powder, wherein the nitrogen content of the powder is 0.11 percent, the oxygen content of the powder is 0.045 percent, and sieving the powder with the granularity of 50-180 mu m to prepare the B-C-N-O supersaturated solid solution austenitic stainless steel powder which is used for producing the B-C-N-O atomic solid solution strengthening and toughening effect by laser forming.

Step S3, as shown in FIG. 1, the prepared B-C-N-O supersaturated solid solution austenitic stainless steel powder is clad in a laser melting bath by adopting a rapid cooling induction non-equilibrium phase change cladding method, a circulating water cooling air curtain cover is used for protecting a laser synchronous lateral powder feeding nozzle device, a base material subjected to sand blasting treatment is placed on a circulating water cooling device, then a laser scanning track is determined by controlling an experimental worktable, the distance between a nozzle of a laser and the base material is adjusted, and the laser forming high-performance austenitic stainless steel powder is clad on the surface of the base material by adopting a lateral synchronous powder feeding method, so that the austenitic stainless steel laser cladding layer with high strength and excellent plasticity and corrosion resistance can be prepared, wherein the laser energy density is 480W/mm²The scanning speed is 9mm/s, the powder feeding speed is 5g/min, the lapping coefficient is 0.5, and the protective gas is high-purity nitrogen.

Example 5

Step S1, the supersaturated solid-solution austenitic stainless steel powder of B-C-N-O comprises the following elements in percentage by mass: 0.32 percent of C, 16.5 percent of Cr, 7 percent of Ni, 0.001 percent of B, 0.70 percent of Si, 0.08 percent of N, 0.05 percent of O and the balance of Fe, wherein the sum of the mass percentages is 100 percent;

and S2, selecting intermediate transition alloys of iron carbon, iron chromium, iron silicon, ferroboron and pure nickel according to the mass percent of the alloy elements to prepare an alloy mixture of the components, carrying out vacuum melting on the alloy mixture, atomizing the alloy mixture by using high-purity nitrogen to prepare powder, wherein the nitrogen content and the oxygen content of the powder are respectively 0.08% and 0.05%, and sieving the powder with the granularity of 50-180 mu m to prepare the B-C-N-O supersaturated solid solution austenitic stainless steel powder which is used for laser forming to generate the B-C-N-O atomic solid solution strengthening and toughening effect.

Step S3, as shown in FIG. 1, the prepared B-C-N-O supersaturated solid solution austenitic stainless steel powder is clad in a laser molten pool by adopting a rapid cooling induced non-equilibrium phase change cladding method, a laser synchronous lateral powder feeding nozzle device is protected by a circulating water cooling type air curtain cover, and a base material treated by sand blasting is subjected toPlacing on a circulating water cooling device, determining laser scanning track by controlling an experimental worktable, adjusting the distance between a nozzle of a laser and a substrate, cladding laser-formed high-performance austenitic stainless steel powder on the surface of the substrate by adopting a lateral synchronous powder feeding method, and thus obtaining the austenitic stainless steel laser cladding layer with high strength, excellent plasticity and corrosion resistance, wherein the laser energy density is 300W/mm²The scanning speed is 5mm/s, the powder feeding speed is 2g/min, the lapping coefficient is 0.5, and the protective gas is high-purity nitrogen.

Example 6

Step S1, the supersaturated solid-solution austenitic stainless steel powder of B-C-N-O comprises the following elements in percentage by mass: 0.6 percent of C, 21.3 percent of Cr, 10 percent of Ni, 0.008 percent of B, 0.11 percent of Si, 0.10 percent of N, 0.06 percent of O and the balance of Fe, wherein the sum of the mass percentages is 100 percent;

and step S2, selecting intermediate transition alloys of iron carbon, iron chromium, iron silicon, ferroboron and pure nickel according to the mass percent of the alloy elements to prepare an alloy mixture of the components, carrying out vacuum melting on the alloy mixture, atomizing the alloy mixture by using high-purity nitrogen to prepare powder, wherein the nitrogen content and the oxygen content of the powder are respectively 0.10% and 0.06%, and sieving the powder with the granularity of 50-180 mu m to prepare the B-C-N-O supersaturated solid solution austenitic stainless steel powder which is used for laser forming to generate the B-C-N-O atomic solid solution strengthening and toughening effect.

Step S3, as shown in FIG. 1, the prepared B-C-N-O supersaturated solid solution austenitic stainless steel powder is clad in a laser melting bath by adopting a rapid cooling induction non-equilibrium phase change cladding method, a circulating water cooling air curtain cover is used for protecting a laser synchronous lateral powder feeding nozzle device, a base material subjected to sand blasting treatment is placed on a circulating water cooling device, then a laser scanning track is determined by controlling an experimental worktable, the distance between a nozzle of a laser and the base material is adjusted, and the laser forming high-performance austenitic stainless steel powder is clad on the surface of the base material by adopting a lateral synchronous powder feeding method, so that the austenitic stainless steel laser cladding layer with high strength and excellent plasticity and corrosion resistance can be prepared, wherein the laser energy density is 500W/mm²At a scanning speed of10mm/s, the powder feeding speed is 7g/min, the lap joint coefficient is 0.5, and the protective gas is high-purity nitrogen.

As shown in FIG. 12, in the comparative graphs of stress/strain curves of examples 1 to 6, the tensile strength of the formed layer sample prepared by laser forming in examples 1 to 4 in the six groups (nitrogen content can reach 0.11 to 0.13%, carbon content can reach 0.38 to 0.47%, and oxygen content is controlled to be 0.050 to 0.060%) reaches 961 + -40 MPa, the yield strength reaches 671 + -20 MPa, and the elongation reaches 37.5 + -3%, wherein example 4 is the most stable within the range, and the fluctuation of the mechanical properties is small in multiple measurements, and example 5 has a low C content, a tensile strength of 676 + -20 MPa, a yield strength of 590 + -15 MPa, and an elongation of 36 + -3%. Compared with the first four groups, the mechanical property of the example 5 is poor, and the industrial application advantage is lacked; example 6 the too high C, Si content, the tensile strength of 984 + -20 MPa, the yield strength of 788 + -40 MPa, the too low elongation of 14.5 + -3%, lost the toughness of austenitic stainless steel and increased Cr, Ni content further aggravated the production cost investment, also lacked the industrial utility value.

Table 1 examples 1-6 tensile test mechanical parameters

Examples	Tensile strength (MPa)	Yield strength (MPa)	Elongation (%)
				Examples 1 to 4	961±40	671±20	37.5±3
Example 5	676±20	590±15	36.0±3
				Example 6	984±20	788±40	14.5±3

In order to illustrate the rationality of the above-mentioned ingredients and the innovativeness of the present invention, the present invention makes the following theoretical analysis and experimental verification by combining the modern test technology with the embodiment 4 (the following detection phenomena occur in the embodiments 1 to 4):

as shown in fig. 2a-d, which are the metallographic images of the cladding layer sample after 300 ℃ x 2h air cooling, 500 ℃ x 2h air cooling and 700 ℃ x 2h air cooling, respectively, the metallographic images are fine polygonal crystal grains with straight grain boundaries and obvious austenite micro-metallographic characteristics; to further determine the phase and microstructure, the cladding layer was analyzed using XRD, SEM, TEM and EPMA: as can be seen from the XRD spectrogram of fig. 3, the phase structures of the cladding layer sample, the sample after air cooling at 300℃ × 2h and 500℃ × 2h are all austenite, and the sample after air cooling at 700℃ × 2h mainly consists of austenite and ferrite; the distribution data of the 3DAP three-dimensional atom probe is calculated according to the statistical principle, and the dispersion coefficients of the concentrations of Si (reference atoms) and C atoms are respectively as follows: 1.5562, 2.1074; the comparison shows that the fluctuation of the C atom concentration is larger than that of Si atoms, and the 3DAP three-dimensional atom probe distribution diagram in figure 4 further shows that part of two C-O interstitial atoms in the sample are subjected to short-range migration after air cooling at 300 ℃ for 2h, obvious C-O interstitial atom agglomeration is formed on the scale of 1nm (N element is not marked because the atom probe cannot distinguish N and Si elements), and the element distribution is more uniform in air cooling at 500 ℃ for 2h of the cladding layer as shown in figure 5a and no interface segregation is seen through the analysis of an energy spectrometer (EDS); as shown in FIGS. 5b-d (FIG. 5, c is the position of EDS line scanning at low magnification, b, d are the fluctuation of each element content of line scanning surface at different positions at high magnification, hereB and d are taken as two times to repeatedly verify whether a precipitated phase exists on the grain boundary) to obtain that: a straight line is arbitrarily selected from a 500 ℃ multiplied by 2h air cooling sample of a cladding layer sample, the content of Cr, Fe, Ni and Si elements at each grain boundary on the straight line tends to be stable, no obvious fluctuation exists, namely no obvious grain boundary chromium-poor area appears, and the results show that a great amount of carbon and nitrogen atoms are trapped and fixed in austenite without obvious grain boundary segregation and M₂₃C₆Separating out a phase; FIGS. 6a, b, c and d are grain boundary morphologies of TEM bright field image grains (grain boundaries at four positions a, b, c and d are arbitrarily taken) of the cladding layer sample at different positions, and are used for explaining that the grain boundaries all present clear morphologies and have no obvious precipitated phases; as is clear from the TEM bright field image of FIG. 6 and the TEM diffraction spots of FIG. 7, the crystal grains and the vicinity of the grain boundaries in the cladding layer sample had a face-centered crystal structure, and M was not observed₂₃C₆A phase precipitated. FIG. 7a shows the diffraction spot at macroscopic magnification, FIG. 7b shows the diffraction spot in the (1, 1, 0) direction, FIG. 7c shows the two larger diffraction spots in the (1, 1, 0) direction, and FIG. 7d shows the smaller diffraction spot in the (1, 1, 0) direction; FIG. 7abcd is a scale of different diffraction spots illustrating that the cladding samples all have austenite phases with Face Centered Cubic (FCC) structure, with the larger and smaller comparison referring to the diffraction spot of FIG. 7 b.

As can be seen from the stress-strain curves of the cladding layer sample, the sample after 300 ℃x2 h air cooling, 500 ℃x2 h air cooling, and 700 ℃x02 h air cooling, and the AISI304 sample, as shown in fig. 8, the tensile strength of the cladding layer sample, the sample after 300 ℃x2 h air cooling, and 500 ℃x2 h air cooling is about 1.5 times that of the AISI304, the yield strength is about 1.4 times that of the AISI304, and the elongation thereof is close to that of the AISI304 while maintaining relatively stable mechanical properties, all of which are about 37%. 5 ± 3; and after the air cooling at 700 ℃ for 2h, the mechanical property of the sample is higher, but the elongation of the sample is reduced sharply. Referring to fig. 9a-d, fracture surfaces of the cladding layer samples after 300 ℃ x 2h air cooling and 500 ℃ x 2h air cooling show a large number of uniform equiaxial dimples (circular micro pits uniformly distributed on fracture surface), the depth of the dimple is obviously deeper than that of the fracture surface after 700 ℃ x 2h air cooling, and the fracture surface after 700 ℃ x 2h air cooling only has a small number of shallow dimples, as shown by the quantitative analysis of XRD spectrum in fig. 3, the cladding layer structure after 700 ℃ x 2h air cooling does not have interstitial precipitated phase, but 12.8% of ferrite phase is generated and 900 ℃ is generated28.9 percent of ferrite phase and 7.8 percent of M in the cladding layer structure after 2 hours of air cooling₂₃C₆The elongation is reduced rapidly due to phase precipitation, the phase structure of the sample is still 100% austenite phase after the air cooling treatment within 500 ℃ for 2h, B-C-N-O interstitial atoms are not precipitated, and the room-temperature mechanical property of the cladding layer is not changed obviously after the heat treatment within the temperature range.

TABLE 2 tensile specimen mechanical Property parameters

Electrochemical corrosion cathode polarization curves of the cladding layer sample, the sample after 300 ℃ x 2h air cooling, 500 ℃ x 2h air cooling, 700 ℃ x 2h air cooling and the AISI304 sample can be seen in fig. 10, the self corrosion potentials of the cladding layer sample, the sample after 300 ℃ x 2h air cooling and 500 ℃ x 2h air cooling are slightly reduced but are all higher than AISI304, the sample after 700 ℃ x 2h air cooling is obviously lower than AISI304, the corrosion current density and the corrosion rate are far higher than the former three, and the quantitative analysis of an XRD spectrogram combined with a chart in fig. 3 shows that after 700 ℃ x 2h air cooling, the cladding layer tissue does not generate obvious interstitial atom precipitated phase, but 12.8% of ferrite phase generates, so that the corrosion resistance is sharply reduced and is worse than AISI304, the cladding layer sample after 500 ℃ x 2h air cooling treatment is still 100% of austenite phase, the corrosion resistance is stable and better than AISI304, and the B-C-N-O interstitial atoms are not polymerized in the cladding layer, and are also not brittle and not polymerized in the cladding layer A supersaturated solid solution form exists in which the ceramic phase is transformed. FIG. 11 shows the short-range order detection result of synchrotron radiation, which further illustrates the existence of short-range order structure in B-C-N-O interstitial atoms. The octahedral gap position k is shown in FIG. 13, the gap radius is

It is assumed that at the k position C,

the distance between 1-2 atoms becomes:

and (4) conclusion: if one carbon C is dissolved in the octahedral interstitial sites in the austenite cells, the distance between 1 and 2 atoms becomes

Approximate synchrotron radiation experimental correspondence value of FIG. 11

Further, the other three interstitial atom synchrotron radiation short-range ordered detection results show that B-C-N-O interstitial atoms have short-range ordered structures.

TABLE 3 electrochemical Corrosion Performance parameters of the samples

In conclusion, the laser cladding layer prepared by laser forming the B-C-N-O atom solid solution toughened high-performance austenitic stainless steel powder (the tensile strength reaches 961 +/-40 MPa, the yield strength reaches 671 +/-20 MPa and the elongation reaches 37.5 +/-3 percent) has the tensile strength and the yield strength which are 1.4-1.5 times of those of AISI304, and the ductility and the toughness which are equivalent to those of the AISI304 are 37.5 +/-3 percent; no B-C-N-O interstitial atom precipitated phase appears after the air cooling treatment within 500 ℃ for 2h, the room-temperature mechanical property of the sample does not obviously change after the heat treatment, and the corrosion resistance is slightly reduced but still higher than AISI304 compared with the original laser forming property. The above results all show that B-C-N-O interstitial atoms are relatively stable supersaturated and dissolved in austenite due to the existence of short-range ordered combination, so that the formation of an interface chromium-poor region is avoided and an obvious interstitial atom strengthening and toughening effect is generated.

The above description is only an embodiment of the method of the present invention, and other embodiments can be described in the same manner as above, and the same and similar parts between the embodiments can be referred to each other. For the system embodiment, since it is basically similar to the method embodiment, it can be described simply, and the relevant points can be referred to the partial description of the method embodiment. The above embodiments of the method are preferred embodiments, and are not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims

1. A supersaturated solid-solution austenitic stainless steel powder of B-C-N-O, characterized in that,

the material consists of the following elements in percentage by mass: 0.40-0.48% of C, 18.5-19.0% of Cr, 8.0-9.0% of Ni, 0.001-0.006% of B, 0.80-0.95% of Si, 0.08-0.12% of N, 0.045-0.055% of O and the balance of Fe, wherein the sum of the mass percentages is 100%;

the powder is prepared by vacuum melting of intermediate transition alloy containing corresponding elements and high-purity nitrogen atomization, and is used for obtaining B-C-N-O interstitial atom supersaturated solid-solution austenitic stainless steel by rapid cooling forming of a laser melting pool under the protection of high-purity nitrogen in an atmospheric environment.

2. A supersaturated solid solution austenitic stainless steel powder according to claim 1, wherein the powder consists of, in mass%: 0.46 percent of C, 18.71 percent of Cr, 8.37 percent of Ni, 0.001 percent of B, 0.85 percent of Si, 0.11 percent of N, 0.045 percent of O and the balance of Fe, wherein the sum of the mass percentages is 100 percent.

3. The method for preparing B-C-N-O supersaturated solid solution austenitic stainless steel powder as claimed in claim 1, wherein according to the mass percentage of each element of the powder, selecting intermediate transition alloy iron carbon, iron chromium, iron silicon, ferroboron and pure nickel, preparing alloy mixture with required proportion components, vacuum melting the alloy mixture, atomizing the alloy mixture with high purity nitrogen gas to prepare powder, wherein the nitrogen content of the powder is 0.08-0.12%, the oxygen content is 0.045-0.055%, and sieving the powder with the granularity of 50-180 μm to obtain the B-C-N-O supersaturated solid solution austenitic stainless steel powder.

4. A method for the production of a supersaturated solid solution austenitic stainless steel powder of B-C-N-O according to claim 3, characterized in that the powder consists of the following elements, in mass%: 0.46% of C, 18.71% of Cr, 8.37% of Ni, 0.001% of B, 0.85% of Si, 0.11% of N, 0.045% of O and the balance of Fe, wherein the sum of the mass percentages is 100%.

5. The method for cladding the B-C-N-O supersaturated solid solution austenitic stainless steel powder as claimed in claim 3, wherein the method comprises the steps of performing rapid cooling induction on the B-C-N-O supersaturated solid solution austenitic stainless steel powder in a laser molten pool to perform unbalanced phase transformation, protecting a laser synchronous lateral powder feeding nozzle device by using a circulating water cooling type air curtain shield, placing the base material subjected to sand blasting treatment on a circulating water cooling device, determining a laser scanning track by controlling an experimental worktable, adjusting the distance between a nozzle of a laser and the base material, and cladding the laser formed high-performance austenitic stainless steel powder on the surface of the base material by using a lateral synchronous powder feeding method, so that the austenitic stainless steel laser cladding layer with high strength, excellent plasticity and corrosion resistance can be prepared.

6. The cladding method of B-C-N-O supersaturated solid solution austenitic stainless steel powder according to claim 5, characterized in that, the laser treatment process conditions are as follows: laser energy density of 300-500W/mm²The scanning speed is 6-9 mm/s, the powder feeding speed is 3-5 g/min, the lapping coefficient is 0.5, and the protective gas is high-purity nitrogen.