CN114472921A

CN114472921A - Method for preheating non-contact ultrasonic-assisted direct laser deposition metal material

Info

Publication number: CN114472921A
Application number: CN202210031702.0A
Authority: CN
Inventors: 陈岁元; 周林; 马明志; 贾无名; 崔彤; 汪芦婷
Original assignee: Northeastern University China
Current assignee: Northeastern University China
Priority date: 2022-01-12
Filing date: 2022-01-12
Publication date: 2022-05-13
Anticipated expiration: 2042-01-12
Also published as: CN114472921B

Abstract

The invention provides a method for preheating a non-contact ultrasonic-assisted direct laser deposition metal material, which comprises the steps of arranging an ultrasonic generator in a machine cabin of a laser additive manufacturing device, wherein the output end of the ultrasonic generator is not in contact with a substrate and a deposition layer; assembling a preheating substrate device at the bottom of the base plate, and preheating the base plate by the preheating substrate device; the laser additive manufacturing device carries out laser deposition, the ultrasonic generator transmits ultrasonic waves to the molten pool in the laser deposition process, and the substrate preheating device continuously preheats. The method can introduce ultrasonic waves into a molten pool by taking air as a medium under the conditions of not contacting a substrate and not damaging the surface of a deposition sample in the whole deposition process, and simultaneously has a double synergistic action mechanism of a temperature field and a stress field, so that the prepared alloy steel material has the characteristics of fewer defects and better structural property, toughness and matching, and can meet the requirements of shape control and controllability application technologies of direct laser deposition of high-performance metal parts.

Description

Method for preheating non-contact ultrasonic-assisted direct laser deposition metal material

Technical Field

The invention relates to the technical field of laser material increase, in particular to a method for preheating a non-contact ultrasonic-assisted direct laser deposition metal material.

Background

In recent years, direct laser deposition has been widely used in large parts of complexity and high performance as one of short-run manufacturing techniques due to its unique processing method. However, some defects such as air holes, cracks, inclusions, etc. are generated in the direct laser deposition process. The presence of these defects will significantly reduce the compactness of the material and seriously affect the performance of the part. Therefore, it is necessary to take certain measures to control and reduce defects in the sample during deposition. And introduction of external physical field treatment to influence the solidification behavior of the laser molten pool and control the tissue properties thereof has become a hot point of research. Therefore, how to introduce an external physical field by using a unique forming method of a direct laser deposition process to finally achieve the purpose of adjusting defects, tissues and properties in a molten pool has great scientific significance and practical application value.

Direct laser deposition is a fast-heating and fast-cooling process, each area where laser passes through can be subjected to fast melting and fast cooling processes, complex tensile stress and compressive stress can be generated in the areas due to melting, thermal expansion, cooling, temperature reduction and contraction, and the maximum tensile stress exceeds the maximum strength borne by a material due to uneven stress distribution of each area in a sample, so that the sample is cracked. In addition, some metallurgical reactions are accompanied when the metal powder is irradiated by laser and melted in the deposition process, and bubbles in a laser molten pool are generated due to the protective gas in the deposition process, the bubbles do not escape from the molten pool after the molten pool is solidified, and finally, pores are formed and remained in the sample. Meanwhile, the direct laser deposition alloying process is a typical non-equilibrium metallurgical process, and the structure phase change, the grain size, the number of phases and the like of the direct laser deposition alloying process are different due to the change of a temperature field and a stress field in a molten pool, so how to scientifically carry out purposeful influence on the solidification process of a laser molten pool by adding an external field factor to promote the formation of an alloy material with few crack and pore defects, refined structure and different types and numbers of phases, realize the regulation and control of the matching of formed structure and performance toughness, and become a serious scientific research work.

Aiming at the characteristics of the generation of crack and air hole defects of the deposited metal material by a temperature field in the deposition process and the regulation and control of alloy steel structure, the introduction of preheating can effectively reduce the temperature gradient between the base material and the deposited layer, further reduce the residual stress of the deposited layer, achieve the purpose of slowing down the crack initiation, and simultaneously preheat the solidification speed of the molten pool, thereby being beneficial to air hole precipitation and regulation and control of the structure. The introduction of the ultrasonic wave can effectively refine grains and regulate and control the stress distribution among settled layers, and the flow state of the molten pool is changed due to the introduction of the ultrasonic wave into the molten pool, so that the effect of regulating and controlling pores and tissues is achieved.

Domestic and foreign researches show that independent preheating and ultrasonic application have obvious effects of regulating and controlling tissues and defects and have already been well applied in engineering practice. Most of the introduced ultrasonic vibration modes are base plate bottom vibration and settled layer surface impact vibration, but the ultrasonic vibration modes cannot be used for manufacturing and remanufacturing large and complex metal parts such as high-speed rail brake discs, nuclear power emergency diesel shafts, rolling mills and the like, and the problems that auxiliary equipment is difficult to apply and the parts face damage exist. Therefore, the development of the non-contact ultrasonic auxiliary process which does not damage parts and effectively introduces ultrasonic waves has more convenient application prospect. Meanwhile, how to introduce two physical fields of preheating and non-contact ultrasound into the process of directly depositing the metal material by laser is a new scientific problem of double-field synergistic coupling effect and a new method for researching and developing defects and tissue properties in the deposited metal material with high efficiency. Therefore, it is necessary to research two external field composite assisted direct laser deposition to regulate and control the solidification behavior of a laser melting pool, establish a double-field synergistic action mechanism, solve the problem that crack and pore defects are easy to occur in the process of directly depositing metal parts by laser and the problem that the structural performance and toughness are poor in matching, obtain an advanced double-field synergistic assisted laser direct deposition technology of high-performance alloy steel parts, and lay a theoretical and technical foundation for the industrial application of the direct laser deposition technology.

Disclosure of Invention

According to the problems, the invention provides a method for directly depositing a metal material by laser with preheating-non-contact ultrasonic composite assistance, and the invention principle is that based on the change requirements of a temperature field and stress field double-field synergistic mechanism and an ultrasonic assistance mode, the unbalanced metallurgical solidification process of a laser molten pool is influenced, the pore crack defect is eliminated, the crystal grain is refined, the structure performance is regulated and controlled, and finally, the high-quality metal material with the defect-free structure performance and the obdurability matching is obtained. The problem of overlarge temperature gradient between the substrate and the deposition layer is solved by preheating the substrate; the ultrasonic wave of the bracket is introduced into the molten pool through an air medium in a mode of not contacting the substrate and the sedimentary layer, so that the problems that the ultrasonic device cannot be assembled on a large part and the defect of the inside of the part is overcome; through the composite design of the two external field devices, preheating and non-contact ultrasonic treatment are simultaneously introduced into the process of direct laser deposition of metal materials, so that a double-field auxiliary direct laser deposition process system is formed. Through the parameter research of two processes of preheating and non-contact ultrasonic, the influence rule of the composite process technology on defect elimination and the matching of the tissue performance and toughness is clarified, and a double-field cooperative regulation and control action mechanism is established; the new method for directly depositing the high-performance metal material by laser assisted by preheating-non-contact ultrasonic compounding is obtained.

The technical means adopted by the invention are as follows:

a method of preheating a non-contact, ultrasonically assisted, direct laser deposition metallic material, comprising:

arranging an ultrasonic generator in a cabin of the laser additive manufacturing device, wherein the output end of the ultrasonic generator is not in contact with the substrate and the deposition layer, an included angle alpha is formed between the axis of the output end of the ultrasonic generator and the substrate, the axis of the output end of the ultrasonic generator is intersected with the axis of the laser output end of the laser additive manufacturing device, and the intersection point is positioned in a molten pool on the substrate;

cleaning the surface of the substrate to be processed to ensure that the surface is bright and has no oxide skin;

placing a substrate preheating device on a working table top of a laser additive manufacturing device, wherein the substrate preheating device is positioned at the bottom of a base plate and preheats the base plate;

corresponding laser process parameters are set on a control panel of the laser additive manufacturing device in advance, and an infrared temperature measuring device is adopted to monitor the temperature of the substrate in real time. When the temperature of the substrate reaches the required temperature, the laser additive manufacturing device carries out laser deposition, the ultrasonic generator transmits ultrasonic waves to the molten pool through an air medium in the laser deposition process, and the substrate preheating device continuously preheats.

The method comprises the steps of preheating a substrate at different temperatures by using a substrate preheating device based on optimal process parameters and optimized laser process parameters of a single non-contact ultrasonic field by using a controlled variable method, and printing samples with different ultrasonic parameters according to a designed scanning path by using a direct laser deposition process.

And after the laser deposition is finished, closing the laser additive manufacturing device, the substrate preheating device and the ultrasonic generator.

Preferably, α is 30-60 °.

Preferably, the power of the ultrasonic generator is 120-600W.

Preferably, the preheating temperature of the preheating substrate device is 50-200 ℃.

Preferably, the ultrasonic generator is suspended above the substrate by a bracket, and the bracket is used for fixing the ultrasonic emitter and adjusting an included angle alpha between the ultrasonic generator and the substrate.

Compared with the prior art, the invention has the following advantages:

the preheating-non-contact ultrasonic composite auxiliary method can introduce ultrasonic waves into a molten pool by taking air as a medium under the conditions of not contacting a substrate and not damaging the surface of a deposition sample in the whole deposition process, and has the advantage of solving the technical problem that the traditional ultrasonic vibration mode cannot be equipped for manufacturing large parts. In addition, the process method for simultaneously and effectively introducing preheating and non-contact ultrasonic also has a temperature field and stress field dual synergistic action mechanism, so that the prepared metal material has the characteristics of fewer defects and better structural property, toughness and matching, and can meet the requirements of shape control and property control application technologies of direct laser deposition high-performance metal parts.

For the reasons, the laser additive manufacturing method can be widely popularized in the fields of laser additive manufacturing and the like.

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 introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a schematic diagram of an apparatus used in a method for preheating a non-contact ultrasonic-assisted direct laser deposition metal material in embodiments 1 to 3 of the present invention.

Fig. 2 is a macroscopic metallographic representation of a 24CrNiMoY alloy steel sample prepared in inventive example 1.

Fig. 3 is a scanned texture map of a 24CrNiMoY steel sample prepared in inventive example 1.

Fig. 4 is an XRD diffractogram of a 24CrNiMoY alloy steel sample prepared in inventive example 1.

Fig. 5 is an EBSD analysis chart of a 24CrNiMoY alloy steel sample prepared in inventive example 1.

Fig. 6 is a graph of hardness data for 24CrNiMoY steel samples prepared in inventive example 1.

Fig. 7 is a wear schematic diagram of a 24CrNiMoY steel sample prepared in example 1 of the present invention, in which (a) is a low-magnification wear scar morphology, and (b) is an enlarged morphology of a middle region in (a).

Fig. 8 is a graph of the room temperature tensile profile of a 24CrNiMoY steel sample prepared in inventive example 1.

Fig. 9 is a macroscopic metallographic representation of a 24CrNiMoY alloy steel sample prepared in inventive example 2.

FIG. 10 is a texture mapping of a 24CrNiMoY alloy steel sample prepared in inventive example 2.

Fig. 11 is an XRD diffractogram of the 24CrNiMoY alloy steel sample prepared in inventive example 2.

Fig. 12 is an EBSD analysis chart of a 24CrNiMoY alloy steel sample prepared in inventive example 2.

Fig. 13 is a graph of hardness data for 24CrNiMoY steel samples prepared in inventive example 2.

Fig. 14 is a wear schematic diagram of a 24CrNiMoY steel sample prepared in example 2 of the present invention, in which (a) is a low-magnification wear scar morphology, and (b) is an enlarged morphology of a middle region in (a).

Fig. 15 is a graph of the room temperature tensile profile of a 24CrNiMoY steel sample prepared in inventive example 2.

Fig. 16 is a macroscopic metallographic representation of a 24CrNiMoY steel sample prepared in inventive example 3.

Fig. 17 is a scanned texture map of a 24CrNiMoY steel sample prepared in inventive example 3.

Fig. 18 is an XRD diffractogram of the 24CrNiMoY alloy steel sample prepared in inventive example 3.

Fig. 19 is an EBSD analysis chart of a 24CrNiMoY alloy steel sample prepared in inventive example 3.

Fig. 20 is a graph of hardness data for 24CrNiMoY steel samples prepared in inventive example 3.

Fig. 21 is a wear schematic diagram of a 24CrNiMoY steel sample prepared in example 3 of the present invention, in which (a) is a low-magnification wear scar morphology, and (b) is an enlarged morphology of a middle region in (a).

Fig. 22 is a graph of the room temperature tensile profile of a 24CrNiMoY steel sample prepared in inventive example 3.

Detailed Description

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, 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. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. 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.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

The relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. Any specific values in all examples shown and discussed herein are to be construed as exemplary only and not as limiting. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.

In the description of the present invention, it is to be understood that the orientation or positional relationship indicated by the directional terms such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal" and "top, bottom", etc., are generally based on the orientation or positional relationship shown in the drawings, and are used for convenience of description and simplicity of description only, and in the absence of any contrary indication, these directional terms are not intended to indicate and imply that the device or element so referred to must have a particular orientation or be constructed and operated in a particular orientation, and therefore should not be considered as limiting the scope of the present invention: the terms "inner and outer" refer to the inner and outer relative to the profile of the respective component itself.

Spatially relative terms, such as "above … …," "above … …," "above … … surface," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial relationship to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, devices described as "above" or "on" other devices or configurations would then be oriented "below" or "under" the other devices or configurations. Thus, the exemplary term "above … …" can include both an orientation of "above … …" and "below … …". The device may be otherwise variously oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

It should be noted that the terms "first", "second", and the like are used to define the components, and are only used for convenience of distinguishing the corresponding components, and the terms have no special meanings unless otherwise stated, and therefore, the scope of the present invention should not be construed as being limited.

Example 1

As shown in fig. 1 to 8, a method for preheating a non-contact ultrasonic-assisted direct laser deposition metal material includes:

1. ultrasonic generator 2 (its model is JZ3000) is suspended in the machine storehouse of laser vibration material disk manufacturing device through support 1, adjusts support 1 and makes ultrasonic generator 2 personally submit 60 with base plate 3 level. Continuing to adjust the bracket 1 to enable the axis of the output end of the ultrasonic generator 2 to intersect with the axis of the laser output end 4 (the model is FL-Dlight02-3000W) of the laser additive manufacturing device, and enabling the intersection point to be located in a molten pool on the substrate 3 (the material of the substrate is Q235); and the output end of the ultrasonic generator 2 is 2cm away from the red light mark on the substrate 3 (the mark emitted from the laser output end 3 to the substrate 3).

2. The ultrasonic generator 2 is connected with the ultrasonic control panel 5 of the ultrasonic generator 2, and the ultrasonic power bandwidth is set to be 60% on the ultrasonic control panel 5, namely, the output ultrasonic power is 360W at the moment, and the amplitude is 21 μm.

3. Laser process parameters (laser energy density 83.3J/mm) are adjusted on a laser control panel 6 of a laser output end 4²) And the lapping rate is 40 percent and other laser process parameters. The defocusing amount of the laser output end 4 is adjusted to 304 mm.

4. A substrate preheating device 7 (model number DB-XAB) was placed at the bottom of the base plate 3, and the preheating temperature of the substrate preheating device 7 was set to 50 ℃.

5. And (3) measuring the temperature of the substrate 3 in real time by using a DT1310 table, clicking the 'Run' of the ultrasonic control panel 5 and the 'automatic-start' of the laser control panel 6 when the temperature of the substrate 3 reaches 50 ℃, and starting preheating-non-contact ultrasonic composite assisted direct laser deposition of the alloy steel sample. In the laser additive process, 24CrNiMoY alloy steel is used as a powder feeding raw material, a 24CrNiMoY alloy steel sample is prepared in a snakelike scanning mode, and Ar is used as protective gas.

6. After the printing of the multilayer multi-channel sample is finished, the stop button of the ultrasonic control panel 5, the stop button of the laser control panel 6 and the substrate preheating device 7 are clicked.

And cutting a sample with a required size by adopting an electric spark cutting machine, and performing organization and performance characterization on the sample. The following analytical tests were performed on the direct laser deposited 24CrNiMoY steel samples prepared in this example:

(1) metallographic phase and density analysis of 24CrNiMoY alloy steel sample in example 1:

the alloy steel samples prepared in this example were subjected to a macroscopic metallographic analysis as shown in fig. 2. The alloy steel samples, which had good layer-to-layer bonding and no large unfused gap observed, had a density of 99.63% as measured by archimedes drainage, due to the introduction of ultrasound and the application of preheating, while assisting in the escape of bubbles within the bath with synergistic assistance and thus achieving good density.

(2) Scanning texture analysis of 24CrNiMoY alloy steel samples in example 1:

FIG. 3 shows SEM morphology of a preheated-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, which mainly consists of upper bainite and lower bainite structures. It is clear that the short rod-like theta-cementite is aligned in parallel along the direction of the Bainitic Ferrite (BF) principal axis, which is characteristic of the typical upper bainite. The mixed bainite structure has better strong hardness.

(3) XRD diffraction analysis of 24CrNiMoY alloy steel sample in example 1:

FIG. 4 is an X-ray diffraction pattern of a preheating-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, and the main phase of the 24CrNiMoY alloy steel sample is an alpha-Fe solid solution phase.

(5) EBSD analysis of 24CrNiMoY alloy steel samples in example 1:

FIG. 5 is an EBSD data analysis of a pre-heat-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample. The statistics of the grain boundaries with large and small angles shows that the proportion of the large angle grain boundaries is 47.2 percent, the proportion of the small angle grain boundaries is 52.8 percent, the proportion of <111> twin grain boundaries is 13.5 percent, and the size of the original austenite grain boundaries is 2.5 mu m.

(6) Hardness data analysis of 24CrNiMoY alloy steel samples in example 1:

FIG. 6 is a microhardness distribution diagram of a preheating-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, and the average microhardness of the sample is 366.4 +/-39 HV_0.2。

(7) Wear data analysis of 24CrNiMoY alloy steel samples in example 1:

FIG. 7 shows the wear scar morphology of a preheated-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, and the wear of the wear sample is 1.4mg by weighing the wear sample before and after the wear sample.

(8) Tensile data analysis of 24CrNiMoY alloy steel samples in example 1:

FIG. 8 is the room temperature tensile curve of the 24CrNiMoY alloy steel sample in this example, the tensile strength of the direct laser deposited alloy steel reaches 1026MPa, and the average elongation is 12.3%.

Example 2

As shown in fig. 1 and 9 to 15, the present embodiment is different from embodiment 1 in that the preheating temperature of the substrate preheating device 7 is 100 ℃.

And cutting a sample with a required size by using an electric spark cutting machine, and performing organization and performance characterization on the sample. The following analytical tests were performed on the direct laser deposited 24CrNiMoY steel samples prepared in this example:

(1) metallographic phase and density analysis of 24CrNiMoY alloy steel sample in example 2:

the alloy steel samples prepared in this example were subjected to a macroscopic metallographic analysis as shown in fig. 9. No gaps were observed between the layers of the alloy steel sample, which had a density of 99.83% as measured by Archimedes drainage. Compared with the embodiment 1, the density of the sample of the present example is obviously increased, which shows that under the parameters of the example, the escape of bubbles is accelerated by the ultrasonic waves and the preheating temperature in the molten pool, and the sample with high density is obtained.

(2) Scanning texture analysis of 24CrNiMoY alloy steel sample in example 2:

FIG. 10 shows SEM morphology of preheated-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel samples, which mainly consists of upper bainite, lower bainite and GB2 granular bainite structures. And a plurality of fine precipitated carbides appear among the bainitic ferrite lath bundles, and the carbides distributed by the precipitates and the growth direction of the BF lath bundles are 50-80 degrees, which is a typical characteristic of a lower bainite structure. In addition, a less massive bainitic ferrite matrix and island-like structures with short rods growing along the laths were observed, which is the morphology of GB2 granular bainite. The presence of granular bainite in the structure at this time is due to the increase in the preheating temperature, and satisfies the forming environment of granular bainite of GB2 type. The mixed bainite structure has better toughness matching.

(3) XRD diffraction analysis of 24CrNiMoY alloy steel sample in example 2:

FIG. 11 is an X-ray diffraction pattern of a preheating-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, and main phases of the 24CrNiMoY alloy steel sample are an alpha-Fe solid solution phase and a gamma-Fe phase.

(4) EBSD analysis of 24CrNiMoY alloy steel samples in example 2:

FIG. 12 is an EBSD data analysis of pre-heat-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel samples. The statistics of the large and small angle grain boundaries are carried out, the proportion of the large angle grain boundaries is 57.0 percent, the proportion of the small angle grain boundaries is 43.0 percent, the proportion of <111> twin grain boundaries is 26.3 percent, and the size of the prior austenite grain boundaries is 0.9 mu m. At this time, the grain size is refined and the small angle grain boundaries are reduced compared to the data of example 1, which are attributed to the increase of the preheating temperature, causing a change in the tissue transformation process in the molten pool.

(5) Hardness data analysis of 24CrNiMoY alloy steel samples in example 2:

FIG. 13 is a microhardness distribution diagram of a preheating-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, and the average microhardness of the sample is 390.6 +/-54 HV_0.2. The increase in hardness values is due to the refinement of the grain size of the samples at this time.

(6) Wear data analysis of 24CrNiMoY alloy steel samples in example 2:

FIG. 14 shows the wear scar morphology of a preheated-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, and it is observed that the pear furrows in the wear scar morphology of the alloy steel sample in the embodiment 2 are shallow, and only a few particles are peeled off. The abraded sample was weighed before and after the abrasion, and the abrasion was 0.9 mg. The reduction in abrasion, which is predictive of an improvement in wear resistance, is mainly due to the fact that the introduction of suitable non-contact ultrasound and preheating contributes to obtaining a fine and uniformly distributed microstructure and therefore to an improvement in wear resistance.

(7) Room temperature tensile analysis of 24CrNiMoY alloy steel sample in example 2:

FIG. 15 is a room temperature tensile curve of the 24CrNiMoY alloy steel sample of this example, which is compared to the alloy steel sample of example 1, and the sample of example 2 has a tensile strength of 1061MPa and an average elongation of 15.8%. The tensile property of the sample is obviously improved, which is mainly due to the fact that the compactness of the alloy steel sample is improved and the grain size is obviously refined.

Example 3

As shown in FIGS. 1 and 16 to 22, the present embodiment is different from embodiment 1 in that the preheating temperature of the substrate preheating device 7 is 200 ℃.

And cutting a sample with a required size by using an electric spark cutting machine, and performing organization and performance characterization on the sample.

(1) Metallographic phase and density analysis of 24CrNiMoY alloy steel sample in example 3:

the alloy steel samples prepared in this example were subjected to a macroscopic metallographic analysis as shown in fig. 16. Gaps were observed between layers of the alloy steel sample, which was 99.63% dense as measured by archimedes drainage. The density reduction shows that the preheating temperature is further increased under the coordination of the two fields, so that a large amount of bubbles are generated in the metallurgical reaction in the molten pool, and part of the bubbles cannot escape from the molten pool and remain, thereby causing the residue of air hole gaps.

(2) Scanning texture analysis of 24CrNiMoY alloy steel sample in example 3:

FIG. 17 shows SEM morphology of pre-heating-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel samples, which mainly consists of a small amount of upper bainite and a coarse granular bainite structure. The coarsening of the structure is mainly that the preheating temperature under the double-field cooperation is too high at the moment, so that the temperature in a molten pool is higher, and the bainite structure is coarsened at the moment.

(3) XRD diffraction analysis of 24CrNiMoY alloy steel sample in example 3:

FIG. 18 is an X-ray diffraction pattern of a preheating-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, and a main phase of the 24CrNiMoY alloy steel sample is an alpha-Fe solid solution phase.

(4) EBSD analysis of 24CrNiMoY alloy steel samples in example 3:

FIG. 19 is an EBSD data analysis of pre-heat-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel samples. The statistics of the large and small angle grain boundaries shows that the proportion of the large angle grain boundaries is 53.5%, the proportion of the small angle grain boundaries is 46.5%, and the proportion of <111> twin grain boundaries is 11.3%. Due to the further increase of the preheating temperature, the prior austenite grain boundary size coarsened to 5.9 μm.

(5) Hardness data analysis of 24CrNiMoY alloy steel samples in example 3:

FIG. 20 is a graph showing the microhardness distribution of a preheated-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, wherein the average microhardness is significantly reduced to 330.6 +/-70 HV due to coarse granular bainite in the structure and coarsening of the grain size_0.2。

(6) Wear data analysis of 24CrNiMoY alloy steel samples in example 3:

FIG. 21 shows the appearance of a grinding crack of a preheated-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, and it is observed that the grinding crack pear trough of the alloy steel sample in the embodiment is relatively heavy and has severe oxidation adhesion abrasion, and the abrasion of the abraded sample is 5.3mg after being weighed before and after being weighed. Compared with the alloy steel samples in the embodiment 1 and the embodiment 2, the wear resistance of the alloy steel sample in the embodiment 3 is reduced because the sample structure is granular bainite and the strength and hardness of the granular bainite structure are lower.

(7) Room temperature tensile analysis of 24CrNiMoY alloy steel sample in example 3:

FIG. 22 is a room temperature tensile curve of the 24CrNiMoY alloy steel sample of this example, wherein the sample of example 3 has 675MPa tensile strength and 13.9% average elongation compared to the alloy steel sample of example 2. The sample compactness is reduced due to the occurrence of unfused pore defects between layers of the alloy steel sample, and the structure of the alloy steel sample is coarse granular bainite, so that the tensile property of the alloy steel sample is obviously reduced compared with that of the example 1 and the example 2.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of preheating a non-contact, ultrasonically assisted, direct laser deposition metallic material, comprising:

arranging an ultrasonic generator in a cabin of a laser additive manufacturing device, wherein the output end of the ultrasonic generator is not in contact with a substrate and a deposition layer, an included angle alpha is formed between the axis of the output end of the ultrasonic generator and the substrate, the axis of the output end of the ultrasonic generator is intersected with the axis of the laser output end of the laser additive manufacturing device, and the intersection point is positioned in a molten pool on the substrate;

assembling a preheating substrate device at the bottom of the base plate, wherein the preheating substrate device preheats the base plate;

the laser additive manufacturing device carries out laser deposition, the ultrasonic generator transmits ultrasonic waves to the molten pool in the laser deposition process, and the substrate preheating device continuously preheats;

2. The method for preheating a non-contact ultrasonic-assisted direct laser deposition metallic material as recited in claim 1, wherein a is 30-60 °.

3. The method as claimed in claim 1, wherein the power of the ultrasonic generator is 120-600W.

4. The method for preheating a non-contact ultrasonic-assisted direct laser deposition metal material according to claim 1, wherein the preheating temperature of the preheating substrate device is 50-200 ℃.

5. The method of claim 1, wherein the ultrasonic generator is suspended above the substrate by a support.