CN114472921B

CN114472921B - Method for preheating non-contact ultrasonic-assisted direct laser deposition of metal material

Info

Publication number: CN114472921B
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: 2023-05-26
Anticipated expiration: 2042-01-12
Also published as: CN114472921A

Abstract

The invention provides a method for preheating non-contact ultrasonic-assisted direct laser deposition of metal materials, 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 contacted with a substrate and a deposition layer; assembling a substrate preheating device at the bottom of the base plate, and preheating the base plate by the substrate preheating device; the laser additive manufacturing device performs laser deposition, and 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 the molten pool by taking air as a medium under the conditions of not contacting a substrate and not damaging the surface of a deposited sample in the whole deposition process, and simultaneously has a dual synergistic mechanism of a temperature field and a stress field, so that the prepared alloy steel material has the characteristics of fewer defects and better matching of the toughness of the tissue performance, and can meet the shape control and control application technical requirements of direct laser deposition high-performance metal parts.

Description

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

Technical Field

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

Background

In recent years, direct laser deposition has been widely used in large parts of complex and high performance as one of the short-process manufacturing techniques due to its unique processing method. However, some defects such as pores, cracks, inclusions, etc. may occur 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 some measure to control and reduce defects in the sample during deposition. The introduction of external physical field treatments to influence the solidification behavior of laser melt pools, controlling their tissue properties, has become a research hotspot. Therefore, how to utilize the unique forming method of the direct laser deposition process to introduce the external physical field to finally achieve the purpose of adjusting defects, tissues and performances 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 is subjected to fast melting and fast cooling processes, the areas are expanded due to melting and heating and contracted due to cooling, complex tensile stress and compressive stress can be generated, uneven stress distribution of each area in a sample enables the maximum tensile stress to exceed the maximum strength born by the material, and then the sample is cracked. In addition, the metal powder is melted by laser irradiation during the deposition process, and bubbles in the laser molten pool are generated due to the existence of protective gas in the deposition process, so that the bubbles do not escape from the molten pool after solidification of the molten pool is finished, and finally air holes are formed in the sample and remain. Meanwhile, the direct laser deposition alloy process is a typical unbalanced metallurgical process, and the structure phase transformation, the grain size, the number of phases and the like of the alloy process are all different due to the change of a temperature field and a stress field in a molten pool, so that how to scientifically and purposefully influence the solidification process of the laser molten pool by adding external field factors, and the alloy material with few crack and pore defects, fine structure and different types and numbers of phases is promoted to be formed, so that the matching of the regulation and control forming structure and the performance toughness is realized, and the alloy material has become a serious scientific research work.

Aiming at the characteristics of generating crack and pore defects of a deposited metal material and regulating and controlling the structure of alloy steel by a temperature field in the deposition process, the introduction of preheating can effectively reduce the temperature gradient between a base material and a deposition layer, further reduce the residual stress of the deposition layer, achieve the aim of slowing down crack initiation, and simultaneously preheat and change the solidification speed of a molten pool, thereby being beneficial to pore precipitation and regulating and controlling the structure of the structure. The introduction of the ultrasonic wave can effectively refine grains, regulate and control stress distribution among the deposition layers, and the ultrasonic wave can cause the change of the flowing state of the molten pool when being introduced into the molten pool, thereby achieving the effect of regulating and controlling air holes and tissues.

Research at home and abroad shows that independent preheating and ultrasonic application have obvious effects of regulating and controlling tissues and defects, and have been well applied in engineering practice. Most of the modes of introducing ultrasonic vibration adopt the vibration of the bottom of a substrate and the impact vibration of the surface of a deposition layer, but the ultrasonic vibration modes cannot be used for manufacturing and remanufacturing large-scale complex metal parts such as a high-speed railway brake disc, a nuclear power emergency diesel shaft, a rolling mill and the like, and the problems that auxiliary equipment is difficult to be suitable 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 simultaneously introduce two physical fields of preheating and non-contact ultrasonic into the process of directly laser depositing metal materials is not only a new scientific problem of double-field cooperative coupling effect, but also a new method for researching and developing high-efficiency regulation and control of defects and tissue properties in deposited metal materials. Therefore, two external-field composite auxiliary direct laser deposition is necessary to be studied to regulate and control the solidification behavior of a laser melting pool, a double-field synergistic action mechanism is established, the difficult problem that crack and pore defects are easy to occur and the matching of tissue performance and toughness is poor in the process of directly laser depositing metal parts is solved, the advanced double-field synergistic auxiliary laser direct deposition technology of high-performance alloy steel parts is obtained, and theoretical and technical foundation is laid for 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 preheating-non-contact ultrasonic composite auxiliary, and the principle of the method is that the unbalanced metallurgical solidification process of a laser molten pool is influenced based on a temperature field and stress field double-field synergistic mechanism and the changing requirement of an ultrasonic auxiliary mode, so that the defect of air hole cracks is eliminated, grains are thinned, the structure performance is regulated and controlled, and finally, the high-quality metal material with nondefective structure performance and obdurability matching is obtained. By preheating the substrate, the problem of overlarge temperature gradient between the substrate and the deposition layer is solved; the ultrasonic wave of the bracket is introduced into the molten pool in a mode of not contacting the substrate and the deposition layer, and the air medium is introduced into the molten pool, so that the defect that the ultrasonic device and the inside of the part cannot be assembled on a large part is solved; by the composite design of the two external field devices, preheating and non-contact ultrasonic treatment are simultaneously introduced into the process of directly laser depositing metal materials, so that a double-field auxiliary direct laser depositing process system is formed. The influence rule of the composite process technology on defect elimination and tissue performance toughness matching is clarified through the parameter study of the preheating process and the non-contact ultrasonic process, and a double-field cooperative regulation and control action mechanism is established; a novel method for obtaining the preheating-non-contact ultrasonic composite auxiliary direct laser deposition high-performance metal material.

The invention adopts the following technical means:

a method of pre-heating a non-contact ultrasound-assisted direct laser deposition metallic material, comprising:

the ultrasonic generator is arranged in a machine cabin of the laser additive manufacturing device, 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, so that the surface is kept bright and free of oxide scale;

placing a substrate preheating device on a workbench surface of a laser additive manufacturing device, wherein the substrate preheating device is positioned at the bottom of a substrate, and the substrate preheating device is used for preheating the substrate;

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

Based on the optimal technological parameters and optimized laser technological parameters of a single non-contact ultrasonic field, a substrate preheating device is utilized to preheat a substrate at different temperatures, and a direct laser deposition process is adopted to print samples with different ultrasonic parameters according to a designed scanning path.

After the laser deposition is finished, the laser additive manufacturing device, the substrate preheating device and the ultrasonic generator are closed.

Preferably, α is 30-60 °.

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

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

Preferably, the sonotrode is suspended above the substrate by a bracket for fixing the sonotrode and enabling adjustment of the angle α between the sonotrode 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 the molten pool by taking air as a medium under the conditions of not contacting a substrate and not damaging the surface of a deposited sample in the whole deposition process, and has the advantage of solving the technical problem that the traditional ultrasonic vibration mode cannot be equipped in the manufacture of large-sized parts. In addition, the process method for simultaneously and effectively introducing preheating and non-contact ultrasonic has a double synergistic action mechanism of a temperature field and a stress field, so that the prepared metal material has the characteristics of fewer defects and better matching of tissue performance and toughness, and can meet the demand of the shape control and control application technology of the direct laser deposition high-performance metal parts.

For the reasons, the 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 that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

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

FIG. 2 is a macroscopic metallographic schematic of a 24CrNiMoY alloy steel sample prepared in example 1 of the practice of the invention.

FIG. 3 is a scanning structure diagram of a 24CrNiMoY alloy steel sample prepared in example 1 of the present invention.

FIG. 4 is an XRD diffraction pattern of a 24CrNiMoY alloy steel sample prepared in example 1 of the practice of the invention.

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 a 24CrNiMoY alloy steel sample prepared in inventive example 1.

FIG. 7 is a schematic view of the wear of a 24CrNiMoY alloy steel sample prepared in example 1 of the present invention, wherein FIG. (a) is a low-power wear scar morphology and FIG. (b) is an enlarged morphology of the middle region of FIG. (a).

FIG. 8 is a room temperature tensile plot of a 24CrNiMoY alloy steel sample prepared in inventive example 1.

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

FIG. 10 is a histographic photograph of a 24CrNiMoY alloy steel sample prepared in example 2 of the present invention.

FIG. 11 is an XRD diffraction pattern of a 24CrNiMoY alloy steel sample prepared in example 2 of the present invention.

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 a 24CrNiMoY alloy steel sample prepared in inventive example 2.

FIG. 14 is a schematic view of the wear of a 24CrNiMoY alloy steel sample prepared in example 2 of the present invention, wherein FIG. (a) is a low-power wear scar morphology and FIG. (b) is an enlarged morphology of the middle region of FIG. (a).

FIG. 15 is a room temperature tensile plot of a 24CrNiMoY alloy steel sample prepared in inventive example 2.

FIG. 16 is a macroscopic metallographic schematic of a 24CrNiMoY alloy steel sample prepared in inventive example 3.

FIG. 17 is a scanning structure chart of a 24CrNiMoY alloy steel sample prepared in example 3 of the present invention.

FIG. 18 is an XRD diffraction pattern of a 24CrNiMoY alloy steel sample prepared in example 3 of the present invention.

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 a 24CrNiMoY alloy steel sample prepared in inventive example 3.

FIG. 21 is a schematic view of the wear of a 24CrNiMoY alloy steel sample prepared in example 3 of the present invention, wherein FIG. (a) is a low-power wear scar morphology and FIG. (b) is an enlarged morphology of the middle region of FIG. (a).

FIG. 22 is a room temperature tensile plot of a 24CrNiMoY alloy steel sample prepared in inventive example 3.

Detailed Description

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

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the 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 present invention. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.

The relative arrangement of the components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless it is specifically stated otherwise. Meanwhile, it should be clear that the dimensions of the respective parts shown in the drawings are not drawn in actual scale for 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. In all examples shown and discussed herein, any specific values should be construed as merely illustrative, and not a limitation. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.

In the description of the present invention, it should be understood that the azimuth or positional relationships indicated by the azimuth terms such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal", and "top, bottom", etc., are generally based on the azimuth or positional relationships shown in the drawings, merely to facilitate description of the present invention and simplify the description, and these azimuth terms do not indicate and imply that the apparatus or elements referred to must have a specific azimuth or be constructed and operated in a specific azimuth, and thus should not be construed as limiting the scope of protection of the present invention: the orientation word "inner and outer" refers to inner and outer relative to the contour of the respective component itself.

Spatially relative terms, such as "above … …," "above … …," "upper surface at … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial location relative 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 in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "above" or "over" other devices or structures would then be oriented "below" or "beneath" the other devices or structures. Thus, the exemplary term "above … …" may include both orientations of "above … …" and "below … …". The device may also be positioned in other different ways (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

In addition, the terms "first", "second", etc. are used to define the components, and are only for convenience of distinguishing the corresponding components, and the terms have no special meaning unless otherwise stated, and therefore should not be construed as limiting the scope of the present invention.

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. the ultrasonic generator 2 (the model of which is JZ 3000) is suspended in the cabin of the laser additive manufacturing device through the support 1, and the support 1 is adjusted to enable the ultrasonic generator 2 and the substrate 3 to be 60 degrees horizontally. Continuing to adjust the support 1 so that the axis of the output end of the ultrasonic generator 2 intersects with the axis of the laser output end 4 (the model of which is FL-Dlight 02-3000W) of the laser additive manufacturing device, and the intersection point is positioned in a molten pool on the substrate 3 (the material of which is Q235 substrate); and the output end of the ultrasonic generator 2 is positioned at a linear distance of 2cm from the red light mark on the substrate 3 (the mark emitted from the laser output end 3 onto 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 ultrasonic power output at the moment is 360W, and the amplitude is 21 mu m.

3. The laser process parameters (laser energy density 83.3J/mm) are adjusted on the laser control panel 6 of the laser output 4 ² ) And the lap rate is 40 percent and other laser process parameters. The defocus amount of the laser output end 4 was adjusted to 304mm.

4. A substrate preheating device 7 (model DB-XAB) was placed at the bottom of the substrate 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 to perform preheating-non-contact ultrasonic composite auxiliary direct laser deposition of alloy steel samples. In the laser material-increasing process, 24CrNiMoY alloy steel is used as a powder-feeding raw material, a 24CrNiMoY alloy steel sample is prepared in a serpentine scanning mode, and the shielding gas is Ar.

6. After the printing of the multilayer multipass samples is finished, clicking a stop button of the ultrasonic control panel 5, a stop button of the laser control panel 6 and turning off the substrate preheating device 7.

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

(1) Metallographic and compactness analysis of 24CrNiMoY alloy steel samples in example 1:

macroscopic metallographic analysis was performed on the alloy steel sample prepared in this example, as shown in fig. 2. Good bonding between layers of the alloy steel sample, no large unfused gap was observed, and the density of the sample was 99.63% as measured by archimedes' displacement method due to the introduction of ultrasound and the application of preheating, while helping the escape of bubbles in the molten pool with cooperative assistance to obtain good density.

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

fig. 3 shows the SEM morphology of a pre-heated-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, consisting essentially of upper and lower bainitic structures. It is clearly seen that the short rod-like theta-cementite is arranged in parallel along the direction of the Bainitic Ferrite (BF) main axis, which is typical of 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 pre-heat-noncontact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, the primary phase of the 24CrNiMoY alloy steel sample being the 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-noncontact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample. The large-angle grain boundary and the small-angle grain boundary are counted, the large-angle grain boundary proportion is 47.2%, the small-angle grain boundary proportion is 52.8%, the <111> twin boundary proportion is 13.5%, and the size of the prior austenite grain boundary is 2.5 mu m.

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

FIG. 6 is a graph showing the microhardness profile of a pre-heated, non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample having an average microhardness of 366.4.+ -. 39HV _0.2 。

(7) Analysis of wear data for 24CrNiMoY alloy steel samples in example 1:

FIG. 7 shows the wear scar morphology of a pre-heated-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, which was weighed back and forth to obtain a wear of 1.4mg.

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

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

Example 2

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

(1) Metallographic and compactness analysis of 24CrNiMoY alloy steel samples in example 2:

macroscopic metallographic analysis was performed on the alloy steel sample prepared in this example, as shown in fig. 9. No gaps were observed between the layers of the alloy steel sample, which was 99.83% dense as measured by archimedes' displacement method. Compared with example 1, the sample density of the example is obviously increased, which shows that under the parameters of the example, the ultrasonic wave and the preheating temperature in the molten pool accelerate the escape of bubbles, thereby being beneficial to obtaining a high-density sample.

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

fig. 10 shows the SEM morphology of a pre-heated-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample consisting essentially of upper bainite, lower bainite, and GB2 granular bainitic structure. And a number of fine precipitated carbides are present in the middle of the bainitic ferrite lath bundles, which are distributed at 50-80 deg. to the growth direction of BF lath bundles, which is typical of the lower bainitic structure. Furthermore, island structures were observed with few massive bainitic ferrite matrix and short rod-like growth along the lath, which is a form of GB2 granular bainitic. The existence of granular bainite in the structure is attributed to the increase of the preheating temperature, and the environment for forming the GB2 type granular bainite is satisfied. 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 pre-heated, non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, the main phases of the 24CrNiMoY alloy steel sample being 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 a pre-heat-noncontact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample. The large-angle grain boundary and the small-angle grain boundary are counted, the large-angle grain boundary proportion is 57.0%, the small-angle grain boundary proportion is 43.0%, the <111> twin boundary proportion is 26.3%, and the prior austenite grain boundary size is 0.9 mu m. At this time, the grain size was refined and the small-angle grain boundaries were reduced as compared with the data of example 1, which was attributed to the increase in the preheating temperature, resulting in a change in the transformation process of the structure in the molten pool.

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

FIG. 13 is a graph showing the microhardness profile of a pre-heated, non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample having an average microhardness of 390.6.+ -. 54HV _0.2 . The increase in hardness values is attributed to refinement of the sample grain size at this time.

(6) Analysis of wear data for 24CrNiMoY alloy steel samples in example 2:

FIG. 14 shows the wear scar morphology of the pre-heat-noncontact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, in which the pear grooves were observed to be shallower and only a few particles were exfoliated. The abrasion samples were weighed before and after to obtain an abrasion of 0.9mg. The reduction in abrasion predicts an increase in abrasion resistance, mainly due to the fact that the introduction of suitable non-contact ultrasound and preheating helps to obtain a fine and uniformly distributed microstructure, thus favoring an increase in abrasion resistance.

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

fig. 15 is a plot of the room temperature elongation of a 24CrNiMoY alloy steel sample of this example, the tensile strength of the sample of this example 2 was 1061MPa and the average elongation was 15.8% as compared to the alloy steel sample of example 1. The tensile property of the sample is obviously improved, which is mainly due to the improvement of the compactness of the alloy steel sample, and the grain size is obviously thinned.

Example 3

As shown in fig. 1, 16 to 22, this 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 adopting an electric spark cutting machine, and carrying out tissue and performance characterization on the sample.

(1) Metallographic and compactness analysis of 24CrNiMoY alloy steel samples in example 3:

macroscopic metallographic analysis was performed on the alloy steel sample prepared in this example, as shown in fig. 16. Gaps were observed from layer to layer of the alloy steel sample, which was 99.63% dense as measured by archimedes' displacement method. At this time, the decrease of the density indicates the further increase of the preheating temperature under the cooperation of the double fields, so that a large amount of bubbles are generated in the metallurgical reaction in the molten pool, and part of the bubbles can not escape from the molten pool and remain, thereby causing the residues of the air hole gaps.

(2) Scanning tissue analysis of 24CrNiMoY alloy steel samples in example 3:

FIG. 17 shows the SEM morphology of a pre-heated-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, consisting essentially of a small amount of upper bainite and a coarse granular bainitic structure. The coarsening of the structure is mainly that the preheating temperature under the cooperation of the double fields 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 pre-heat-noncontact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, the primary phase of the 24CrNiMoY alloy steel sample being the alpha-Fe solid solution phase.

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

FIG. 19 is an EBSD data analysis of a pre-heat-noncontact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample. The large-angle grain boundary and the small-angle grain boundary are counted, the large-angle grain boundary proportion is 53.5%, the small-angle grain boundary proportion is 46.5%, and the <111> twin boundary proportion is 11.3%. The prior austenite grain boundary size was coarsened to 5.9 μm due to a further increase in the preheating temperature.

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

FIG. 20 is a graph showing the microhardness profile of a pre-heated, non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, with a significant decrease in average microhardness of 330.6+ -70 HV due to coarse granular bainite and coarsening of grain size in this case _0.2 。

(6) Analysis of wear data for 24CrNiMoY alloy steel samples in example 3:

FIG. 21 is a graph showing the wear scar morphology of a pre-heated-non-contact ultrasonic composite assisted direct laser deposition 24CrNiMoY alloy steel sample, where the wear scar pear groove of the alloy steel sample in this example was observed to be relatively heavy and subject to severe oxidative adhesive wear, and the wear was obtained by weighing the worn sample before and after it was 5.3mg. Compared with the alloy steel samples of example 1 and example 2, the alloy steel sample of example 3 has a lower wear resistance because the sample structure is granular bainite and the granular bainite structure has a lower strength.

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

fig. 22 is a graph showing the room temperature tensile curve of a 24CrNiMoY alloy steel sample in this example, and the sample in example 3 has a tensile strength of 675MPa and an average elongation of 13.9% compared to the alloy steel sample in example 2. The sample compactness was reduced due to the occurrence of unfused pore defects between the layers of the alloy steel sample at this time, and the microstructure of the alloy steel sample at this time was coarse granular bainite, so that the tensile properties of the alloy steel sample were significantly reduced compared to examples 1 and 2.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims

1. A method of pre-heating a non-contact ultrasonic-assisted direct laser deposition metallic material, comprising:

the method comprises the steps that an ultrasonic generator is arranged in a machine cabin of a laser additive manufacturing device, 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 located in a molten pool on the substrate;

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

the laser additive manufacturing device performs 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 substrate;

after the laser deposition is finished, the laser additive manufacturing device, the substrate preheating device and the ultrasonic generator are closed;

the alpha is 30-60 degrees;

the power of the ultrasonic generator is 120-600W;

the preheating temperature of the substrate preheating device is 50-200 ℃;

the laser energy density output by the laser output end of the laser additive manufacturing device is 83.3J/mm ² ；

The metal material is 24CrNiMoY alloy steel.

2. A method of pre-heating a non-contact ultrasonic assisted direct laser deposition metal material according to claim 1, wherein the ultrasonic generator is suspended above the substrate by a bracket.