CN111235380A

CN111235380A - Control method for surface layer characteristic parameter gradient during damaged metal component repair

Info

Publication number: CN111235380A
Application number: CN202010112403.0A
Authority: CN
Inventors: 程思竹; 程秀全; 陈西宏; 刘晨; 高春瑾
Original assignee: Guangzhou Civil Aviation College
Current assignee: Guangzhou Civil Aviation College
Priority date: 2020-02-24
Filing date: 2020-02-24
Publication date: 2020-06-05
Anticipated expiration: 2040-02-24
Also published as: CN111235380B

Abstract

The invention discloses a method for controlling a surface layer characteristic parameter gradient during repairing a damaged metal component, which comprises the following steps: s1, cutting off the material near the damaged part of the damaged metal component to form a gap to be supplemented; s2, carrying out surface strengthening treatment on the surfaces of the notches; s3, cleaning the strengthened surface; s4, filling the cleaned gap with a material by a 3D printing method, and exceeding the initial outline of the damaged metal member; and S5, performing surface finishing on the filled material by adopting a cutting method according to the initial shape of the damaged metal member, thereby meeting the requirement of the precision of the shape profile of the damaged metal member. The technical scheme of the invention is beneficial to improving the mechanical property of the repaired damaged metal component.

Description

Control method for surface layer characteristic parameter gradient during damaged metal component repair

Technical Field

The invention relates to the technical field of damage repair of metal components, in particular to a control method of surface layer characteristic parameter gradient during damage metal component repair.

Background

In the process of implementing the invention, the inventor finds that at least the following problems exist in the prior art, at present, the metal material often has surface corrosion or fatigue crack in the using process, and the statistical data of domestic and foreign data shows that a great deal of economic loss is caused by the damage of the component every year, wherein part of the economic loss is the structural damage which can be repaired and reused. The simplest method of treating damaged metal parts is to simply treat the damaged part, such as removing corrosion products or cutting off micro cracks, and then continue to use the damaged part. The notch generated in this way will cause the strength of the component to be reduced, and certain potential safety hazard exists. Secondly, the common method is to fill the gap with materials, and the existing surfacing mode is widely applied, but has some problems, such as serious heat influence of a welding part, embrittlement of the materials, residual tensile stress on the surface of the surfacing part, reduction of the fatigue life of a component and the like. With continuous research of remanufacturing technology, a 3D printing technology gradually replaces a surfacing welding method to be used for repairing the appearance and strength of a damaged part of a component. Although the heat affected zone is much smaller in 3D printing compared to build-up welding, the mechanism of the heat affected is the same and similar results are still present, only to a different extent. The main performance of the 3D printing heat affected zone is characterized in that the surface of the repaired component has two aspects of parameter gradient characteristics: firstly, the residual tensile stress is gradually increased, and secondly, the crystal grains are gradually coarsened. However, the residual tensile stress on the surface or the coarse grains adversely affect the mechanical properties of the material and are not favorable for improving the fatigue strength of the repaired component.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the above-mentioned problems in the prior art. Therefore, the embodiment of the invention provides a method for controlling the characteristic parameter gradient of the surface layer when the damaged metal component is repaired, so that the strength and the fatigue life of the repaired component are improved.

The method for controlling the surface layer characteristic parameter gradient during the repair of the damaged metal component is characterized by comprising the following steps of:

s1, cutting off the material near the damaged part of the damaged metal component to form a gap to be supplemented;

s2, carrying out surface strengthening treatment on the surfaces of the notches;

s3, cleaning the strengthened surface;

and S4, filling the cleaned gap with materials by adopting a 3D printing method.

In an alternative or preferred embodiment, in step S2, the surface strengthening process is performed by impact strengthening, and the angle between the direction of impact and the surface is defined as δ, which is 90 ° ± 5 °.

In an alternative or preferred embodiment, in step S2, the surface strengthening treatment is performed by a pulsed laser shock processing technique.

In an alternative or preferred embodiment, in step S2, the surface strengthening treatment is performed by a shot peening technique.

In an alternative or preferred embodiment, in step S4, the filled printing material is the same material powder as the damaged metal member.

In an alternative or preferred embodiment, in step S4, the cleaned gap is filled with material by using a 3D printing method until the initial contour of the damaged metal member is exceeded; and then, according to the initial shape of the damaged metal component, performing surface finishing on the filled material by adopting a cutting method, thereby meeting the requirement of the precision of the shape profile of the damaged metal component.

Based on the technical scheme, the embodiment of the invention at least has the following beneficial effects: when the surface of the notch is subjected to impact strengthening, the characteristic of parameter gradient change from the surface to the inside can be obtained, firstly, the residual stress is changed and pulled by pressure and then reduced to zero, and secondly, the grain size is changed from small to large to the grain size of the original component. The parameter gradient change trends of the two characteristics are just opposite to the gradient change direction generated by subsequent 3D printing, so that the uniform stress distribution and the grain size are favorably obtained, and the mechanical performance of the repaired damaged metal component is favorably improved.

Drawings

In order to more clearly illustrate the technical solution in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly described below. It is clear that the described figures are only some embodiments of the invention, not all embodiments, and that a person skilled in the art can also derive other designs and figures from them without inventive effort.

FIG. 1 is a schematic structural view of a damaged metallic component with microcracks or corrosion present in an embodiment of the invention;

FIG. 2 is a flow chart of a repair of a damaged metallic component according to an embodiment of the present invention;

FIG. 3 is a partial schematic view of a notch in an embodiment of the present invention;

FIG. 4 is a schematic diagram illustrating the distribution of residual stress in the depth direction due to the impact strengthening of the notched surface in the embodiment of the present invention;

FIG. 5 is a schematic illustration of a local grain size distribution of a surface layer formed by notched surface impact reinforcement in an embodiment of the present invention;

FIG. 6 is a schematic diagram of the distribution of residual stress formed by 3D printing on the notch surface along the depth direction in the embodiment of the invention;

FIG. 7 is a schematic diagram of the local grain size distribution of the surface layer formed by 3D printing of the notch surface according to the embodiment of the invention;

fig. 8 is a schematic structural view of the damaged metal member after repair in the embodiment of the present invention.

Detailed Description

Reference will now be made in detail to the present preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.

In the description of the present invention, it is to be understood that the positional or orientational relationships, such as those indicated by center, longitudinal, lateral, length, width, thickness, upper, lower, front, rear, left, right, vertical, horizontal, top, bottom, inner, outer, clockwise, counterclockwise, axial, radial, circumferential, and the like, are based on the positional or orientational relationships shown in the drawings and are for convenience of description and simplicity of description only, and are not intended to indicate or imply that the device or element so referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus are not to be considered as limiting.

In the description of the present invention, the meaning of several is one or more, the meaning of a plurality is two or more, and larger, smaller, larger, etc. are understood as excluding the present number, and larger, lower, inner, etc. are understood as including the present number unless specifically defined otherwise. Furthermore, the descriptions of first and second are only for the purpose of distinguishing between technical features, and are not to be construed as indicating or implying relative importance or implying any number or order of indicated technical features.

In the description of the present invention, unless otherwise expressly limited, terms such as set, arranged, mounted, connected, fixed and the like should be construed broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in the present invention in consideration of the detailed contents of the technical solutions.

In the description of the present invention, unless otherwise expressly limited, a first feature may be located on or below a second feature in direct contact with the second feature, or the first feature and the second feature may be in indirect contact via intermediate media. Also, a first feature may be directly above or obliquely above a second feature, or merely that the first feature is at a higher level than the second feature. A first feature may be directly below or obliquely below a second feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

FIG. 1 shows a schematic view of a damaged metal component 10 in the presence of microcracks or corrosion.

Referring to fig. 2, a method for controlling a surface layer characteristic parameter gradient during damaged metal member repair includes the following steps:

s1, the material near the damaged portion 11 of the damaged metal member 10 is cut off to form a gap 12 to be supplemented, as shown in FIG. 3.

S2, the surface of the notch is preferably subjected to a surface strengthening treatment, and the surface strengthening treatment is preferably performed by impact strengthening, where δ is defined as an angle between the impact direction and the surface, and δ is 90 ° ± 5 °, and the impact direction is understood to be as perpendicular to the surface as possible. In addition, specifically, in this embodiment, the surface strengthening treatment method adopted is a pulse laser impact process technology, so that two parameter gradient characteristics are formed on the surface layer of the notch 12, that is, firstly, the residual stress is gradually changed from the large compressive stress to the small tensile stress from the surface to the inside and then returns to zero, as shown in fig. 4; secondly, local microscopic grains on the surface layer are gradually reduced from the smaller size to the larger size from the outside to the inside, as shown in fig. 5. In other embodiments, the surface strengthening treatment may be performed by shot blasting.

And S3, cleaning the strengthened surface.

And S4, filling the cleaned gap with a material by adopting a 3D printing method, wherein the filled printing material adopts the same material powder as the damaged metal member 10.

Specifically, in step S4, the cleaned gap 12 is filled with material by a 3D printing method until the initial contour of the damaged metal member 10 is slightly exceeded. Because a certain heat affected zone exists during 3D printing, two parameter gradient characteristics are generated on the surface of the notch when 3D printing is independently performed, namely, the residual stress is gradually changed into smaller compressive stress from the surface to the inside, namely, the larger tensile force is firstly, and then returns to zero, as shown in figure 6; secondly, local microscopic grains on the surface layer are gradually reduced to smaller sizes from the larger sizes from the outside to the inside, as shown in fig. 7. The pulse laser shock peening is performed before to form a reverse parameter gradient, and the results of the two processes are superposed to obtain more uniform residual stress and grain size distribution on the surface layer of the notch 12. Is beneficial to the repair of the component to obtain better mechanical property.

In step S4, since the 3D printing technology cannot obtain the precise contour dimension with the same precision as the cutting process for a while after the gap 12 is filled with the material, the 3D printing technology needs to perform the cutting process on the contour margin reserved in the 3D printing process according to the initial contour of the damaged metal component 10, so as to obtain the repaired component 20 with the same precision level as the originally designed component, as shown in fig. 8, it can be understood that the gap 12 in fig. 3 has been repaired, and the interface between the raw material and the filling material has the residual stress and the micro-grain size with uniform distribution.

While the embodiments of the present invention have been described in detail with reference to the drawings, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art.

Claims

1. A method for controlling the characteristic parameter gradient of a surface layer during the repair of a damaged metal component is characterized by comprising the following steps:

s3, cleaning the strengthened surface;

2. The method for controlling the characteristic parameter gradient of the surface layer during the repair of the damaged metal member as set forth in claim 1, wherein: in step S2, the surface strengthening treatment is performed by impact strengthening, and the angle between the impact direction and the surface is defined as δ, which is 90 ° ± 5 °.

3. The method for controlling the gradient of the characteristic parameter of the surface layer at the time of repairing the damaged metal member according to claim 1 or 2, wherein: in step S2, the surface strengthening treatment is performed by a pulsed laser shock processing technique.

4. The method for controlling the gradient of the characteristic parameter of the surface layer at the time of repairing the damaged metal member according to claim 1 or 2, wherein: in step S2, the surface strengthening treatment is performed by a shot peening technique.

5. The method for controlling the characteristic parameter gradient of the surface layer during the repair of the damaged metal member as set forth in claim 1, wherein: in step S4, the filled printing material uses the same material powder as the damaged metal member.

6. The method for controlling the characteristic parameter gradient of the surface layer during the repair of the damaged metal member as set forth in claim 1, wherein: in step S4, filling the cleaned gap with a material by a 3D printing method until the material exceeds the initial contour of the damaged metal member; and then, according to the initial shape of the damaged metal component, performing surface finishing on the filled material by adopting a cutting method, thereby meeting the requirement of the precision of the shape profile of the damaged metal component.