Metal material and component nondestructive shot peening surface strengthening method thereof

Abstract

The invention discloses a nondestructive shot peening surface strengthening method for a metal material and a component thereof, and belongs to the field of manufacturing of key metal materials and components thereof of high-end equipment. According to the method, a metal film or sheet is adopted as a middle layer medium, shot blasting craters are intercepted on the metal film or sheet in the shot blasting process of a metal material or a component, the mechanical shot blasting surface strengthening effect of the metal material or the component is optimized and enhanced in combination with a shot blasting process, and the defect of the craters left on the surface of the metal material or the component after shot blasting is eliminated. After nondestructive shot blasting is carried out, the surface hardness of the metal material or the component is remarkably improved, residual compressive stress is introduced into surface metal, no residual crater defect exists, and the fatigue life of the metal material or the component is further prolonged.

Description

Technical Field

[0001] The present invention belongs to the field of manufacturing key metal materials and components of high-end equipment, and relates to a method for non-destructive shot peening surface strengthening of metal materials and components thereof. Background Art

[0002] High-performance metal materials are widely used in high-end equipment manufacturing industries such as aerospace, rail transit, and national defense. The service performance of key metal materials and their components seriously affects the safe service of high-end equipment. During service, materials and components for high-end equipment are mainly subjected to static loads, cyclic loads, or alternating loads. Fatigue fracture, friction wear, and stress corrosion cracking are the main failure forms. Since failures such as fatigue fracture and stress corrosion cracking often occur under low stress and without precursors, the fracture of key metal components can cause major accidents and bring huge economic losses to related companies and society. Therefore, improving the service performance of key metal components for high-end equipment is a common technical requirement of the high-end equipment manufacturing industry.

[0003] Mechanical surface strengthening is the main fatigue life extension technology for high-strength aluminum alloy components, and mechanical shot peening is the mainstream technology in surface mechanical strengthening technology. However, mechanical shot peening surface strengthening fatigue life extension and stress corrosion resistance improvement are subject to the crater defects left by the projectile impacting the metal surface, because the "notch effect" caused by the crater defects is an important factor in promoting fatigue crack initiation. Crater defects have become a "bottleneck" restricting the mechanical shot peening surface strengthening of key metal materials or components. To this end, a non-destructive shot peening method is proposed in the present invention, which utilizes a metal film or thin sheet to be applied to the surface of the metal material or component to eliminate the mechanical shot peening crater defects on the surface of the metal material or component. By eliminating the crater defects caused by mechanical shot peening, the reliability and service life of metal materials or components for high-end equipment under static load, cyclic load, alternating load and corrosive environment loading conditions are improved, especially the fatigue life and stress corrosion cracking life are significantly improved.

[0004] Fatigue fracture is the main failure mode of key metal components under cyclic or alternating loads. In 1964, the International Organization for Standardization (ISO) in Geneva published a report that gave a descriptive definition of metal fatigue: "The change in the performance of metal materials or components under the repeated action of stress or strain is called fatigue." Fatigue of metal materials or components usually occurs when the stress is far lower than the yield strength of the material, without obvious plastic deformation and without signs, and its harm is extremely great. High-performance metal materials are widely used in high-end equipment manufacturing industries such as aerospace, rail transportation, etc. They are often used in key load-bearing components. They are subjected to static loads, cyclic loads or alternating loads for a long time during service. Therefore, fatigue fracture failure and stress corrosion cracking failure of high-performance metal materials and their components are difficult problems in the high-end equipment manufacturing industry.

[0005] The mutual restriction between the strength and toughness of metal materials is a theoretical problem encountered in fatigue life extension. The fatigue fracture process of metal materials usually goes through three main stages: crack initiation, crack propagation and instantaneous fracture. Since the life of the instantaneous fracture stage accounts for a very small proportion of the total fatigue life, the fatigue life of metal materials mainly consists of two parts: crack initiation life and crack propagation life. The focus of fatigue life extension of key metal components is crack initiation life and crack propagation life. Based on the classical fatigue fracture theory, improving the fatigue crack initiation life of metal materials or components requires improving the strength of metal materials, while improving the fatigue crack propagation life requires improving the toughness of metal materials. Since the strength and toughness of metal materials usually show a restrictive relationship, this brings theoretical difficulties to the fatigue life extension of key metal components. Under the action of cyclic loads and alternating loads, fatigue cracks usually initiate from the surface of metal materials and then extend to the inside. During the cyclic loading process, single-phase pure metal materials produce "intrusion" and "extrusion" of slip bands on the surface of the sample, and fatigue cracks usually initiate from the "notch" formed by the slip band. Multiphase alloy materials have complex microstructures, the surface of materials or components is usually not smooth, the geometric structure varies, and fatigue cracks usually initiate from the surface. Compared with the crack propagation life, the fatigue crack initiation life of metal materials usually accounts for more than 90% of the total fatigue life, so the fatigue life extension of metal materials focuses on improving their fatigue crack initiation life. Surface mechanical shot peening is the main fatigue life extension method for metal materials or components used in high-end equipment.

[0006] Surface mechanical shot peening can effectively inhibit the initiation of fatigue cracks and increase the fatigue crack initiation life of key metal components, thus becoming the main fatigue life extension technology and stress corrosion cracking resistance technology for high-performance metal materials and their components for high-end equipment. Mechanical shot peening surface strengthening causes severe plastic deformation of the surface metal of metal materials or components, refines the surface metal grains, produces a large number of dislocations, and introduces residual compressive stress, ultimately forming a gradient microstructure and residual compressive stress layer, which can effectively inhibit the initiation of fatigue cracks, thereby significantly improving the fatigue performance of metal materials or components. In addition, the introduction of compressive stress in the surface metal can offset the effect of static tensile loads, which plays an important role in improving the stress corrosion cracking resistance of high-performance metal materials and their components.

[0007] Mechanical shot peening is the mainstream surface mechanical strengthening fatigue life extension technology for metal materials or components, and is widely used in aerospace, rail transportation, nuclear power and other fields. Mechanical shot peening uses high-pressure gas to drive metal, ceramic or glass projectiles through a Venturi nozzle to impact the metal surface at high speed, causing the surface metal to undergo plastic deformation, achieving surface metal grain refinement, generating a large number of dislocations, forming a gradient structure and introducing residual compressive stress, thereby improving the fatigue crack initiation resistance of metal materials. Its advantage is that it is not limited by the shape of the workpiece and has significant cost advantages. However, whether it is shot peening with metal projectiles, ceramic projectiles, or glass projectiles, while achieving surface strengthening, it is inevitable to leave crater defects on the metal surface. This defect promotes fatigue crack initiation under fatigue load. In addition, improving the surface strengthening effect of mechanical shot peening requires increasing the shot peening intensity, but it will aggravate the crater defects, which is intuitively manifested as an increase in the surface roughness value of metal components. In fact, the surface strengthening fatigue life extension effect of mechanical shot peening depends on the coupling effect of the positive contribution of surface strengthening and the negative contribution of surface crater defects. In the 1980s, Wang Renzhi and others from the Beijing Institute of Aeronautical Materials conducted a study on the relationship between the mechanical shot peening strain layer and fatigue strength of high-strength aluminum alloy surfaces. They found that mechanical shot peening can significantly improve the fatigue properties of high-strength aluminum alloys in the high stress area of ​​the SN curve, but has no obvious effect near the fatigue strength, which is mainly attributed to the surface crater defects formed after mechanical shot peening. [1] The Benedetti team at the University of Trento in Italy found that the fatigue life extension effect of mechanical shot peening is a complex interaction between residual stress and roughness. Shot peening with smaller pellets is more effective in improving fatigue performance because larger pellets increase the surface roughness of the material. [2] Research by Rodopoulos' team at the University of Shefield in the UK shows that surface roughness and residual stress distribution are the decisive parameters for improving fatigue performance by conventional mechanical shot peening. Residual compressive stress improves the resistance of high-strength aluminum alloys to fatigue crack initiation, while surface roughening reduces the fatigue life of engineering components by allowing earlier initiation and faster expansion of short fatigue cracks. [3] The study shows that the fatigue life of the samples of 50CrMnMoVNb spring steel after mechanical shot peening is increasingly dispersed as the stress amplitude decreases, and the surface crater defect is the main influencing factor. [4]. For this reason, the surface crater defects caused by mechanical shot peening are unfavorable factors for the fatigue life extension of metal materials or components. It significantly weakens the fatigue life extension effect of mechanical shot peening surface strengthening. To further improve the fatigue life extension effect of mechanical shot peening surface strengthening, it is necessary to retain the surface strengthening effect of mechanical shot peening while eliminating the crater defects caused by shot peening. The surface crater defects caused by mechanical shot peening have become the "bottleneck" of the current mechanical shot peening surface strengthening fatigue life extension efficiency. Since the birth of mechanical shot peening surface strengthening technology, the "pain point" of this technology has always existed, and new strategies are urgently needed to eliminate the crater defects left by mechanical shot peening on the surface of high-strength aluminum alloys.

[0008] The present invention applies a metal film or sheet to the surface of the metal material or component to be sprayed, and then performs shot peening surface strengthening. After the shot peening is completed, the metal film or sheet is removed from the surface of the metal material or component to obtain a non-destructive shot peening surface strengthening effect. The method can significantly improve the fatigue life, wear resistance, stress corrosion cracking resistance and electrochemical impedance uniformity of the metal material or component to be sprayed. The method is simple to operate, and has a significant effect on improving the fatigue cracking and stress corrosion cracking of high-performance metal materials and their components. It has great application value and broad application prospects.

[0009] References:

[0010] References [1] Wang Renzhi, Li Xiangbin, Wu Heng. Relationship between surface shot peening strain layer and fatigue strength of high-strength aluminum alloy [J]. Acta Aeronautica Sinica, 1985, 6(3): 250-257.

[0011] Literature[2]M.Benedetti,V.Fontanari,M.Bandini,D.Taylor.Multiaxial fatigueresistance of shot peened high-strength aluminum alloys[J].InternationalJournal of Fatigue,2014,61:271-282.

[0012] Literature [3] CARodopoulos, SACurtis, ERRios, JSRomero. Optimization of the fatigue resistance of 2024-T351 aluminum alloys by controlled shotpeening-methodology, results and analysis [J]. International Journal of Fatigue, 2004, 26: 849-856.

[0013] Literature[4]DQQWang,Q.Wang*,YKZhu,P.Zhang,ZJZhang,CXRen,XWLi*,ZFZhang*.Evaluating the fatigue cracking risk of surface strengthened50CrMnMoVNb spring steel with abnormal life time distribution[J].MaterialsScience&Engineering A, 2018,732:192-204. Summary of the invention

[0014] The purpose of the present invention is to provide a non-destructive shot peening surface strengthening method for metal materials and components, which uses a metal film or a thin sheet to apply to the surface of the metal material or component to be shot peened and then perform shot peening surface strengthening. After the shot peening is completed, the metal film or the thin sheet is removed from the surface of the metal material or component to obtain a non-destructive shot peening surface strengthening effect. This method can significantly improve the fatigue life, wear resistance, stress corrosion cracking resistance and electrochemical impedance uniformity of the metal material or component to be shot peened.

[0015] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0016] A method for non-destructive shot peening surface strengthening of a metal material and its components, comprising the following steps:

[0017] Step 1. Use high-pressure air to clean the surface of metal materials or components until there is no dust, sand, or metal debris on the surface; specifically, use high-pressure air to impact the surface 1 to 3 times; the air pressure is 0.02MPa to 1.0MPa;

[0018] Step 2. Apply lubricating medium to the cleaned surface of the metal material or component; the lubricating medium is 3# lithium-based grease or engine oil;

[0019] Step 3. Fix the metal material or component after applying it on its surface; the effective thickness of the metal film or sheet is 0.01 mm to 0.50 mm, and the material is one or more of aluminum and aluminum alloy, titanium and titanium alloy, stainless steel, high-temperature alloy, copper and copper alloy; the strength or hardness ratio of the metal film or sheet to the metal material or component as the substrate is 0.2 to 2.0; the fixing methods include mechanical clamping, rope binding, and electromagnetic adsorption;

[0020] Step 4. Roll brush the metal film or sheet; use the roller brush to brush 1 to 5 times;

[0021] Step 5. Shot peening is performed on the side of the metal material covered with the metal film or sheet; during the shot peening process, the types of shots include cast steel shots, ceramic shots, composite shot or glass shot, and the shot particle size is 0.02mm to 0.6mm; the shot peening intensity is 0.01A to 0.50A, and the shot peening coverage is 80% to 500%;

[0022] Step 6. After the shot peening is completed, the metal sheet or film is removed, and the metal material or component is cleaned until no lubricating medium remains on the surface, so as to obtain a metal material or component with a non-destructive shot peening surface strengthening effect; an organic solvent is used for cleaning, wherein the organic solvent includes gasoline and ethanol.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention uses a metal film or sheet as an intermediate layer medium. During the shot peening process of the metal material or component, the shot peening craters are retained on the metal film or sheet. The shot peening process is optimized to enhance the mechanical shot peening surface strengthening effect of the metal material or component, and eliminate the crater defects remaining on the surface of the metal material or component after shot peening. After non-destructive shot peening, the surface hardness of the metal material or component is significantly improved, residual compressive stress is introduced into the surface metal, and no residual crater defects are left on the surface, and the fatigue life of the metal material or component will be further improved. In addition, by introducing residual compressive stress into the surface of the metal material or component, no residual crater defects remain on the surface, which reduces stress concentration during loading, and more effectively improves the stress corrosion cracking performance of the metal material or component in sensitive corrosive media. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The original surface morphology and non-destructive shot peening surface morphology of 7075 aluminum alloy plate at the same magnification; (a) the original machined surface of 7075 aluminum alloy, optical microscope 500X, (b) the non-destructive shot peening surface of 7075 aluminum alloy, optical microscope 500X;

[0026] Figure 2 The cross-sectional morphologies of 7075 aluminum alloy plates after ordinary shot peening and non-destructive shot peening at the same magnification; (a) the cross-sectional morphology of 7075 aluminum alloy after ordinary shot peening, (b) the cross-sectional morphology of 7075 aluminum alloy after non-destructive shot peening.

[0027] Figure 3 This is a photo of the surface morphology of 7075 aluminum alloy after shot peening with ceramic shots. DETAILED DESCRIPTION

[0028] The present invention will be further described in the following examples, but the present invention is not limited thereto.

[0029] The present invention provides a method for non-destructive shot peening surface strengthening of a metal material and its components, comprising the following steps:

[0030] Step 1. Use high-pressure air with a pressure of 0.02MPa to 1.0MPa to impact the metal material or component for 1 to 3 rounds to clean the surface until there is no dust, sand, or metal debris on the surface;

[0031] Step 2. Apply lubricating medium 3# lithium-based grease or engine oil to the cleaned surface of the metal material or component;

[0032] Step 3. After applying a metal film or sheet with an effective thickness of 0.01 mm to 0.50 mm on the surface of a metal material or component, fix it by mechanical clamping, rope binding or electromagnetic adsorption; wherein the material of the metal film or sheet is one or more of aluminum and aluminum alloys, titanium and titanium alloys, stainless steel, high-temperature alloys, copper and copper alloys; the strength or hardness ratio of the metal film or sheet to the metal material or component as a substrate is 0.2 to 2.0;

[0033] Step 4. Use a roller brush to brush the metal film or sheet for 1 to 5 rounds;

[0034] Step 5. Use cast steel shot, ceramic shot, composite shot or glass shot with a particle size of 0.02 mm to 0.6 mm to shot peen the side of the metal material covered with the metal film or sheet; wherein the shot peening intensity is 0.01A to 0.50A, and the shot peening coverage is 80% to 500%;

[0035] Step 6. After the shot peening is completed, the metal sheet or film is removed, and the metal material or component is cleaned with an organic solvent until no lubricating medium remains on the surface, thereby obtaining a metal material or component with a non-destructive shot peening surface strengthening effect; wherein the organic solvent includes gasoline and ethanol.

[0036] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0037] Example 1 Non-destructive shot peening surface strengthening of a 7075 aluminum alloy plate.

[0038] (1) Surface cleaning of 7075 aluminum alloy plate. The size of 7075 aluminum alloy plate is 150mm×100mm×10mm. High-pressure gas with a pressure of 0.6MPa is used to impact the surface of 7075 aluminum alloy plate for 3 rounds to clean the dust, sand, metal chips and other attachments on the surface of 7075 aluminum alloy plate.

[0039] (2) Apply lubricating medium on the surface of 7075 aluminum alloy plate. Apply 3# lithium-based grease (yellow glycerin) evenly on the surface of 7075 aluminum alloy plate.

[0040] (3) Apply aluminum sheet to the surface of 7075 aluminum alloy plate. The thickness of aluminum sheet is 0.15mm. Use scissors to cut 150×100mm applied sheet from the aluminum sheet. The hardness ratio of aluminum sheet to 7075 aluminum alloy is 1.0. In the natural state, aluminum sheet is usually bent. Align the four sides of aluminum sheet with 7075 aluminum alloy plate, press the two sides of aluminum sheet on the surface of 7075 aluminum alloy plate, and clamp the aluminum sheet on the surface of 7075 aluminum alloy plate with clamps around the plate.

[0041] (4) Rolling and brushing the aluminum flakes. Use a clean rolling brush to press the aluminum flakes onto the surface of the 7075 aluminum alloy plate, and squeeze out the excess lubricating medium between the aluminum flakes and the surface of the 7075 aluminum alloy plate;

[0042] (5) Shot peening: In the shot peening process, ceramic shots were used as shot media, the shot diameter was 0.2 mm, the shot peening coverage was 150%, the shot peening intensity was 0.10A, and a shot peening machine was used to peen the surface of the 7075 aluminum alloy plate with aluminum flakes applied thereon.

[0043] (6) Remove the aluminum sheet. After shot peening, remove the clamps around the 7075 aluminum alloy plate and gently remove the aluminum sheet. Clean the surface of the 7075 aluminum alloy plate. Use anhydrous ethanol to clean the surface of the 7075 aluminum alloy plate and remove the 3# lithium-based grease (yellow glycerin) on the surface. The original surface morphology is as follows: Figure 1 As shown in (a), the surface morphology of the non-destructive shot peening is as follows Figure 1 (b) as shown.

[0044] Finally, scanning electron microscopy was used to characterize the cross-sectional morphology of ordinary shot peening and non-destructive shot peening. The original cross-sectional morphology is shown in Figure 2. Figure 2 As shown in (a), the cross-sectional morphology of non-destructive shot peening is as follows Figure 2 (b) As shown. After testing, the surface roughness Ra value is 0.36μm; Rz value is 3.18μm. The average microhardness of the matrix is ​​178HV 0.2 The maximum microhardness of the surface layer after non-destructive shot peening is 208HV 0.2 , the depth of the hardened layer is 125μm, the maximum residual stress occurs at 83μm in the sub-surface layer, the maximum residual stress is -128MPa, and the depth of the residual stress layer is 226μm.

[0045] Comparative Example 1: Shot peening surface strengthening of 7075 aluminum alloy plate

[0046] (1) Surface cleaning of 7075 aluminum alloy plate. The size of 7075 aluminum alloy plate is 150mm×100mm×10mm. High-pressure gas with a pressure of 0.6MPa is used to impact the surface of 7075 aluminum alloy plate for 3 rounds to clean the dust, sand, metal chips and other attachments on the surface of 7075 aluminum alloy plate.

[0047] (2) Shot peening: In the shot peening process, ceramic shots are used as shot media, the shot diameter is 0.2 mm, the shot peening coverage is 150%, the shot peening intensity is 0.10A, and a shot peening machine is used to peen the surface of the 7075 aluminum alloy plate.

[0048] (3) Remove the sample. After the shot peening is completed, remove the 7075 aluminum alloy plate from the shot peening machine.

[0049] Finally, the surface morphology of 7075 aluminum alloy after ceramic shot peening is as follows Figure 3 As shown. After testing, the surface roughness Ra value is 2.35μm; Rz value is 12.46μm. The average microhardness of the matrix is ​​178HV 0.2 The maximum microhardness of the surface layer after shot peening is 216HV 0.2 The depth of the hardened layer is 138μm, the maximum residual stress occurs at 96μm in the sub-surface layer, the maximum residual stress is -136MPa, and the depth of the residual stress layer is 274μm.

[0050] Example 2 Non-destructive shot peening surface strengthening of a 304 stainless steel tube

[0051] (1) Surface cleaning of 304 stainless steel pipe. The dimensions of 304 stainless steel pipe are 200mm in outer diameter, 180mm in inner diameter, 10mm in wall thickness and 100mm in length. High-pressure gas with a pressure of 0.6MPa is used to impact the surface of 304 stainless steel pipe for 2 rounds to clean the dust, sand, metal chips and other attachments on the surface of 304 stainless steel pipe.

[0052] (2) Apply lubricating medium on the surface of 304 stainless steel pipe. Apply 3# lithium grease (yellow glycerin) evenly on the surface of 304 stainless steel pipe.

[0053] (3) Apply 304 stainless steel sheet to the surface of 304 stainless steel tube. The thickness of 304 stainless steel sheet is 0.2mm. Use scissors to cut 630×100mm application sheet from 304 stainless steel sheet. The hardness ratio of 304 stainless steel sheet to 304 stainless steel is 2.0. In the natural state, 304 stainless steel sheet is usually curved. Let the arc surface of 304 stainless steel sheet be consistent with the surface of 304 stainless steel tube. Wrap 304 stainless steel sheet and 304 stainless steel tube together. Slightly overlap 304 stainless steel sheet to leave space for deformation and elongation of 304 stainless steel sheet after shot peening. Use fine steel wire to firmly fix 304 stainless steel sheet on the surface of 304 stainless steel tube. Use fine steel wire to fix 3-4 times. So far, the fixation is complete.

[0054] (4) Roller brush compacts the 304 stainless steel sheet. Use a clean roller brush to compact the 304 stainless steel sheet on the surface of the 304 stainless steel tube, and squeeze out the excess lubricating medium between the 304 stainless steel sheet and the surface of the 304 stainless steel tube;

[0055] (5) Shot peening: Shot peening is performed on the surface of the 304 stainless steel pipe with the 304 stainless steel sheet applied thereon using a shot peening machine, cast steel shots with a diameter of 0.6 mm, a shot peening coverage of 200%, and a shot peening intensity of 0.15A.

[0056] (6) Remove the 304 stainless steel sheet. After shot peening, cut off the wire that fixes the 304 stainless steel sheet and remove it gently. Clean the surface of the 304 stainless steel pipe. Use anhydrous ethanol to clean the surface of the 304 stainless steel pipe and remove the 3# lithium grease (yellow glycerin) on the surface.

[0057] Finally, after testing, the surface roughness Ra value of 304 stainless steel tube is 0.24μm; Rz value is 2.12μm. The average microhardness of the matrix is ​​166HV 0.3 The maximum microhardness of the surface layer after non-destructive shot peening is 269HV 0.3 The depth of the hardened layer is 638μm, the maximum residual stress occurs at 136μm in the sub-surface layer, the maximum residual stress is -364MPa, and the depth of the residual stress layer is 689μm.

[0058] Comparative Example 2 Shot Peening Surface Strengthening of a 304 Stainless Steel Tube

[0059] (1) Surface cleaning of 304 stainless steel pipe. The dimensions of 304 stainless steel pipe are 200mm in outer diameter, 180mm in inner diameter, 10mm in wall thickness and 100mm in length. High-pressure gas with a pressure of 0.60MPa is used to impact the surface of 304 stainless steel pipe for 2 rounds to clean the dust, sand, metal chips and other attachments on the surface of 304 stainless steel pipe.

[0060] (2) Shot peening: Shot peening is performed on the surface of the 304 stainless steel pipe with the 304 stainless steel sheet applied thereon using a shot peening machine, cast steel shots with a diameter of 0.6 mm, a shot peening coverage of 200%, and a shot peening intensity of 0.15A.

[0061] (3) Remove the sample. After shot peening is completed, remove the fixed 304 stainless steel pipe from the shot peening machine.

[0062] Finally, after testing, the surface roughness Ra value of 304 stainless steel tube is 4.24μm; Rz value is 16.12μm. The average microhardness of the matrix is ​​166HV 0.3 The maximum microhardness of the surface layer after non-destructive shot peening is 283HV 0.3The depth of the hardened layer is 741μm, the maximum residual stress occurs at 153μm in the sub-surface layer, the maximum residual stress is -392MPa, and the depth of the residual stress layer is 782μm.

[0063] Example 3: Non-destructive shot peening surface strengthening of a TC4 titanium alloy plate

[0064] (1) Surface cleaning of TC4 titanium alloy plate. The size of TC4 titanium alloy plate is 200mm×200mm×10mm. High-pressure gas with a pressure of 0.6MPa is used to impact the surface of TC4 titanium alloy plate for one round to clean the dust, sand, metal chips and other attachments on the surface of TC4 titanium alloy plate.

[0065] (2) Apply lubricating medium on the surface of TC4 titanium alloy plate. Apply 3# lithium grease (yellow glycerin) evenly on the surface of 304 stainless steel pipe.

[0066] (3) Apply titanium sheet to the surface of TC4 titanium alloy plate. The thickness of titanium sheet is 0.10mm. Use scissors to cut 200×200mm applied sheet on the titanium sheet. The hardness ratio of titanium sheet to TC4 titanium alloy is 0.5. In the natural state, titanium sheet is usually curved. Let the arc surface of titanium sheet be tangent to the surface of TC4 titanium alloy plate. Align the four sides of titanium sheet with TC4 titanium alloy plate, press the two sides of titanium sheet on the surface of TC4 titanium alloy plate, and use clamps to clamp the titanium sheet on the surface of TC4 titanium alloy plate around the TC4 titanium alloy plate.

[0067] (4) Rolling and brushing the titanium flakes. Use a clean rolling brush to press the titanium flakes onto the surface of the TC4 titanium alloy plate, and squeeze out the excess lubricating medium between the titanium flakes and the surface of the TC4 titanium alloy plate;

[0068] (5) Shot peening: The surface of the TC4 titanium alloy plate with the titanium sheet applied thereon was shot peened using a shot peening machine, ceramic shots with a diameter of 0.2 mm, a shot peening coverage of 150%, and a shot peening intensity of 0.15A.

[0069] (6) Remove the titanium sheet. After shot peening, cut off the steel wire that fixes the titanium sheet and remove it gently to avoid scratching the surface of the TC4 titanium alloy plate. Clean the surface of the TC4 titanium alloy plate. Use anhydrous ethanol to clean the surface of the TC4 titanium alloy plate and remove the 3# lithium-based grease (yellow glycerin) on the surface.

[0070] Finally, after testing, the surface roughness Ra value of TC4 titanium alloy plate is 0.38μm; Rz value is 3.59μm. The microhardness of the matrix is ​​uniformly 310HV 0.3 The maximum microhardness of the surface layer after non-destructive shot peening is 368HV 0.2The depth of the hardened layer is 270μm, the maximum residual stress occurs at 25μm in the sub-surface layer, the maximum residual stress is -448MPa, and the depth of the residual stress layer is about 130μm.

[0071] Comparative Example 3 Shot Peening Surface Strengthening of a TC4 Titanium Alloy Plate

[0072] (1) Surface cleaning of TC4 titanium alloy plate. The size of TC4 titanium alloy plate is 200mm×200mm×10mm. High-pressure gas with a pressure of 0.6MPa is used to impact the surface of TC4 titanium alloy plate for one round to clean the dust, sand, metal chips and other attachments on the surface of TC4 titanium alloy plate.

[0073] (2) Shot peening: The surface of the TC4 titanium alloy plate with the titanium sheet applied thereon was shot peened using a shot peening machine, ceramic shots with a diameter of 0.2 mm, a shot peening coverage of 150%, and a shot peening intensity of 0.15A.

[0074] (3) Remove the sample. After shot peening is completed, remove the TC4 titanium alloy plate from the shot peening machine.

[0075] Finally, after testing, the surface roughness Ra value of TC4 titanium alloy plate is 1.29μm; Rz value is 8.89μm. The microhardness of the matrix is ​​uniformly 310HV 0.3 The maximum microhardness of the surface layer after shot peening is 375HV 0.2 The depth of the hardened layer is about 300μm, the maximum residual stress appears at 35μm in the sub-surface layer, the maximum residual stress is -460MPa, and the depth of the residual stress layer is 149μm.

Claims

1. A method for non-destructive shot peening surface strengthening of metal materials and components thereof, characterized in that: The following steps are involved: Step 1. Use high-pressure air to clean the surface of metal materials or components until there is no dust, sand, or metal debris on the surface; Step 2. Apply lubricating medium to the cleaned surface of the metal material or component; Step 3. Apply a metal film or sheet to the surface of the metal material or component and then fix it; Step 4. Roll brushing on the metal film or sheet; Step 5. Shot peening the side of the metal material covered with the metal film or sheet; Step 6. After the shot peening is completed, the metal sheet or film is removed, and the metal material or component is cleaned until no lubricating medium remains on the surface, thereby obtaining a metal material or component with a non-destructive shot peening surface strengthening effect.

2. A method for non-destructive shot peening surface strengthening of metal materials and components thereof according to claim 1, characterized in that: In step 1, the surface cleaning process is specifically as follows: using high-pressure air to impact the surface 1 to 3 times; The air pressure is 0.02MPa~1.0MPa.

3. The method for non-destructive shot peening surface strengthening of metal materials and components thereof according to claim 1, characterized in that: In step 2, the lubricating medium is 3# lithium-based grease or engine oil.

4. A method for non-destructive shot peening surface strengthening of metal materials and components thereof according to claim 1, characterized in that: In step 3, the effective thickness of the metal film or sheet is 0.01 mm to 0.50 mm, and the material is one or more of aluminum and aluminum alloys, titanium and titanium alloys, stainless steel, high-temperature alloys, copper and copper alloys; Methods for fixing metal films or sheets include mechanical clamping, rope bundling, and electromagnetic adsorption.

5. The method for non-destructive shot peening surface strengthening of metal materials and components thereof according to claim 1, characterized in that: In step 3, the strength or hardness ratio of the metal film or sheet to the metal material or component serving as the substrate is 0.2 to 2.

0.

6. The method for non-destructive shot peening surface strengthening of metal materials and components thereof according to claim 1, characterized in that: In step 4, use a roller brush for 1 to 5 rounds.

7. The method for non-destructive shot peening surface strengthening of metal materials and components thereof according to claim 1, characterized in that: In step 5, during the shot peening process, the types of shots include cast steel shots, ceramic shots, composite shot or glass shot, and the shot particle size is 0.02 mm to 0.6 mm.

8. The method for non-destructive shot peening surface strengthening of metal materials and components thereof according to claim 1, characterized in that: In step 5, the shot peening intensity is 0.01A to 0.50A, and the shot peening coverage is 80% to 500%.

9. The method for non-destructive shot peening surface strengthening of metal materials and components thereof according to claim 1, characterized in that: In step 6, an organic solvent is used for cleaning, wherein the organic solvent includes gasoline and ethanol.

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