CN107400887A - A kind of method that ultrasonic burnishing strengthens laser cladding layer - Google Patents

Abstract

The invention provides a method for ultrasonic rolling to strengthen the laser cladding layer. First, the powder feeding laser cladding method is used to prepare the cladding layer on the surface of the substrate; and then the surface of the laser cladding layer is smoothed by milling; Then the surface of the smooth cladding layer is strengthened by ultrasonic rolling. The advantages of the present invention are: the introduction of ultrasonic rolling on the surface of the cladding layer makes the grains of the surface layer more refined, and produces a more uniform distribution of residual compressive stress and lower surface roughness, which greatly improves the wear resistance and corrosion resistance of the cladding layer. At the same time as the anti-oxidation and anti-fatigue performance, the subsequent grinding and polishing machining can be avoided, and the requirements of the parts for the surface quality and dimensional accuracy of the cladding layer can be directly met, thereby reducing the complexity and cost of the process.

Description

A Method of Ultrasonic Rolling Strengthening Laser Cladding Layer

technical field

The invention relates to the field of surface strengthening of metal materials, in particular to a method for strengthening laser cladding layers by ultrasonic rolling.

Background technique

Laser cladding technology is a process that uses high-energy-density laser beams to rapidly melt and solidify powder and substrate at the same time and achieve good metallurgical bonding. It has been widely used in the fields of material surface modification, remanufacturing engineering, and additive manufacturing. However, due to the uneven distribution of laser energy, the large difference in thermal properties between the powder and the substrate, and the fast melting and solidification rate of the cladding material, the temperature gradient between the cladding layer and the substrate is large, resulting in uneven solidification structure and inconsistent material shrinkage. , easy to form residual tensile stress. The existence of residual tensile stress in the cladding layer and the residual overlapping marks due to multi-pass cladding can easily induce the formation of cracks and easily deform the parts, which reduces the service performance, service life and reliability of the parts. Therefore, it is of great research significance to homogenize the structure of the cladding layer, reduce the residual tensile stress in the cladding layer, and improve the stress distribution state to further strengthen the laser cladding layer.

In response to the above problems, relevant scholars have proposed control methods to further reduce the residual stress of the cladding layer and refine the surface structure. The patent application with the patent number 201310214376.8 proposes a device and method for strengthening the laser cladding layer by ultrasonic shock, which uses ultrasonic shock to reduce the residual tensile stress of the laser cladding layer, refines the structure of the laser cladding layer, and makes the cladding layer comprehensive The mechanical properties are further enhanced. The patent application number 201610991838.0 discloses a method for mechanical surface shot peening to improve the overall fatigue resistance of the remanufactured laser cladding repair layer. It proposes to use dry + wet composite shot peening process to refine the surface structure and introduce residual compressive stress. Patent No. 200810155785.4 discloses a surface modification method for laser peening to strengthen the laser cladding layer. By introducing laser peening technology, the distribution state of residual stress in the cladding layer is changed, and the dendrite morphology at the bottom of the cladding layer is also affected. Changes were made to suppress the initiation and propagation of cracks and improve the quality of the cladding layer. However, no matter ultrasonic impact, mechanical shot peening or laser shot peening can reduce the residual tensile stress of the cladding layer and improve the performance of the cladding layer, but the obtained cladding layer has a large surface roughness and uneven residual compressive stress distribution. , needs to be processed through subsequent grinding and polishing, which increases the complexity and cost of the process.

Ultrasonic rolling technology is a new type of ultrasonic-assisted surface strengthening technology, which can realize the nano-grain on the surface of the material, and can significantly reduce the surface roughness. The patent with the application number 201610717398.X discloses a method of ultrasonic rolling composite laser remelting to improve the fatigue performance of welded joints, aiming at the problems of high roughness caused by laser remelting and fatigue cracks easily formed at the position of multiple remelting traces, Ultrasonic rolling technology is used to eliminate the adverse effects caused by laser remelting, and realize surface nanometerization, thereby further improving surface fatigue performance. The patent with the application number 201610352680.2 discloses a low-temperature assisted ultrasonic surface rolling strengthening device and method, which uses low-temperature heating to soften the material while applying ultrasonic rolling to obtain larger surface residues while refining the grains of the surface material of the workpiece. stress. A large number of studies have shown that the ultrasonic rolling process can significantly reduce the surface roughness of the material, obtain a more uniform distribution of residual compressive stress, and realize the nanonization of the surface grains, further improving the fatigue resistance of the material.

The present invention proposes that the surface of the cladding layer is strengthened by using the ultrasonic rolling process to obtain uniformly distributed residual compressive stress, a finer grained surface structure and a lower surface roughness value, and to eliminate the overlapping of multiple laser cladding layers. It can reduce the traces of bonding and reduce the subsequent processing steps and costs, thereby further improving the wear resistance, corrosion resistance, oxidation resistance and fatigue resistance of the cladding layer.

Contents of the invention

The purpose of the present invention is to provide a method for ultrasonic rolling to strengthen the laser cladding layer. By applying the ultrasonic rolling process on the surface of the cladding layer, the residual stress distribution state in the cladding layer can be changed, and the cladding layer can be thinned and homogenized. The microstructure can significantly reduce the surface roughness of the cladding layer, eliminate the overlapping marks of multiple laser cladding, reduce the subsequent processing steps and costs, and further improve the wear resistance, corrosion resistance, oxidation resistance and fatigue resistance of the cladding layer.

The technical scheme that the present invention solves the above problems is:

A method for strengthening the laser cladding layer by ultrasonic rolling, characterized in that a composite method combining laser cladding and ultrasonic rolling is used to strengthen the surface of the metal material, specifically comprising the following steps:

A) Install and fix the polished, cleaned and dried metal substrate on the fixture;

B) Preparation of high-performance, defect-free cladding layer by laser cladding technology: turn on the laser, move the laser coaxial powder feeding nozzle to the starting point of cladding, perform coaxial powder feeding laser cladding processing, select laser cladding process parameters including laser Power, scanning speed, spot diameter and powder feeding volume;

C) Milling the surface of the cladding layer by milling to obtain a surface layer with a smooth surface and good finish;

D) The cladding layer with smooth surface is mechanically strengthened by ultrasonic rolling treatment to obtain finer grains on the surface layer, make the distribution of residual compressive stress more uniform, and reduce the surface roughness of the cladding layer.

Further, the metal material is magnesium alloy, titanium alloy, aluminum alloy, bearing steel, mold steel or cast iron.

Further, the cladding powder in step B) is iron, nickel, cobalt powder, or iron-based, nickel-based, cobalt-based cermet powder mixed with WC, TiC or SiC ceramic particles.

Further, the range of laser cladding processing parameters in the step B) is: laser power 600-2000W, spot diameter 2-5mm, scanning speed 500-1500mm/min, powder feeding amount 10-25g/min, lap rate 30 %-60%.

Further, in the step B), the laser processing parameters are adjusted and the powder controller controls the thickness of the cladding layer to be 1-1.5 mm.

Further, the milling depth of the step C) is 0.2-0.5 mm is realized by controlling the feed rate of the milling cutter, and the surface roughness of the cladding layer after milling is Ra<0.8 μm.

Further, the range of ultrasonic rolling process parameters in step D) is: preload force 50-2000N, vibration amplitude 5-30μm, ultrasonic frequency 15KHz-80KHz, rolling speed 10m/min-50m/min, multi-pass rolling The pressure step distance is 0.2-1.5mm.

Further, the ultrasonic rolling treatment in the step E) adopts a full coverage processing method of reciprocating 5-20 times.

The present invention overcomes that under the laser cladding technology, although the cladding layer whose performance is significantly increased compared with the substrate can be prepared, due to the uneven distribution of laser energy, the large difference between the thermal physical properties of the powder and the base material, and the fast melting and solidification rate of the cladding material, etc. Factors, resulting in a large temperature gradient between the cladding layer and the base material, easy to form residual tensile stress. The surface of the cladding layer is strengthened by introducing ultrasonic rolling technology, which can significantly refine and homogenize the microstructure of the cladding layer, eliminate residual tensile stress and introduce residual compressive stress at the same time, and greatly improve the wear resistance and corrosion resistance of the cladding layer. Antioxidant and antifatigue properties.

In the present invention, because ultrasonic rolling is a chipless polishing strengthening process, compared with methods such as mechanical shot peening, laser shot peening and ultrasonic shot peening to strengthen the cladding layer, the surface of the strengthening layer has a very low roughness, so it can be avoided. Subsequent grinding, fine polishing and machining directly meet the requirements of the components for the surface quality and dimensional accuracy of the cladding layer, thereby reducing process complexity and cost.

The invention combines the advantages of laser cladding and ultrasonic rolling, and has good process controllability, high production efficiency and easy automatic control, which can further promote the application of laser cladding technology in the field of surface engineering, remanufacturing and additive materials. Large area applications in manufacturing.

Description of drawings

Fig. 1 is a processing flowchart of the acoustic rolling enhanced laser cladding layer according to the present invention.

In the picture:

1-fixture; 2-substrate; 3-cladding layer; 4-laser coaxial powder feeding nozzle; 5-milling cutter; 6-ultrasonic rolling device.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

In the present invention, a high-performance cladding layer is prepared on the surface of the metal base material through the coaxial powder-feeding laser cladding technology, and then the surface layer with a smooth surface and good finish is obtained by means of milling, and finally the cladding layer is smoothed by using the ultrasonic rolling technology. The surface is strengthened to directly meet the requirements of the parts for the surface quality and dimensional accuracy of the cladding layer. The processing flow chart is shown in Figure 1.

The present invention will be further described below in conjunction with drawings and embodiments.

Example 1

A) Install and fix the CGr15 bearing steel base material 2 on the fixture 1 after being polished, cleaned and dried;

B) Coaxial powder feeding method is used for laser cladding Co42 alloy powder processing, moving the laser coaxial powder feeding nozzle 4 to the starting point of cladding, and setting the laser processing parameters as follows: laser power is 600w, scanning speed is 500m/min , the diameter of the spot is 2mm, the amount of powder feeding is 10g/min, the overlap rate is 30%, the thickness of the cladding layer 3 is controlled to be 1.2mm, and argon gas is blown in to protect the molten pool, and the flow rate is 15L/min, as shown in Figure 1 as shown in (a);

C) Milling the surface of the cladding layer 3 by means of end milling, by controlling the feed rate of the milling cutter 5, a milling depth of 0.2 mm is achieved, and a surface layer with a roughness value Ra<0.8 μm is smooth and has a good finish, See (b) shown in Figure 1;

D) Ultrasonic rolling treatment is performed on the cladding layer 3 with a smooth surface, and a static pressure of 50N is applied under the condition that the rolling head is in good contact with the cladding layer 3, and the ultrasonic rolling process parameters are set as follows: vibration amplitude 5 μm, ultrasonic frequency 20KHz, rolling speed 10m/min, multi-pass rolling step 0.2mm. Under these process parameters, the ultrasonic rolling device 6 is turned on to perform 5 times of full coverage on the surface of the cladding layer, as shown in (c) in Figure 1.

Finally, the surface grain of the cladding layer is more refined, the distribution of residual compressive stress is more uniform, and the surface roughness value is lower, which can directly meet the requirements of parts for surface quality and dimensional accuracy.

Example 2

A) Install and fix the TC4 titanium alloy substrate 2 on the fixture 1 after grinding, cleaning and drying;

B) Coaxial powder feeding method is used for laser cladding Ni60 alloy powder processing, and the laser coaxial powder feeding nozzle 4 is moved to the starting point of cladding. The laser processing parameters are set as follows: laser power is 2000w, scanning speed is 1500m/min , the diameter of the spot is 5mm, the amount of powder feeding is 25g/min, the overlap rate is 60%, the thickness of the cladding layer is controlled to be 1.5mm, and argon gas is blown in to protect the molten pool, and the flow rate is 15L/min, as shown in Fig. 1 ( a) as shown;

C) Milling the surface of the cladding layer 3 by means of end milling, by controlling the feed rate of the milling cutter 5, a milling depth of 0.5 mm is achieved, and a surface layer with a roughness value Ra<0.8 μm is smooth and has a good finish, See (b) shown in Figure 1;

D) Perform ultrasonic rolling treatment on the cladding layer 3 with a smooth surface, apply a static pressure of 2000N under the condition that the rolling head is in good contact with the cladding layer, and set the ultrasonic rolling process parameters as: vibration amplitude 30μm, ultrasonic frequency 80KHz ,, Rolling speed 50m/min, multi-rolling step 1.5mm. Under these process parameters, the ultrasonic rolling device 6 is turned on to perform 20 times of full coverage on the surface of the cladding layer, as shown in (c) in Fig. 1 .

Finally, the surface grain of the cladding layer is more refined, the distribution of residual compressive stress is more uniform, and the surface roughness value is lower, which can directly meet the requirements of parts for surface quality and dimensional accuracy.

Example 3

A) Install and fix the Cr12MoV mold steel substrate 2 on the fixture 1 after grinding, cleaning and drying;

B) Coaxial powder feeding method is used for laser cladding WC-12CO powder processing, and the laser coaxial powder feeding nozzle 4 is moved to the starting point of cladding. The laser processing parameters are set as follows: laser power is 1500w, scanning speed is 1000m/ min, the diameter of the spot is 4mm, the powder feeding rate is 15g/min, the overlap rate is 40%, the thickness of the cladding layer is controlled to be 1.3mm, and argon gas is blown in to protect the molten pool, and the flow rate is 15L/min, as shown in Figure 1 as shown in (a);

C) The surface of the cladding layer 3 is milled by means of end milling, as shown in (b) of Figure 1, by controlling the feed rate of the milling cutter 5, a milling depth of 0.3 mm is achieved, and a roughness value Ra<0.8 μm is obtained. Smooth surface and good surface finish;

D) Perform ultrasonic rolling treatment on the cladding layer 3 with a smooth surface, apply a static pressure of 1000N under the condition that the rolling head is in good contact with the cladding layer, and set the ultrasonic rolling process parameters as: vibration amplitude 20μm, ultrasonic frequency 50KHz , rolling speed 30m/min, multi-rolling step 1mm. Under these process parameters, the surface of the cladding layer is reciprocated 15 times for full coverage processing, as shown in (c) in Figure 1.

Finally, the surface grain of the cladding layer is more refined, the distribution of residual compressive stress is more uniform, and the surface roughness value is lower, which can directly meet the requirements of parts for surface quality and dimensional accuracy.

The described embodiment is a preferred implementation of the present invention, but the present invention is not limited to the above-mentioned implementation, without departing from the essence of the present invention, any obvious improvement, replacement or modification that those skilled in the art can make Modifications all belong to the protection scope of the present invention.

Claims (8)

1. A method for ultrasonic rolling to strengthen the laser cladding layer, characterized in that, the composite method combining laser cladding and ultrasonic rolling is used to strengthen the surface of the metal material, specifically comprising the following steps: A) Install and fix the polished, cleaned and dried metal substrate (2) on the fixture (1); B) Prepare a high-performance, defect-free cladding layer by laser cladding technology: turn on the laser, move the laser coaxial powder feeding nozzle (4) to the starting point of cladding, perform coaxial powder feeding laser cladding processing, and select the laser cladding process Parameters include laser power, scanning speed, spot diameter and powder feeding volume; C) milling the surface of the cladding layer (3) by milling to obtain a surface layer with a smooth surface and good finish; D) The cladding layer (3) with a smooth surface is mechanically strengthened by ultrasonic rolling treatment to obtain more refined grains on the surface layer, so that the distribution of residual compressive stress is more uniform, and the surface roughness of the cladding layer (3) is reduced . 2 . The method for ultrasonically rolling strengthened laser cladding layer according to claim 1 , wherein the metal material is magnesium alloy, titanium alloy, aluminum alloy, bearing steel, mold steel or cast iron. 3. The method for ultrasonic rolling strengthened laser cladding layer according to claim 1, characterized in that, the cladding powder in the step B) is iron, nickel, cobalt powder, or mixed with WC, TiC or SiC ceramics Granular iron-based, nickel-based, cobalt-based cermet powder. 4. The method of ultrasonic rolling to strengthen the laser cladding layer according to claim 1, characterized in that the range of laser cladding processing parameters in the step B) is: laser power 600-2000W, spot diameter 2-5mm, The scanning speed is 500-1500mm/min, the powder feeding volume is 10-25g/min, and the overlapping rate is 30%-60%. 5. the method for ultrasonic rolling strengthened laser cladding layer according to claim 1, is characterized in that, in described step B), the thickness that adjusts laser processing parameter and powder controller control cladding layer (3) is 1- 1.5mm. 6. The method for ultrasonic rolling strengthened laser cladding layer according to claim 1, characterized in that, the milling depth of the step C) is 0.2-0.5 mm by controlling the feed rate of the milling cutter (5) , and the surface roughness of the cladding layer (3) after milling is Ra<0.8 μm. 7. The method of ultrasonic rolling to strengthen laser cladding layer according to claim 1, characterized in that, the range of ultrasonic rolling process parameters in the step D) is: pre-tightening force 50-2000N, vibration amplitude 5-30 μm , Ultrasonic frequency 15KHz-80KHz, rolling speed 10m/min-50m/min, multi-channel rolling step 0.2-1.5mm. 8 . The method of ultrasonic rolling to strengthen the laser cladding layer according to claim 1 , characterized in that, the ultrasonic rolling treatment in the step E) adopts a full-coverage processing method of reciprocating 5-20 times.