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A surface strengthening method for reducing the porosity of laser additive parts

A laser additive and surface strengthening technology, used in the fields of laser shock, laser additive manufacturing, and laser welding to achieve the effect of improving fatigue resistance and strengthening materials

Active Publication Date: 2018-03-20
SOUTHEAST UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, it is not an effective method to remove the pores of deposited parts due to the large deformation of deposited parts after hot isostatic pressing.

Method used

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  • A surface strengthening method for reducing the porosity of laser additive parts
  • A surface strengthening method for reducing the porosity of laser additive parts
  • A surface strengthening method for reducing the porosity of laser additive parts

Examples

Experimental program
Comparison scheme
Effect test

specific Embodiment 1

[0025] Firstly, X-ray 1 tomographically scans the surface of the part 4 manufactured by laser additive manufacturing, and detects the distribution of pores inside the part. The surface of the part is coated with an absorbing layer 6 and a water-constrained layer 5 is applied by a water-coating robot, and the laser 2 enters a standby mode for laser shock. Input the pore parameters into the industrial computer, and the industrial computer formulates the laser shock strategy according to the distribution and size of the pores:

[0026] When the first air hole 101 is close to the surface (0-1.5mm) and the diameter of the air hole 101 is relatively large (10um-20um), the medium-sized laser energy (10J-15J) is used to shock the surface of the part 4, and the shock wave is A back and forth reflection between the walls of a pore 101 will generate residual compressive stress in the material around the hole wall, preventing the hole wall from becoming a source of cracks.

[0027] When ...

specific Embodiment 2

[0029] Specific embodiment 2: use laser energy 8J, pulse width 22ns, repetition frequency 0.5Hz, spot diameter 6mm, overlap rate 50% of the laser to impact the two sides of the material, and generate pore compression zone CP on both sides of the material.

[0030] Such as Figure 2c , 2d Shown is the change of the pores P in the tensile fracture of the aluminum alloy weld before and after the double-sided laser impact. Figure 2c The middle area I is the impact area, and II is the non-impact area. It can be clearly seen that the pores P are reduced after the impact, and the material structure is refined. The porosity decreased from 2.42% before impact to 0.82%, and the tensile strength increased from 203.98MPa to 237.9MPa.

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Abstract

The invention provides a surface strengthening method capable of reducing the porosity of a laser additive member. The method comprises the following steps: carrying out X-ray computerized tomographic scanning on the surface of a component produced through laser additive manufacturing to detect pore distribution in the component; coating the surface of the component with an absorbing layer, applying a water restraining layer via a water coating robot and allowing the laser to enter Standby (a ready mode) for subsequent laser shock; and inputting pore parameters into an industrial control computer and allowing the industrial control computer to apply different energies, frequencies, power densities and pulse widths onto different laser shock areas according the distribution and sizes of pores. The method can effectively reduce porosity of the laser additive member or the surface layer or sublayer of a laser weld and is capable of refining the crystal grain of a structure and improving the mechanical properties of the member.

Description

technical field [0001] The invention relates to the fields of laser additive manufacturing, laser welding, and laser shock, in particular to a device for improving the strength, fatigue resistance and stress corrosion resistance of laser additive manufactured parts and welded parts through laser shock or ultrasonic shock. The high-pressure shock wave generated by laser shock interacts with the pores and tissues of the surface and subsurface of the material, so that the pores are reduced, closed, and even annihilated, and the structure is refined, and the strength, fatigue resistance and stress corrosion resistance of the component are improved. Background technique [0002] Modern industrial high-end equipment is rapidly developing in the direction of large-scale, high-parameter, high-reliability and long-life service under extremely harsh conditions. The manufacturing technology of high-performance and difficult-to-machine metal large-scale key components is recognized as th...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21D10/00
CPCC21D10/005
Inventor 孙桂芳卢轶王占栋倪中华
Owner SOUTHEAST UNIV
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