Abstrakcyjny
Aluminum alloy casing parts are prone to defects such as porosity and cracks during manufacturing and service, leading to part scrapping and resource waste. This study focuses on ZL105A aluminum alloy aerospace parts, using laser cladding technology to repair the porosity formed during service using AlSi10Mg powder. By adjusting process parameters and performing metallographic analysis, the porosity of the cladding layer under different conditions was evaluated. The optimal process parameters were identified as: laser power 1.6~1.8 kW, powder feeding speed 0.6 r/min, argon gas flow 4 L/min, scan spacing 1.2 mm, and scanning speed 600 mm/min. After repair, the part’s density reached 98.18%.

Wprowadzenie
With the development of metal additive manufacturing technologies, laser cladding has become an important method for repairing part defects. However, aluminum alloys are characterized by low laser absorption, high thermal conductivity, and susceptibility to oxidation, which, along with the complex structure and thin-wall features of casing parts, make repair difficult. Based on actual production needs, this study explores laser cladding repair technology for aluminum alloy casings, providing technical support for the remanufacturing of key aerospace components.

Current Research on Laser Cladding Technology

Domestic Research
Laser cladding technology research in China began in the 1990s, focusing mainly on process parameter optimization, cladding material performance, and equipment development. For example, Liu Xiubo et al. studied the impact of scanning speed on the microstructure and hardness of the cladding layer. Wu Hongliang et al. used Ni-based alloys to laser clad the surface of TA2 titanium alloy, significantly increasing its hardness. Wang et al. conducted a systematic study of the Ti2Ni3Si/Ni3Ti cladding layer’s properties. Domestic companies, such as Xi’an Bishi and Bolite, are actively developing laser cladding equipment. However, current equipment typically operates at 3000~6000 W with limited cladding depth.

International Research
Research on laser cladding began earlier abroad, covering material performance and equipment development. For instance, Ignat et al. analyzed the relationship between dilution rate and process parameters. Bernabe et al. used Al-Si powder to clad magnesium alloys, achieving high hardness and corrosion-resistant coatings. Ocelik et al. improved friction properties by laser cladding TiB2/Ti-6Al-4V. Companies abroad, such as Lasermach in Belgium and Nittany Laser in the USA, have developed equipment for laser cladding on internal surfaces, with power ranging from 2000 to 6000 W and maximum processing depths of up to 500 mm.

Experimental Methods

Equipment and Materials
The experiments were conducted using an LDM8060 laser directed energy deposition system, equipped with a coaxial powder feeding system, a five-axis workbench, and an argon gas protection system. The cladding material used was AlSi10Mg powder, prepared by atomization, with a particle size range of 53-105 μm, ensuring good weldability.

Process Parameter Design
Several sets of process parameters were compared (see Table 1), and Group B and Group C parameters were selected for further verification:

Fixture Design
A specialized fixture was designed to repair internal holes in casing parts, using the part’s lower holes and parallel surfaces for fixation. The fixture had a maximum laser spot shift of 1.5 mm during rotation, which slightly affected the cladding quality.

Results and Discussion

Cladding Layer Quality Analysis
Using metallographic analysis and ImageJ software to statistically determine the porosity, the results are as follows:

Group B Parameters: Average melt pool depth of 181.73 μm, average number of pores 274.67, with 98.58% of pores having a diameter ≤ 50 μm.

Group C Parameters: Average melt pool depth of 961.63 μm, average number of pores 188.67, with 98.18% of pores having a diameter ≤ 50 μm.

Under Group C parameters, the melt pool is deeper, with significantly fewer pores, making it more suitable for repairing deep hole defects.

Actual Part Repair Test
Cladding tests were carried out under argon gas protection (oxygen content <200 ppm) and in air. The cladding layer under argon protection was more uniform and dense, while pre-aggregated particles appeared in air cladding. After the repair, cutting was performed, but misalignment in centering resulted in uneven cutting of the cladding layer, indicating that fixture alignment precision needs improvement.

Wniosek
Through process parameter optimization, the optimal parameters for repairing ZL105A aluminum alloy casings were identified as: laser power 1.6~1.8 kW, powder feeding speed 0.6 r/min, argon gas flow 4 L/min, scan spacing 1.2 mm, and scanning speed 600 mm/min.

The cladding layer under argon protection exhibited superior quality, but at a higher cost.

Air cladding, although more efficient and cost-effective, resulted in a less uniform layer.

In actual repairs, fixture centering accuracy must be ensured to guarantee cladding layer integrity and processing quality.