Effect of laser process parameters on the pores, surface roughness, and hardness of laser selective melting of dental cobalt-chrome alloys

doi:10.7518/hxkq.2024.2023400

Abstract

Abstract:

Objective To address the quality problems caused by high porosity in the preparation of dental cobalt-chrome alloy prosthetics based on selective laser melting (SLM) technology, we investigated the influence mechanism of different forming process parameters on the microstructure and properties of the materials. Moreover, the range of forming process parameters that can effectively reduce defects was precisely defined. Methods The effects of laser power, scanning speed, and scanning distance on the pore properties, surface roughness, and hardness of dental cobalt-chrome alloy were investigated by adjusting the printing parameters in the process of SLM. Through metallographic analysis, image analysis, and molten pool simulation, the pore formation mechanism was revealed, and the relationship between the porosity and energy density of SLM dental cobalt-chrome alloy was elucidated. Results When the linear energy density was higher than 0.18 J/mm, the porosity defect easily appeared at the bottom of the molten pool. When the laser energy density was lower than 0.13 J/mm, defects occurred in the gap of the molten pool due to insufficient melting of powder. In particular, when the linear energy density exceeded the threshold of 0.30 J/mm or was below 0.12 J/mm, the porosity increased significantly to more than 1%. In addition, we observed a negative correlation between free surface roughness and energy density and an inverse relationship between macroscopic hardness and porosity. Conclusion On the basis of the conditions of raw materials and molding equipment used in this study, the key process parameters of SLM of molding parts with porosity lower than 1% were successfully determined. Specifically, these key parameters included the line energy density, which ranged from 0.13 J/mm to 0.30 J/mm, and the scan spacing should be strictly controlled below 90 μm.

Key words: selective laser melting, oral prosthesis, dental cobalt-chrome alloy

CLC Number:

R783.2

Sang Lei, Yan Jiazhen, Li Ning, Xin Chenglai, Wang Qun, Liu Chang. Effect of laser process parameters on the pores, surface roughness, and hardness of laser selective melting of dental cobalt-chrome alloys[J]. West China Journal of Stomatology, 2024, 42(4): 462-469.

Figures/Tables 8

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References 21

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组别	激光功率/W	扫描速度/（mm/s）	扫描间距/μm	线能量密度/（J/mm）	体能量密度/（J/mm3）
1	200	1 100	70	0.182	86.6
2	170	1 100	70	0.155	73.6
3	140	1 100	70	0.127	60.6
4	110	1 100	70	0.100	47.6
5	170	500	70	0.340	161.9
6	170	600	70	0.283	134.9
7	170	700	70	0.243	115.7
8	170	800	70	0.213	101.2
9	170	1 100	70	0.155	73.6
10	170	1 400	70	0.121	57.8
11	170	1 600	70	0.106	50.6
12	170	1 800	70	0.094	45.0
13	170	1 100	30	0.155	171.7
14	170	1 100	40	0.155	128.8
15	170	1 100	50	0.155	103.0
16	170	1 100	70	0.155	73.6
17	170	1 100	90	0.155	57.2
18	170	1 100	110	0.155	46.8
19	170	1 100	130	0.155	39.6

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