Research On Corrosion Behavior Of Typical Materials Manufactured By Selective Laser Melting

As one of the most promising technologies of additive manufacturing,Selective Laser Melting（SLM）technology has extensive applications in industry.It can manufacture complex structure and precision parts to solve the difficulties in traditional processing methods.However,there are some obvious differences in microstructure and properties between the parts manufactured by SLM and traditional methods.And corrosion resistance property is a significant factor to consider for metal parts in the service process.But few researches focus on the corrosion resistance of SLMed parts,which limits the engineering applications of this technology.This paper carries out a study on corrosion resistance of two typical SLMed samples of TC4 and IN718 alloy.Firstly,the corrosion behaviors of different densities of TC4alloy samples,which manufactured by changing the SLM process parameters,are tested in 3.5%NaCl solution by electrochemical method.Secondly,corrosion behaviors of TC4alloy samples in different surface states,which created through changing the inclined angle,are tested in different corrosion environments.Finally,the microstructure and corrosion resistance of IN718 specimens,which manufactured by using the optimized SLM process parameters,are studied after different heat treatments.The main conclusions are as follows.The density of the SLMed TC4 sample is the highest and the corrosion resistance is the best when the scanning spacing is 0.12 mm.As the scanning spacing increasing,the corrosion resistance increases at first and then decreases.The effect of slicing thickness on the corrosion behavior exhibits directionality,and the corrosion behavior of XOY plane is not changed with slicing thickness.While the corrosion behavior of XOZ plane increases at first and then decreases as slicing thickness increasing,and the optimal corrosion resistance is obtained at the slicing thickness of 40μm.The corrosion resistance of SLMed TC4 alloy using the optimized process parameters is better than traditional rolled TC4 alloy in 3.5%NaCl solution.Pitting is the main corrosion failure mode for SLMed TC4 samples.The corrosion behavior of TC4 alloy is related to the type and size of constituent phases in microstructure.The inclined angle will change the surface state of the SLMed samples.The surface roughness of the sample fabricated at an inclined angle of 0°has the smallest value of5.1μm,and the surface roughness of the sample fabricated at an inclined angle of 45°has the maximum value of 22.5μm.The corrosion law of SLMed TC4 samples with different surface state in solutions of 3.5%NaCl,3.5%NaOH and 1 mol/L H₂SO4 are corresponding.That is the corrosion resistance of samples at 0°is the best,90°forming samples take second place and are better than the samples formed at 30°and 60°,and the formed samples at 45°have the worst corrosion resistance.For formed TC4 samples with the same surface state,the sequence of corrosion resistance in the three representative acidic solutions is H₂SO₄>HCl>HF+HNO₃.The corrosion resistance of SLMed IN718 alloy is better than those of traditional rolling and heat treated.After solution treatment under 1000℃,the SLMed IN718 alloy has the fastest corrosion rate in corrosives compared with other solution treatment.The corrosion rate of the samples after solution and aging is the fastest and the corrosion resistance is the worst,while the self-corrosion current density of the samples after aging is the highest,and its passivation layer is the most vulnerable.