Improved Corrosion Resistance of Selective Laser Melted Ti-5Cu Alloy Using Atomized Ti-5Cu Powder

doi:10.1007/s40195-019-00896-1

Abstract

Abstract:

The different types of metal powder used for selective laser melting (SLM) process would cause distinct corrosion behavior due to the uniformity of the obtained microstructure. The SLM-produced Ti-5Cu alloy using atomized Ti-5Cu metal powder (SLMed Ti-5Cu) in this work reveals a relatively uniform microstructure with overwhelming acicular α/α′ phase and shows great advantages on corrosion resistance compared with the SLM-produced Ti-5Cu alloy using the mixture powder (SLMed-M Ti-5Cu). The effect of the micro-galvanic cells decreases due to the undetectable Ti₂Cu phase in the microstructure of the SLMed Ti-5Cu. An apparent passivation behavior was observed for SLMed Ti-5Cu instead of severe pitting phenomenon for the SLMed-M Ti-5Cu. The charge transfer resistance of SLMed Ti-5Cu in this work is 10.09?±?2.63 MΩ cm², which is significantly higher than that of SLMed-M Ti-5Cu (4.76 MΩ cm²). The above result indicates the atomized Ti-5Cu powder plays an important role in the formation of the uniform microstructure of SLMed product, thereby enhancing its corrosion resistance in Hank’s solution at 37 °C.

Key words: Selective laser melting, Corrosion behavior, Uniform microstructure, Ti-5Cu, Passivation, Polarization resistance

Ying Han, Hong-Rui Wang, Yun-Dong Cao, Wen-Tao Hou, Shu-Jun Li. Improved Corrosion Resistance of Selective Laser Melted Ti-5Cu Alloy Using Atomized Ti-5Cu Powder[J]. Acta Metallurgica Sinica (English Letters), 2019, 32(8): 1007-1014.

Figures/Tables 9

Table 1 Main SLM manufacturing parameters used in this work

Parameter	Value
Laser power (W)	200
Laser scan speed (mm s^-1)	1150
Laser spot size (μm)	90
Layer thickness (μm)	30
Hatch space (μm)	100

Fig. 1 XRD pattern for the selective laser melted Ti-5Cu alloy

Fig. 2 Optical microstructure of selective laser melted Ti-5Cu alloy after etching

Fig. 3 Potentiodynamic polarization curves of three parallel samples of the selective laser melted Ti-5Cu alloy immersed in Hank’s solution at 37?±?1 °C

Table 2 Fitting results of potentiodynamic polarization curves for the SLMed Ti-5Cu immersed in Hank’s solution at 37?±?1 °C

Samples	I_pp (μA cm^-2)	E_corr (V)	References
SLMed-M Ti-5Cu	-	-?0.277?±?0.002	[38]
SLMed Ti-5Cu	1.61	-?0.62
	3.15	-?0.69
	3.57	-?0.62
Average	2.78	-?0.64	This work
Standard deviation	1.03	0.04

Fig. 4 Open circuit potential curves of three parallel samples of the selective laser melted Ti-5Cu immersed in Hank’s solution at 37?±?1 °C

Fig. 5 Electrochemical impedance spectra (EIS) results of selective laser melted Ti-5Cu immersed in Hank’s solution at 37?±?1 °C: a Nyquist plots (the inset is the equivalent circuit diagram), b Bode plots (the solid blue arrow indicates the Bode impedance plot and the hollow arrow illustrates the Bode phase angle plot)

Table 3 EIS fitting results for the SLMed Ti-5Cu immersed in Hank’s solution

Samples	R_s (Ω cm²)	CPE?×10⁴ (Ω^-1 cm^-2 S^-ⁿ)	n	R_ct (MΩ cm²)	χ²×10³	References
SLMed-M Ti-5Cu	14.68?±?3.09	13.9?±?0.02	0.97?±?0.01	4.76?±?1.22	-	[38]
SLMed Ti-5Cu	38.38	10.45	0.93	9.01	4.31
	39.51	15.63	0.95	8.16	7.80
	36.98	11.43	0.94	13.10	3.17
Average	38.29	12.50	0.94	10.09	5.09	This work
Standard deviation	1.26	2.75	0.01	2.63	2.41

Fig. 6 Mott-Schottky curves of three parallel samples of selective laser melted Ti-5Cu alloy for the passive film formed at 0.5 VSCE immersed in Hank’s solution at 37?±?1 °C

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