Microstructure and Performance of NiTi-Based Intermetallic Compound Coatings by Laser Melting Deposition

Fig. 1. Microstructure of NiTi-based intermetallic compound coating. (a) Cross-section of coating; (b) bottom of coating; (c) magnified image of Fig. 1(b); (d) middle of coating; (e) magnified image of Fig. 1(d); (f) top of coating; (g) magnified image of Fig. 1(f)

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Fig. 2. XRD result of NiTi-based intermetallic compound coating

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Fig. 3. Phase diagrams of Ni-Ti alloy under different temperatures[16]

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Fig. 4. Microhardness distribution of NiTi-based intermetallic compound coating

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Fig. 5. Morphology of indentation under a load of 1.96 N. (a) Interface between substrate and coating; (b) magnified image

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Fig. 6. Potentiodynamic curves

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Fig. 7. EIS results of NiTi-based intermetallic compound coating and TC4 alloy. (a) Nyquist plot; (b)(c) Bode plots; (d) equivalent circuit

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Fig. 8. Morphologies after electrochemical corrosion. (a) NiTi-based intermetallic compound coating; (b) TC4 alloy

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Table 1. Chemical compositions of TC4 powder (mass fraction,%)
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Table 1. Chemical compositions of TC4 powder (mass fraction,%)
Element C H O N Fe Al V Ti
Content 0.08 0.015 0.2 0.05 0.4 6.05 4.02 Bal.

Table 2. EDS analysis of microstructure of NiTi-based intermetallic compound coating
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Table 2. EDS analysis of microstructure of NiTi-based intermetallic compound coating
Location Mass fraction /%
Al Ti Cr Ni
1 2.98 58.60 4.20 34.22
2 3.93 57.11 5.79 33.17
3 2.73 57.62 4.75 34.90
4 2.08 62.30 5.75 29.87
5 1.61 39.60 15.37 43.41
6 3.45 38.14 7.34 51.08
7 6.84 26.30 3.58 63.28
8 1.13 31.62 17.45 49.80

Table 3. Polarization parameters of NiTi-based intermetallic compound coating
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Table 3. Polarization parameters of NiTi-based intermetallic compound coating
Sample i_corr /(10^-6 A·cm^-2) E_corr /V E_pp /V
TC4 alloy 2.068 -0.943 1.116
Composite coating 55.41 -0.799 2.240

Table 4. Electrochemical parameters obtained from equivalent circuit fitting
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Table 4. Electrochemical parameters obtained from equivalent circuit fitting
Sample R_s /(Ω·cm²) R_t /(10² Ω·cm²) R_ct /(10⁴ Ω·cm²) Z_CPE /(10^-5 Ω^-1·cm²·sⁿ) C_d1 /(10^-5 μF·cm^-2) n
TC4 14.82 2.459×10³ 13.33 4.28 3.274 0.864
Coating 15.80 2.636 3.901 19.95 7.183 0.658

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Xiaoqin Dai, Quanju Shi, Yu Zhao, Yongbo Xu, Jianbo Lei, Shengfeng Zhou. Microstructure and Performance of NiTi-Based Intermetallic Compound Coatings by Laser Melting Deposition[J]. Chinese Journal of Lasers, 2018, 45(7): 0702008

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