Hot Corrosion Resistance of TB8 Titanium Alloy after ECAP and Heat Treatment

Abstract

The metastable β titanium alloy TB8 (Ti-12.76Mo-2.13Nb-2.73A1-0.16Si) was used as the original material, and the secondary processing method combining equal channel angular pressing (ECAP) and heat treatment was adopted. With the help of optical microscope (OM), scanning electron microscope (SEM) and X-ray diffractometer (XRD), the corrosion behavior of TB8 titanium alloy after different secondary processing (800 °C/850 °C solid solution-520°C aging, ECAP-800 °C/850 °C solid solution-520 °C aging, and 800 °C/850 °C solid solution-ECAP-520 °C aging) was studied. The experimental results show that the hot corrosion products of the six samples are similar, mainly Na₂Si₂O₅, MoS₂, TiCl₂, Ti(SO₄)₂, and TiS. Due to the grains of the TB8 titanium alloy treated by 850 °C solid solution-ECAP-520 °C aging are obviously refined, the surface structure is the most smooth and dense, forming a continuous Al₂O₃ protective film, and the surface defects are the least after corrosion. Its corrosion layer thickness is the lowest (102.3 µm), only 36.5%–81.4% of that of other secondary processing titanium alloys. In addition, the corrosion kinetics curves of the six materials all follow parabolic laws, and the minimum corrosion weight gain of the samples after 850 °C solution-ECAP-520 °C aging treatment is 0.7507 mg·mm⁻², showing better hot corrosion resistance.

Keywords

TB8 / ECAP / heat treatment / hot corrosion resistance

References

[1] Chen Y, Yang W, Bo A, et al. Underlying Burning Resistant Mechanisms for Titanium Alloy[J]. Materials & Design, 2018, 156: 588-595.

[2] Paranthaman V, Dhinakaran V, Sai MS, et al. A Systematic Review of Fatigue Behaviour of Laser Welding Titanium Alloys[J]. Materials Today: Proceedings, 2021, 39: 520-523.

[3] Jin J, Zhou S, Zhao Y, et al. Refined Microstructure and Enhanced Wear Resistance of Titanium Matrix Composites Produced by Selective Laser Melting[J]. Optics & Laser Technology, 2021, 134: 106 644.

[4] Delbari SA, Namini AS, Asl MS. Hybrid Ti Matrix Composites with Tib₂ and TiC Compounds[J]. Materials Today Communications, 2019, 20: 100 576.

[5] Shi Y, Joseph S, Saunders EA, et al. Agcl-Induced Hot Salt Stress Corrosion Cracking in a Titanium Alloy[J]. Corrosion Science, 2021, 187: 109 407.

[6] Joseph S, Lindley TC, Dye D, et al. The Mechanisms of Hot Salt Stress Corrosion Cracking in Titanium Alloy Ti-6Al-2Sn-4Zr-6Mo[J]. Corrosion Science, 2018, 134: 169-178.

[7] Myers JR, Hall JA. Hot-salt stress-corrosion Cracking of Titanium Alloys: an Improved Model for the Mechanism[J]. Corrosion, 1977, 33: 252-257.

[8] ALL AAK BPB High Temperature Oxidation Resistance and Microstructure of Laser-Shock Peened Ti-beta-21S[J]. Surface and Coatings Technology, 2020, 403: 126 368.

[9] Hu YM, Floer W, Krupp U, et al. Microstructurally Short Fatigue Crack Initiation and Growth in Ti-6.8Mo-4.5Fe-1.5Al[J]. Materials Science and Engineering: A, 2000, 278: 170-180.

[10] Yumak N, Aslantas K. A Review on Heat Treatment Efficiency in Metastable β Titanium Alloys: The Role of Treatment Process and Parameters[J]. Journal of Materials Research and Technology, 2020, 9: 15360-15380.

[11] Agarwal KM, Tyagi RK, Singhal A, et al. Effect of ECAP on the Mechanical Properties of Titanium and Its Alloys for Biomedical Applications[J]. Materials Science for Energy Technologies, 2020, 3: 921-927.

[12] Chuvil’deev VN, Kopylov VI, Nokhrin AV, et al. Effect of Severe Plastic Deformation Realized by Rotary Swaging on the Mechanical Properties and Corrosion Resistance of Near-α-titanium Alloy Ti-2.5Al-2.6Zr[J]. Journal of Alloys and Compounds, 2019, 785: 1233-1244.

[13] Chuvil”Deev VN, Kopylov VI, Nokhrin AV, et al. Study of Mechanical Properties and Corrosive Resistance of Ultrafine-grained α-titanium Alloy Ti-5Al-2V[J]. Journal of Alloys and Compounds, 2017, 723: 354-367.

[14] Agarwal KM, Tyagi RK, Choubey V, et al. Enhancements of Mechanical Properties of Materials Through ECAP for High Temperature Applications[J]. Materials Today:Proceedings, 2021, 46: 6490-6495.

[15] Segal VM. Materials Processing by Simple Shear[J]. Materials Science and Engineering: A, 1995, 197: 157-164.

[16] Zhang ZJ, Son IH, Im YT, et al. Finite Element Analysis of Plastic Deformation of CP-Ti by Multi-Pass Equal Channel Angular Extrusion at Medium Hot-Working Temperature[J]. Materials Science and Engineering: A, 2007, 447: 134-141.

[17] Yilmaz Y, Demiroren H, Tong SY. An Approximation to Determine Corrosion And Mechanical Behavior of Ti-Based Alloys[J]. Surface Review and Letters, 2021, 28: 1-10.

[18] Marino CEB, Oliveira EMD, Rochafilho RC. On the Stability of Thin-Anodic-Oxide Films of Titanium in Acid Phosphoric Media[J]. Corrosion Science, 2001, 43: 1465-1476.

[19] Chen JR, Tsai WT. In situ Corrosion Monitoring of Ti-6Al-4V Alloy in H2SO4/HCl Mixed Solution Using Electrochemical AFM[J]. Electrochimica Acta, 2011, 56: 1746-1751.

[20] Ettefagh AH, Zeng C, Guo S, et al. Corrosion Behavior of Additively Manufactured Ti-6Al-4V Parts and the Effect of Post Annealing[J]. Additive Manufacturing, 2019, 28: 2-258.