Understanding the microstructural evolution of cold sprayed Ti-6Al-4V coatings on Ti-6Al-4V substrates

Lek, Jun Yan; Bhowmik, Ayan; Tan, Adrian Wei-Yee; Sun, Wenfeng; Song, Xu; Zhai, Wei; Buenconsejo, Pio John S.; Li, Feng; Liu, Erjia; Lam, Yeng Ming; Boothroyd, Chris

doi:10.1016/j.apsusc.2018.07.175

Cited by 56 publications

(28 citation statements)

References 57 publications

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“…The overview of the impact is shown in Figure 12 with the evolutions of the elements A, B and C in terms of temperature, stress and strain at 30 ns upon impact. At 30 ns, these regions undergo a clear jump (termed "secondary" jump) in their temperature profiles, where the adiabatic shear instability takes place and aids in interfacial bonding [12], as reported in a previous work [61]. For the case of 730 m/s, the top section of the particle is relatively colder (ranging from 750 to 900 K) as compared to the interface (900 to 1400 K).…”

Section: Finite Element Modelsupporting

confidence: 62%

“…The Johnson-Cook plasticity model was used to determine the effects of strain hardening, strain rate hardening and thermal softening on the equivalent plastic deformation resistance. This model has been widely used to simulate the jetting phenomenon of particle impact during cold spraying [12,14,18,27,34,[57][58][59][60][61][62][63][64][65][66][67][68], despite its limitation at very high strain rates [57,69,70]. The equivalent plastic stress of the material is given as follows:…”

Section: Finite Element Modellingmentioning

confidence: 99%

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Influence of Particle Velocity When Propelled Using N2 or N2-He Mixed Gas on the Properties of Cold-Sprayed Ti6Al4V Coatings

et al. 2018

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Cold-spraying is a relatively new low-temperature coating technology which produces coatings by the deposition of metallic micro-particles at supersonic speed onto target substrate surfaces. This technology has the potential to enhance or restore damaged parts made of light metal alloys, such as Ti6Al4V (Ti64). Particle deposition velocity is one of the most crucial parameters for achieving high-quality coatings because it is the main driving force for particle bonding and coating formation. In this work, studies were conducted on the evolution of the properties of cold-sprayed Ti64 coatings deposited on Ti64 substrates with particle velocities ranging from 730 to 855 m/s using pure N2 and N2-He mixture as the propellant gases. It was observed that the increase in particle velocity significantly reduced the porosity level from about 11 to 1.6% due to greater densification. The coatings’ hardness was also improved with increased particle velocity due to the intensified grain refinement within the particles. Interestingly, despite the significant differences in the coating porosities, all the coatings deposited within the velocity range (below and above critical velocity) achieved a high adhesion strength exceeding 60 MPa. The fractography also showed changes in the degree of dimple fractures on the particles across the deposition velocities. Finite element modelling was carried out to understand the deformation behaviour of the impacting particles and the evolutions of strain and temperature in the formed coatings during the spraying process. This work also showed that the N2-He gas mixture was a cost-effective propellant gas (up to 3-times cheaper than pure He) to deliver the high-quality Ti64 coatings.

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Section: Finite Element Modelsupporting

confidence: 62%

Section: Finite Element Modellingmentioning

confidence: 99%

Influence of Particle Velocity When Propelled Using N2 or N2-He Mixed Gas on the Properties of Cold-Sprayed Ti6Al4V Coatings

et al. 2018

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“…9. The obvious strong peaks at about 35.5°, 38.9°, 40.6°, and 78.6° in the patterns confirmed that the Ti6Al4V samples mainly contain the hexagonal close packed (HCP) α-Ti, our lab-based GIXRD facility was not able to recognize the peaks of the body centered cubic (BCC) β-Ti [48][49][50]. Furthermore, it is quite obvious that the intensities and positions of the diffraction peaks for all samples were similar.…”

Section: Methodsmentioning

confidence: 85%

Large current ion beam polishing and characterization of mechanically finished titanium alloy (Ti6Al4V) surface

Zhou

et al. 2019

Applied Surface Science

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Ti6Al4V samples with a surface roughness of about 0.2 μm were polished by a high fluence ion beam source, and influences of the ion current, energy and incident angle on the surface roughness of Ti6Al4V were studied. The as-polished surfaces were characterized by laser scanning confocal microscopy (LSCM), atomic force microscopy (AFM), grazing incidence X-ray diffraction (GIXRD) and X-ray photoelectron spectroscopy (XPS). The LSCM images revealed that the density of pits in the original surface decreased greatly after the ion polishing process. In addition, the surface roughness calculated from these images proved that the mean value reduced to 53 nm with an ion energy, current and incident angle of 600 eV, 130 mA and 75°, respectively. The smoothing effect was also confirmed by the power spectral density (PSD) functions calculated from the AFM data. GIXRD patterns indicated that the Ti6Al4V samples mainly contain the hexagonal close packed (HCP) α-Ti, no recognizable peaks corresponding to the body centered cubic (BCC) β-Ti were observed. Furthermore, after the ion beam polishing process, the phase of all the as-polished samples kept steady. The XPS results revealed that C, O, Ti, Al and V were present in both the original as well as the polished samples. In addition, due to the highly reactive characteristics of Ti, Al and V elements, a higher signal for oxygen can also be observed on the outermost surface of the ion beam polished samples. The polishing process of Ti6Al4V surface bombarded by Ar ion beam is also simulated by binary collision approximation (BCA) code SDTrimSP, the effects of ion beam energy and incident angle on the sputtering yield were investigated. The results showed that the sputtering yield of Ti, Al and V atoms increased almost linearly with the ion energy. However, as for the influence of ion incident angle, the sputtering yield first increased gradually from 0° and peaked at about 65°, then decreased rapidly because the incident angle is too large for Ar ion to penetrate into the surface of Ti6Al4V sample.

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“…Therefore, the schematic of the early stage of intermetallics formation in Fig. 8 (e) assumes that Ni 3 Ti and Ti 2 Ni form on Ni and Ti side of the interface (Ref 32 , 45 , 59 , 60 ) and NiTi phase nucleates at the interface of these two phases with some delay (Fig. 8 (f)).…”

Section: Resultsmentioning

confidence: 99%

Intermetallic Phase Evolution of Cold-Sprayed Ni-Ti Composite Coatings: Influence of As-Sprayed Chemical Composition

2020

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Owing to low-temperature deposition conditions and high deposition rate, cold spray offers unique advantages in manufacturing a wide variety of metallic and composite coatings including metal matrix composites produced from physically blended powders. One of the challenges of producing composite coatings using cold spray is the deviation of coatings composition from the blended feedstock powder composition. This is of utmost importance as it affects the composition and phase evolution of intermetallic forming coatings during post spray heat treatment. In this work, cold spray of composite Ni - Ti coatings and formation of intermetallics from post spray heat treatment were investigated as a first step to examine the potential of producing equiatomic bulk Ni - Ti by cold spray. Three different physically blended Ni and Ti powders mixtures were sprayed on titanium substrates to address the coating composition variation from the blended feedstock powder and study its influence on phase evolution during post spray heat treatment. High-density and well-dispersed composite coatings were achieved for each case. EDS analysis revealed as-sprayed coatings with 10.5, 35.9 and 56.9 at.% Ni (and with balanced Ti ratios) from the three powder mixtures. Annealing treatments were conducted at 400, 500 and 900 °C for 1 and 2 h and comparative studies of the intermetallic compound formations were carried out. Microstructural investigation showed that all three equilibrium intermetallics phases of binary Ni - Ti phase diagram (Ni 3 Ti, Ti 2 Ni and NiTi) formed in the two Ni-rich composite coatings with NiTi phase being maximum in the coating with the closest composition to equiatomic ratio while only Ti 2 Ni phase formed in the Ti-rich coating after annealing. Thermal etching analysis of coatings showed that NiTi phase forms with a gradient microstructure from Ti splats boundary toward the center of splats, which is attributed to the grain refinement of CS samples at splat boundary and intermetallic nucleation mechanism.

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Understanding the microstructural evolution of cold sprayed Ti-6Al-4V coatings on Ti-6Al-4V substrates

Cited by 56 publications

References 57 publications

Influence of Particle Velocity When Propelled Using N2 or N2-He Mixed Gas on the Properties of Cold-Sprayed Ti6Al4V Coatings

Influence of Particle Velocity When Propelled Using N2 or N2-He Mixed Gas on the Properties of Cold-Sprayed Ti6Al4V Coatings

Large current ion beam polishing and characterization of mechanically finished titanium alloy (Ti6Al4V) surface

Intermetallic Phase Evolution of Cold-Sprayed Ni-Ti Composite Coatings: Influence of As-Sprayed Chemical Composition

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