Browsing by Author "Sun, Yongle"
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Item Open Access Assessing and mitigating the distortion and stress during electron beam welding of a large shell-flange structure(Elsevier, 2022-08-30) Sun, Yongle; Smith, Mike; Dutilleul, Thomas; Jones, SteveElectron beam (EB) welding can efficiently join large-scale components using one single autogenous pass, but it still faces challenges associated with weld-induced distortion and stress. This study investigates EB welding in a low-alloy steel thick-section shell-flange structure for a small modular reactor. A 3D thermal-metallurgical-mechanical model is developed to assess the weld-induced distortion and stress, as well as the strategy to mitigate them. When no restraint is imposed on the circumferential weld plane, an opening and sliding gap develops during the EB welding, which can cause weld defects and even process failure. Restraint through tack welds can effectively mitigate the gapping distortion, but it generates high transient tensile stress in the tack weld. Circumferentially continuous tack weld is preferential over circumferentially discrete tack welds to minimise the tensile stress. The final residual stress is insensitive to the tack-weld restraint, and the stress distribution in the steady-state welding region is broadly similar to that found in plate butt welds. However, concentration of residual stresses with high triaxiality occurs in the weld stop region, with high tensile stresses generated just behind the beam stop location, which cannot be diminished by overlap welding or change of weld stop position. The mechanisms responsible for the distortion and the transient and residual stresses are analysed. This study could provide rational basis for designing weld restraint to control distortion and guiding stress mitigation strategy for crack-susceptible region in EB weldments.Item Open Access Computationally efficient models of high pressure rolling for wire arc additively manufactured components(MDPI, 2021-01-04) Gornyakov, Valeriy; Sun, Yongle; Ding, Jialuo; Williams, StewartHigh pressure multi-layer rolling is an effective method to reduce residual stress and distortion in metallic components built by wire arc additive manufacturing (WAAM). However, the mechanisms of the reduction in residual stress and distortion during multi-layer rolling are not well understood. Conventional finite element models for rolling are highly inefficient, hindering the simulation of multi-layer rolling for large WAAM components. This study aims to identify the most suitable modelling technique for finite element analysis of large WAAM component rolling. Four efficient rolling models were developed, and their efficiency and accuracy were compared with reference to a conventional large-scale rolling model (i.e., control model) for a WAAM built wall. A short-length transient model with fewer elements than the control model was developed to reduce computational time. Accurate predictions of stress and strain and a reduction in computational time by 96.5% were achieved using the short-length model when an implicit method for numerical solution was employed, while similar efficiency but less accurate prediction was obtained when an explicit solution method was adopted. A Eulerian steady-state model was also developed, which was slightly less efficient (95.91% reduction in computational time) but was much less accurate due to unrealistic representation of rolling process. The applicability of a 2D rolling model was also examined and it was found that the 2D model is highly efficient (99.52% time reduction) but less predictive due to the 2D simplification. This study also shows that the rigid roller adopted in the models is beneficial for improving efficiency without sacrificing accuracyItem Open Access Crystal plasticity constitutive model and thermodynamics informed creep-fatigue life prediction model for Ni-based single crystal superalloy(Elsevier, 2023-07-23) Lu, Pin; Jin, Xiaochao; Li, Pan; Sun, Yongle; Fan, XuelingNi-based single crystal superalloys are the main constituent materials for aeroengine turbine blades. They are subjected to extensive in-service plastic deformation and creep-fatigue interaction, which can cause damage and failure and hence limit the turbine blade durability. In this study, a novel crystal plasticity-based constitutive model is proposed to predict the cyclic inelastic deformation of Ni-based single crystal superalloy under creep-fatigue loads, and the key aspects examined include cyclic strain hardening, ratcheting and stress relaxation behavior. The novelty of the model lies in the introduction of a dislocation density parameter in the kinematic hardening rule to describe the evolutionary characteristics of hysteresis loops. The constitutive model is implemented via the crystal plasticity finite element method and the predictions are in good agreement with experimental results. Furthermore, thermodynamic entropy generation is innovatively adopted as an indicator parameter for analysis of Ni-based single crystal creep-fatigue failure, and the corresponding creep and fatigue damage models are developed to evaluate the degree of damage. The half-life concept associated with the steady-state hysteresis loop is employed in the failure model to predict the creep-fatigue life without being limited by the computational efficiency of the crystal plasticity finite element method. The proposed model can well capture the characteristics of Ni-based single crystal creep-fatigue life, and the prediction falls within a scatter band of factor 2.0 compared to experimental results. The proposed creep-fatigue life prediction model is underpinned by deformation and failure mechanisms, which would provide a basis for accurate analysis and robust assessment of Ni-based single crystal superalloy performance and life.Item Open Access Data supporting: 'Assessing and mitigating the distortion and stress during electron beam welding of a large shell-flange structure'(Cranfield University, 2022-08-31 15:56) Sun, Yongle; Smith, Mike; Dutilleul, Thomas; Jones, SteveFig. 7. (c) temperature histories on the outer surface points (i.e., Out1 and Out2) and inner surface points (i.e., In1 and In2). Fig. 8. (d) The cross-weld line profile of hardness distribution. Fig. l10. Evolution of the opening (a) and sliding (b) displacements for mid-thickness ocations on the weld plane with different angular distances to the EB weld start position.Item Open Access Data supporting: 'Modelling and optimising hybrid process of wire arc additive manufacturing and high-pressure rolling'(Cranfield University, 2022-10-04 10:54) Gornyakov, Valeriy; Sun, Yongle; Ding, Jialuo; Williams, StewartFigure 7 Predicted distortion of the WAAM part after deactivation of clamps . Figure 8 Longitudinal RS distributions along the vertical path in the symmetry plane for the full-length mechanical models after clamps deactivation, compared to experimental measurements [5]. The flat roller (a) and slotted roller (b) were used in the rolling simulations, and the full-length model was based on the solution mapped from the steady-state region of the reduced-length WAAM + IL rolling model Figure 10 Concurrent evolution of temperature and longitudinal stress (a), as well as the longitudinal PS (b), in the layer 6 during WAAM deposition of layers 6-8 in conjunction with IL rolling using the flat roller. The data were collected at the top of layer 6 in the inspection plane and the rolling phases are highlighted in the yellow shaded areas. Figure 11 Concurrent evolution of temperature and longitudinal stress (a), as well as longitudinal PS (b), in the layer 6 during WAAM deposition of layers 9-11 in conjunction with IL rolling using the flat roller. The data were collected at the top of layer 6 in the inspection plane and the rolling phases are highlighted in the yellow shaded areas. Figure 12 Concurrent evolution of temperature and longitudinal stress (a), as well as longitudinal PS (b), in the layer 6 during WAAM deposition of layers 12-14 in conjunction with IL rolling using the flat roller. The data were collected at the top of layer 6 in the inspection plane and the rolling phases are highlighted in the yellow shaded areas. Figure 13 Concurrent evolution of the longitudinal PS and stress in the layer 9 during WAAM deposition of layers 9-16 in conjunction with IL rolling using the slotted roller. The data were collected at the top of layer 9 in the inspection plane (the slotted roller started rolling on layer 6) and the rolling phases are highlighted in the yellow shaded areas. Figure 18 Evolution of longitudinal PS in the layer 6 during WAAM deposition and stacked 4L rolling with flat roller. The rolling phases are highlighted in the yellow shaded areas.Item Open Access Data: Thermo-Capillary-Gravity Bidirectional Modelling for Evaluation and Design of Wire-Based Directed Energy Deposition Additive Manufacturing(Cranfield University, 2023-10-31 11:08) Mosalman Haghighi, Alireza; Ding, Jialuo; Sun, Yongle; Wang, Chong; Williams, StewartIn this study, a thermo-capillary-gravity bidirectional analytical model is developed based on the fundamental governing physics, enabling fast predictions of both w-DED bead geometries and process parameters. A novel method is also proposed to determine the power transfer efficiency and wire melting efficiency defined in the model. In the forward modelling, deposit bead geometries, such as layer height and width, can be predicted for given process parameters and material properties. In the reverse modelling, the outputs of the model are process parameters, including heat source power and travel speed, to achieve the deposit bead geometries as required for a given application. This bidirectional modelling approach is applicable to different w-DED processes, and it has been validated for the deposition of steel walls using plasma transferred arc and cold wire gas metal arc processes. The developed bidirectional analytical model could be used as an efficient and reliable tool for w-DED process evaluation and design.Item Open Access Dataset for Computationally Efficient Models of High Pressure Rolling for Wire Arc Additively Manufactured Components(Cranfield University, 2021-01-04 13:51) Gornyakov, Valeriy; Sun, Yongle; Ding, Jialuo; Williams, Stewart1. Dataset for Figure 5: Equivalent plastic strain obtained along centreline on the top of the WAAM wall.2. Dataset for Figure 6: Reaction forces obtained at the rotation point of the rollers (note that only half of the WAAM component was considered in the models).3. Dataset for Figure 13: Longitudinal PS distributions on inspection planes.4. Dataset for Figure 14: Longitudinal RS distributions on inspection planes.Item Open Access Dataset for Efficient determination and evaluation of steady-state thermal-mechanical variables generated by wire arc additive manufacturing and high pressure rolling(Cranfield University, 2021-11-04 09:14) Gornyakov, Valeriy; Sun, Yongle; Ding, Jialuo; Williams, Stewart1. Dataset for Figure 5: Temperature histories predicted by the short thermal WAAM model at the thermocouple locations: (a) TP1, (b) TP2, (c) TP3 and (d) TP4. The experimental measurements by Ding [34] are also included for comparison.2. Dataset for Figure 11: Longitudinal RS distributions along the Z-direction (through wall height, see Figure 10b for the path of the line plots) in the mapped long mechanical model before and after clamps removal for the WAAM component. The experimental measurements by Ding et al. [34] and Colegrove et al. [5] are also included, which were conducted using neutron diffraction after clamps removal.3. Dataset for Figure 12: Verification of out-of-plane distortion predicted by the mapped long mechanical model after clamps removal. Note that the experimental measurement by Ding [34] using a 3D laser scanner was based on a four-layer deposited wall, and the WAAM model was adapted accordingly.Item Open Access Dataset for Understanding and designing post-build rolling for mitigation of residual stress and distortion in wire arc additively manufactured components(Cranfield University, 2022-01-10 08:55) Gornyakov, Valeriy; Ding, Jialuo; Sun, Yongle; Williams, StewartDataset for Figure 9 Influence of friction coefficient on longitudinal PS in the WAAM built component after rolling: a) flat roller, b) profiled roller, and c) slotted roller (F = 50 kN). Dataset for Figure 10 Vertical penetration of slotted roller for different friction coefficients (F = 50 kN). Dataset for Figure 11 Influence of friction coefficient on longitudinal RS distributions in the WAAM built component after rolling with a) flat roller, b) profiled roller and c) slotted roller (F = 50 kN). Dataset for Figure 13 Influence of rolling load on longitudinal PS in the WAAM component after rolling: a) flat roller, b) profiled roller, and c) slotted roller (µ = 0.1). Dataset for Figure 15 Influence of rolling load on the longitudinal RS in the WAAM component after rolling: a) flat roller, b) profiled roller, and c) slotted roller (µ = 0.1). Dataset for Figure 16 Influence of roller design on mitigation of the compressive longitudinal PS caused by WAAM deposition. The rolling loads are a) 25 kN, b) 50 kN and c) 75 kN (µ = 0.1). Dataset for Figure 17 Influence of roller design on mitigation of the tensile longitudinal RS caused by WAAM deposition. The rolling loads are a) 25 kN, b) 50 kN, and c) 75 kN (µ = 0.1). Dataset for Figure 19 Influence of the post-build rolling using the flat roller on the WAAM deposition RS obtained by the long mechanical model before and after clamps removal (F = 50 kN and µ = 0.1). Dataset for Figure 20 Comparison of vertical distortion in as-built and post-build rolled full-length WAAM component after removal of clamps (flat roller, F = 50 kN and µ = 0.1). Dataset for Figure 21 Comparison of vertical distortion in long WAAM components after post-build rolling with flat, profiled and slotted rollers at rolling loads of a) 25 kN, b) 50 kN, and c) 75 kN (µ = 0.1). Dataset for Figure 22 Comparison in a) PS and b) RS predictions between flat roller models with and without consideration of the WAAM deposition before rolling simulation (µ = 0.5).Item Open Access Effects of dilution on the hardness and residual stresses in multipass steel weldments(Elsevier, 2020-07-18) Sun, Yongle; Hamelin, Cory J.; Vasileiou, Anastasia N.; Xiong, Q.; Flint, Thomas F.; Obasi, Gideon C.; Francis, John A.; Smith, Mathew C.A thermal-metallurgical-mechanical model was developed to study the effects of dilution in each weld pass for multipass gas tungsten arc and submerged arc welding in low alloy steel (i.e. SA508) plates. Hardness distributions and residual stresses were measured on the transverse sections perpendicular to the welding direction of the manufactured weldments. The predicted hardness and residual stresses were compared with the measurement data and shown to be reasonably accurate. The results showed that dilution can significantly affect both the hardness and the residual stress field in the weld metal. It was found that, for the base and filler materials used, increased dilution led to greater weld-metal hardness and reduced the magnitude of tensile stress or promoted compressive stress in the as-deposited and reheated weld metals. This mechanical behaviour is associated with the tendency for diluted weld metal to experience delayed austenite decomposition, owing to the high hardenability of SA508 steel relative to the filler materials used. Although dilution is irrelevant for the hardness of the base material and its transformation products adjacent to the weld metal, it affected the full-field residual stresses via the equilibrium interaction between the stresses in the base and weld metalsItem Open Access Effects of roughness on stresses in an oxide scale formed on a superalloy substrate(MDPI, 2021-04-19) Zhao, Yang; Sun, Fan; Jiang, Peng; Sun, YongleThe effects of surface roughness on the stresses in an alumina scale formed on a Fecralloy substrate are investigated. Spherical indenters were used to create indents with different radii and depths to represent surface roughness and then the roughness effect was studied comprehensively. It was found that the residual stresses in the alumina scale formed around the rough surface are almost constant and they are dominated by the curvature rather than the depth of the roughness. Oxidation changes the surface roughness. The edge of the indent was sharpened after oxidation and the residual stress there was released presumably due to cracking. The residual stresses in the alumina scale decrease with increase in oxidation time, while the substrate thickness has little effect, given that the substrate is thicker than the alumina scale. Furthermore, the effect of roughness on the oxide growth stress is analysed. This work indicates that the surface roughness should be considered for evaluation of stresses in coatings.Item Open Access Efficient determination and evaluation of steady-state thermal-mechanical variables generated by wire arc additive manufacturing and high pressure rolling(IOP, 2021-11-02) Gornyakov, Valeriy; Sun, Yongle; Ding, Jialuo; Williams, StewartWire arc additive manufacturing (WAAM) of large component is susceptible to residual stress (RS) and distortion, which are detrimental and need to be mitigated through high pressure rolling or other methods. In this study, an efficient modelling approach is developed to simulate both WAAM and rolling, and this approach can also be applied to other manufacturing processes to determine steady-state variables. For a clamped wall component, the computationally efficient reduced-size WAAM and rolling models (i.e. short models) can obtain steady-state solutions equivalent to those obtained by conventional full-size models. In the short models, the undesirable effect of reducing the length of the modelled component is counteracted by imposing additional longitudinal constraint as proper to specific processes. The steady-state solution obtained by the short model in clamped condition is then mapped to a long model for analysis of RS and distortion after removal of clamps. The WAAM model predictions of temperature, RS and distortion are in good agreement with experimental measurements. For the steady-state region in the WAAM deposited wall, compressive longitudinal plastic strain (PS) is approximately uniformly formed, and the influential factors and implications of the PS are analysed. The high pressure rolling on the wall after WAAM deposition introduces tensile PS that compensates for the compressive PS induced by the WAAM deposition, thereby mitigating the tensile RS in the clamped wall and alleviating the bending distortion after the removal of clamps. This study demonstrates an efficient approach for modelling large-scale manufacturing and provides insights into the steady-state strains and stresses generated by WAAM and rolling.Item Open Access Efficient modelling and evaluation of rolling for mitigation of residual stress and distortion in wire arc additive manufacturing.(Cranfield University, 2021-08) Gornyakov, Valeriy; Ding, Jialuo; Sun, YongleWire and Arc Additive Manufacturing (WAAM) is a promising technology for manufacturing large-scale parts with low costs and short lead time. One of the main challenges in applying WAAM in industry is the effective control of residual stress and distortion. It has been found that high-pressure inter-layer rolling can effectively mitigate the residual stress and distortion of WAAM components. However, the mechanism behind the mitigation efficacy is of a complex nature and has not been well understood. Finite element analysis (FEA) has proven to be a reliable and accurate method for simulating the thermo-mechanical process. The FEA simulation of large-scale inter-layer rolling is challenging due to the high computational cost and complicated coupling between WAAM and rolling. This research is based on efficient models for simulating WAAM deposition and rolling processes, and their combination for large-scale structures. The efficient modelling method is developed using a reduced-size model to determine the steady-state solution, and then mapping the solution to a full-size structure for further analysis. This method is successfully applied to study the evolution of residual stress and plastic strain during the post-build and inter-layer rolling of WAAM deposited walls. The numerical predictions are verified with experimental results. Cyclic formation of tensile residual stress occurs during the WAAM deposition, whereas inter-layer rolling counteracts the development of the residual stress. The effectiveness of roller designs is studied for reducing residual stress of the WAAM process. Compared with a flat roller, a slotted roller can induce greater longitudinal plastic strains and more effectively reduce the tensile residual stress in the WAAM wall. Removal of the clamps only results in a slight redistribution of residual stress in the post-build and inter-layer rolled WAAM components, since the rolling mitigates most of the tensile residual stresses caused by WAAM. To enhance the manufacturing efficiency, stacked-layers rolling can replace inter- layer rolling for RS and distortion mitigation in tall WAAM parts. Influences of main process parameters, such as rolling load and roller-to-component friction, on mitigation of RS and distortion are also studied. Finally, based on the understanding gained through the simulations, recommendation of an optimal rolling strategy is made for future industrial application.Item Open Access Efficient reduced-order thermal modelling of scanning laser melting for additive manufacturing(Elsevier, 2023-10-02) Chen, Guangyu; Ding, Jialuo; Sun, Yongle; Chen, Xin; Wang, Chong; Rodrigues Pardal, Goncalo; Williams, StewartAdditive manufacturing (AM) with a scanning laser (SL) to independently control melt pool shape has the potential to achieve part building with high geometric accuracy and complexity. An innovative dynamic convection boundary (DCB) method is proposed to develop a reduced-order finite element (FE) model to accelerate the thermal analysis of a SL process for AM. The DCB method approximates the thermal conduction of the adjacent material around the bead region by using a convection boundary condition that can be dynamically adjusted during the numerical solution. Thereby, a smaller problem domain and fewer elements are involved in the reduced-order FE modelling. A non-oscillating equivalent bar-shaped heat source was also introduced as a simplified substitution for a high oscillation frequency SL heat source. The DCB-based reduced-order thermal model achieved over 99% accuracy compared to the full-scale model but reduced the element amount by 73% and the computational time by 58%. The use of the bar-shaped equivalent heat source can further enhance computational efficiency without compromising the prediction accuracy of a high oscillation frequency SL process. The DCB-based reduced-order thermal modelling method and equivalent heat source could be adopted to boost extensive parametric analysis and optimisation for novel AM processes. Study on large structures AM could also be facilitated by simplifying the computation at critical regions. This study can also enable efficient thermal analyses of different manufacturing processes, such as welding, cladding, and marking.Item Open Access Efficient reduced-order thermal modelling of scanning laser melting for additive manufacturing.(Cranfield University, 2023-09-25 16:20) Chen, Guangyu; Ding, Jialuo; Sun, Yongle; Chen, Xin; Wang, Chong; Rodrigues Pardal, Goncalo; Williams, StewartThermal videos show the dynamic changing of the scanning laser melt pools with different oscillation frequenciesItem Open Access Fabrication and characterisation of high-performance joints made of ZrB2-SiC ultra-high temperature ceramics(Elsevier, 2021-08-16) Jin, Xiaochao; Yang, Jingjing; Sun, Yongle; Li, Pan; Hou, Cheng; Zhao, Yuxiang; Fan, XuelingJoining is crucial for ultra-high temperature ceramics (UHTCs) to be used in demanding environments due to the difficulty in manufacturing large and complex ceramic components. In this study, ZrB2-SiC composite UHTCs parts were joined via Ni foil as filler, and the mechanical properties and oxidation behaviour of the fabricated ZrB2-SiC/Ni/ZrB2-SiC (ZS/Ni/ZS) joint were investigated. Firstly, dense ZrB2-SiC composites were prepared from nano-sized powders by spark plasma sintering (SPS). The ZrB2-SiC parts were then joined using SPS. Furthermore, the elastic modulus, hardness, shear strength and high temperature oxidation behaviour of the ZS/Ni/ZS joint were examined to evaluate its properties and performance. The experimental results showed that the ZrB2-SiC parts were effectively joined via Ni foil using SPS and the resultant microstructures were free from any marked defects or residual metallic layers in the joint. Although the elastic modulus and hardness in the joining zone were lower than those in the base ZrB2-SiC ceramics, the shear strength of the joint reached ∼161 MPa, demonstrating satisfactory mechanical properties. Oxidation tests revealed that the ZS/Ni/ZS joint possesses good oxidation resistance for a wide range of elevated temperatures (800–1600 oC), paving the way for its employment in extreme environments.Item Open Access Inhomogeneous microstructure and fatigue crack propagation of thick-section high strength steel joint welded using double-sided hybrid fiber laser-arc welding(Elsevier, 2020-10-13) Feng, Jiecai; Li, Liqun; Chen, Yanbin; Tian, Yingzhong; Sun, Yongle; Zhang, Xuanjun; Zhang, JieThe inhomogeneous microstructure and fatigue crack propagation of 30 mm thick-section high strength steel welded joint by double-sided hybrid fiber laser-arc welding were investigated in detail. The results indicated that the average effective grain size of the laser zone was only 1/2 of that of the arc zone, due to the faster cooling rate of the laser resource. The base metal consisted of massive polygonal ferrites and small granular carbides, while fine grained region, the coarse grained region and weld metal were all composed of martensite with a high dislocation density. Compared with the arc zone, the percentage of grain boundaries with high misorientation angle increased 24% for the laser zone, as the average grain size of the laser zone was smaller than that of the arc zone. The results also revealed that the fatigue crack propagation resistance of the welded joint was higher than that of the base metal. Meanwhile, a significant increase in the fatigue crack propagation resistance of the laser zone occurred, as compared with the arc zone, due to the refined grains and the high proportion of the grain boundaries with high misorientation angle (>15°) in the laser zone.Item Open Access Knowledge-based bidirectional thermal variable modelling for directed energy deposition additive manufacturing(Informa UK Limited, 2024-09-05) Qin, Jian; Taraphdar, Pradeeptta; Sun, Yongle; Wainwright, James; Lai, Wai Jun; Feng, Shuo; Ding, Jialuo; Williams, StewartDirected energy deposition additive manufacturing (DED-AM) has gained significant interest in producing large-scale metallic structural components. In this paper, a knowledge-based machine learning (ML) approach, combining both physics-based simulation and data-driven modelling, is proposed for a study on thermal variables of DED-AM. This approach enables both forward and backward predictions, which breaks down the barriers between the basic process parameters and key process attributes. Process knowledge plays a critical role to enable the prediction and enhance the accuracy in both prediction directions. The proposed ML approach successfully predicted the thermal variables of wire arc based DED-AM for forward modelling and the process parameters for backward modelling, typically within 7% errors. This approach can be further generalised as a powerful modelling tool for design, control, and evaluation of DED-AM processes regarding build geometry and properties, as well as an essential constituent element in a digital twin of a DED-AM system.Item Open Access Local residual stress evolution of highly irregular thermally grown oxide layer in thermal barrier coatings(Elsevier, 2020-12-25) Jiang, Peng; Yang, Liuyu; Sun, Yongle; Li, Dingjun; Wang, TiejunLocal residual stress in thermally grown oxide (TGO) layers is the primary cause of failure of thermal barrier coating (TBC) systems, especially TBCs prepared by air plasma spray (APS) with a highly irregular TGO. Herein, the distribution of residual stress and the evolution of the irregular TGO layer in APS TBCs were investigated as a function of oxidation time. The stress was measured from cross-sectional micrographs and converted to the actual stress inside the coatings before sectioning. The TGO exhibited significant inhomogeneity at different locations. Stress conversion occurred across the TGO thickness; the layer near the yttria-stabilised zirconia (YSZ) component exhibited compressive stress, whereas that along the bond coat was under tensile stress. The evolution of the compressive stress is also discussed. These analyses may provide a better understanding of the mechanism of APS TBCs.Item Open Access Mitigation of platinum depletion in platinum diffused single phase bond coat on CMSX-4 superalloy(MDPI, 2021-05-31) Bai, Mingwen; Chen, Ying; Sun, Yongle; Xiao, PingPt-diffused bond coat with a mixture of γ/γ’ phase has just been developed in the recent decades as a cheaper alternative to the Pt-enriched β-phase Aluminide bond coat that contains a higher content of Al. However, concerns are raised on the inevitable depletion of Pt near the coating interface that may endanger the component after long-term service. In this study, modified Pt-diffused bond coats with a single phase (γ or γ’) were made by applying selective etching on CMSX-4 single crystal superalloys prior to the electroplating of Pt. The single-phase bond coats show distinctive diffusion behaviour in comparison with the conventional γ/γ’ bond coat. Surprisingly, Pt remains more stable in the γ’-phase bond coat with significantly less depletion after diffusion, which implies a potential in saving a considerable amount of Pt. On the other hand, however, the depletion of Pt is more severe in the γ-phase bond coat. The mechanism that governs the diffusion behavior of Pt in the γ and γ’-phase was also discussed that mainly concerns with thermodynamic and kinetic factors.