Research Progress on the Crack Formation Mechanism and Cracking-Free Design of γ' Phase Strengthened Nickel-Based Superalloys Fabricated by Selective Laser Melting
ZHU Guoliang,1,2, KONG Decheng1,2, ZHOU Wenzhe1,2, HE Jian1,2, DONG Anping1,2, SHU Da1,2, SUN Baode1,2
1.Shanghai Key Laboratory of Advanced High Temperature Materials and Precision Forming, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
2.State Key Laboratory of Metal Matrix Composite Materials, Shanghai Jiao Tong University, Shanghai 200240, China
Traditional high-strength nickel-based superalloys have a wide solidification temperature range and high proportion of low melting point eutectic phases, which are prone to cracking during rapid nonequilibrium solidification. The residual stress release and rapid nucleation of γ' precipitate during the post-heat treatment process result in crack formation for high-strength nickel-based superalloys, which limits their application and promotion in the field of additive manufacturing. In this review, the research progress in crack formation mechanism and cracking-free design (printing parameter optimization, post-treatment regulation, and alloying design) of high-strength nickel-based superalloys fabricated via additive manufacturing is presented. Additionally, research prospects related to crack control of additively manufactured high-strength nickel-based superalloys are proposed.
ZHU Guoliang, KONG Decheng, ZHOU Wenzhe, HE Jian, DONG Anping, SHU Da, SUN Baode. Research Progress on the Crack Formation Mechanism and Cracking-Free Design of γ' Phase Strengthened Nickel-Based Superalloys Fabricated by Selective Laser Melting[J]. Acta Metallurgica Sinica, 2023, 59(1): 16-30 DOI:10.11900/0412.1961.2022.00434
Fig.3
Atom probe reconstruction from a random high angle grain boundary in the cracked columnar region of a non-weldable nickel-based superalloy with high aluminum and titanium content (a), one-dimensional composition profiles across the γ'/GB/γ interface as denoted by arrow 1 in Fig.3a (b, c) (GB—grain boundary)[29]
Fig.4
Temperature and time relationship of heat treatment cracking of nickel-based superalloys with different precipitate types (t—time) (a)[41], statistics of crack density after 2 h heat-treatment at different temperatures for selective laser melted CM247LC alloy (b)[42], high temperature plasticizing crack at grain boundary (c)[42], and strain-aged crack (d)[42]
Fig.5
Schematic of residual stress distribution and formation mechanism during selective laser melting (HAZ—heat-affected zone) (a), residual stress distribution on the bulk sample before and after removed from the substrate (b)[51]
Fig.6
Relationship between forming quality and scan velocity for CM247LC (a)[55] and scanning strategy for IN738LC (Insets show the corresponding defects such as cracks and voids) (b)[56] fabricated by selective laser melting
Fig.7
Calculated thermal history (temperature profiles, heating and cooling rates) versus time of the same point under the continuous-wave (a) and pulsed-wave modes (b), and the defect of the selective laser melted IN738LC alloys fabricated under the continuous-wave (c) and pulsed-wave mode (d)[57] (Tmax is the maximum temperature of the molten pool, is minimum cooling rate)
Fig.8
Bottom cracking of samples with different sample heights (h) before and after preheating (a)[60], effect of substrate preheating temperature on crack density and residual stress of high-strength nickel-based superalloy (b)[51]
Fig.9
Morphological characteristics of cracks in the additive manufacturing samples before (a) and after (b) hot isostatic pressing[66], distribution of crack defects on the surface of the samples before (c) and after (d) hot isostatic pressing (Inset in Fig.9d shows the locally enlarged view)[55]
Fig.10
Comparisons of cracks (a, b) and elemental distributions at cracks and grain boundaries (c, d) of IN738LC alloy fabricated by selective laser melting before (a, c) and after (b, d) addition of second phase carbides[69] (BD—building direction, LPBF—laser powder bed fusion. Insets in Figs.10a and b show the locally enlarged views)
Additive manufacturing of nickel‐base superalloy René N5 through scanning laser epitaxy (SLE)—Material processing, microstructures, and microhardness properties
A new microsegregation model for rapid solidification multicomponent alloys and its application to single-crystal nickel-base superalloys of laser rapid directional solidification
Numerical simulations are used in this work to investigate aspects of microstructure and microseg-regation during rapid solidification of a Ni-based superalloy in a laser powder bed fusion additive manufacturing process. Thermal modeling by finite element analysis simulates the laser melt pool, with surface temperatures in agreement with thermographic measurements on Inconel 625. Geometric and thermal features of the simulated melt pools are extracted and used in subsequent mesoscale simulations. Solidification in the melt pool is simulated on two length scales. For the multicomponent alloy Inconel 625, microsegregation between dendrite arms is calculated using the Scheil-Gulliver solidification model and DICTRA software. Phase-field simulations, using Ni-Nb as a binary analogue to Inconel 625, produced microstructures with primary cellular/dendritic arm spacings in agreement with measured spacings in experimentally observed microstructures and a lesser extent of microsegregation than predicted by DICTRA simulations. The composition profiles are used to compare thermodynamic driving forces for nucleation against experimentally observed precipitates identified by electron and X-ray diffraction analyses. Our analysis lists the precipitates that may form from FCC phase of enriched interdendritic compositions and compares these against experimentally observed phases from 1 h heat treatments at two temperatures: stress relief at 1143 K (870 °C) or homogenization at 1423 K (1150 °C).
SunX F, SongW, LiangJ J, et al.
Research and development in materials and processes of superalloy fabricated by laser additive manufacturing
The research and development progress of laser additive manufacturing technology in superalloys are summarized in this paper. The technical characteristics and application of additive manufacturing in superalloys, formation mechanism, and the types of microstructure and metallurgical defects are introduced in detail. Moreover, the defect control methods of additive manufacturing of superalloys are summarized from the aspects of laser parameters and composition design, and the direction of laser process parameter optimization and composition optimization is clarified. Finally, the future development trend and research direction of laser additive manufacturing in superalloys are summarized and prospected from the aspects of process optimization and material design.
Nowadays, it is challenging to completely eliminate low angle or high angle grain boundaries (LAGBs or HAGBs) from Nickel-based single crystal (SX) superalloys manufactured using the conventional directional solidification technique. The additions of C, B and Hf have been found to be an effective measure in improving the damage resistance of grain boundary (GB) defects, and thus increasing the creep resistance. However, the strengthening mechanism through their additions is still unclear. In this study, a double-seed solidification technique with two misorientation levels, i.e., 5 degrees and 20 degrees, was used to produce a series of bicrystal superalloys with different contents of Hf and B. It is the first report of an alloy with joint Hf and B addition that demonstrates tolerance to GBs with a misorientation as high as similar to 20 degrees under all of the creep conditions: 1100 degrees C/130 MPa, 980 degrees C/250 MPa and 760 degrees C/785 MPa. Interestingly, the effect of individual additions of Hf or B was not as pronounced as that of the joint Hf and B addition. To understand the influence of these additions on the creep mechanism in nickel-based superalloys with GB defects, a detailed characterization of the microstructures in the vicinity of the LAGBs or HAGBs was carried out, and the elemental distribution at the HAGBs was analyzed with various techniques. This study will be beneficial for understanding the role of Hf and B additions on improving the GB tolerance, and optimizing the Hf and B additions in nickel-based single crystal superalloys. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd.
GrodzkiJ, HartmannN, RettigR, et al.
Effect of B, Zr, and C on hot tearing of a directionally solidified nickel-based superalloy
[J]. Metall. Mater. Trans., 2016, 47A: 2914
KontisP, YusofH A M, PedrazziniS, et al.
On the effect of boron on grain boundary character in a new polycrystalline superalloy
Additive manufacturing of IN100 superalloy through scanning laser epitaxy for turbine engine hot-section component repair: Process development, modeling, microstructural characterization, and process control
[J]. Metall. Mater. Trans., 2015, 46A: 3864
RoyI, BalikciE, IbekweS, et al.
Precipitate growth activation energy requirements in the duplex size γ′ distribution in the superalloy IN738LC
Additive manufacturing of single-crystal superalloy CMSX-4 through scanning laser epitaxy: Computational modeling, experimental process development, and process parameter optimization
We propose a methodology for predicting the printability of an alloy, subject to laser powder bed fusion additive manufacturing. Regions in the process space associated with keyhole formation, balling, and lack of fusion are assumed to be strong functions of the geometry of the melt pool, which in turn is calculated for various combinations of laser power and scan speed via a Finite Element thermal model that incorporates a novel vaporization-based transition from surface to volumetric heating upon keyhole formation. Process maps established from the Finite Element simulations agree with experiments for a Ni-5wt.%Nb alloy and an equiatomic CoCrFeMnNi High Entropy Alloy and suggest a strong effect of chemistry on alloy printability. The printability maps resulting from the use of the simpler Eagar-Tsai model, on the other hand, are found to be in disagreement with experiments due to the oversimplification of this approach. Uncertainties in the printability maps were quantified via Monte Carlo sampling of a multivariate Gaussian Processes surrogate model trained on simulation outputs. The printability maps generated with the proposed method can be used in the selection-and potentially the design-of alloys best suited for Additive Manufacturing. (C) 2019 Published by Elsevier Ltd on behalf of Acta Materialia Inc.
EngeliR.
Selective laser melting & heat treatment of γ′ strengthened Ni-base superalloys for high temperature applications
Inconel 738 LC samples were fabricated using laser powder bed fusion under continuous-wave and pulsed-wave modes. Microstructure, surface quality and mechanical properties were compared to evaluate the printing quality between these 2 laser beam modes. The results show that the application of pulsed wave could effectively eliminate cracking in the as-fabricated sample, despite 0.046% porosity generated. Further microstructure analysis revealed that the refinement of grains by the pulsed-wave laser beam was the main contributor in eliminating the cracks. And this refinement was ascribed to the higher cooling rate under the discontinuous radiation of laser beam proofed by the numerical simulation. And the pore formation was related to Rayleigh instability and residual bubbles in the sample under the pulsed-wave mode, while pores were less detrimental to the mechanical properties than cracks. Therefore, the part under the pulsed-wave mode exhibited superior mechanical performance compared to that under the continuous-wave mode.
ZhangS Y, LinX, WangL L, et al.
Influence of grain inhomogeneity and precipitates on the stress rupture properties of Inconel 718 superalloy fabricated by selective laser melting
Metal additive manufacturing (AM) has garnered tremendous research and industrial interest in recent years; in the field, powder bed fusion (PBF) processing is the most common technique, with selective laser melting (SLM) dominating the landscape followed by electron beam melting (EBM). Through continued process improvements, these methods are now often capable of producing high strength parts with static strengths exceeding their conventionally manufactured counterparts. However, PBF processing also results in large and anisotropic residual stresses (RS) that can severely affect fatigue properties and result in geometric distortion. The dependence of RS formation on processing variables, material properties and part geometry has made it difficult to predict efficiently and has hindered widespread acceptance of AM techniques. Substantial investigations have been conducted with regards to RS in PBF processing, which have illuminated a number of important relationships, yet a review encompassing this information has not been available. In this review, we survey and assemble the knowledge existing in the literature regarding RS in PBF processes. A discussion of background mechanics for RS development in AM is provided along with methods of measurement, highlighting the anisotropic nature of the stress fields. We then review modeling efforts and in-process experimental measurements made to advance process understanding, followed by a thorough analysis and summary of the known relationships of both material properties and processing variables to resulting RS. The current state of knowledge and future research needs for the field are discussed.
KempenK, ThijsL, VranckenB, et al.
Producing crack-free, high density M2 Hss parts by selective laser melting: Pre-heating the baseplate
[A]. Proceedings of the 2013 International Solid Freeform Fabrication Symposium [C]. Austin: University of Texas at Austin, 2013: 131
The effect of hot isostatic pressing and heat treatment on the microstructure and properties of EP741NP nickel alloy manufactured by laser powder bed fusion
Effect of carbon content on the microstructure, tensile properties and cracking susceptibility of IN738 superalloy processed by laser powder bed fusion
Selective laser melting of the hard-to-weld IN738LC superalloy: Efforts to mitigate defects and the resultant microstructural and mechanical properties
Additive manufacturing of nickel‐base superalloy René N5 through scanning laser epitaxy (SLE)—Material processing, microstructures, and microhardness properties
A new microsegregation model for rapid solidification multicomponent alloys and its application to single-crystal nickel-base superalloys of laser rapid directional solidification
... [29]Atom probe reconstruction from a random high angle grain boundary in the cracked columnar region of a non-weldable nickel-based superalloy with high aluminum and titanium content (a), one-dimensional composition profiles across the <i>γ'</i>/GB/<i>γ</i> interface as denoted by arrow 1 in Fig.3a (b, c) (GB—grain boundary)<sup>[<xref ref-type="bibr" rid="R29">29</xref>]</sup>Fig.32.1.3 固态裂纹
Additive manufacturing of IN100 superalloy through scanning laser epitaxy for turbine engine hot-section component repair: Process development, modeling, microstructural characterization, and process control
0
2015
Precipitate growth activation energy requirements in the duplex size γ′ distribution in the superalloy IN738LC
... [41]，选区激光熔化CM247LC合金不同温度热处理2 h后裂纹密度统计，晶界处高温失塑裂纹与应变时效裂纹形貌[42]Temperature and time relationship of heat treatment cracking of nickel-based superalloys with different precipitate types (<i>t</i>—time) (a)<sup>[<xref ref-type="bibr" rid="R41">41</xref>]</sup>, statistics of crack density after 2 h heat-treatment at different temperatures for selective laser melted CM247LC alloy (b)<sup>[<xref ref-type="bibr" rid="R42">42</xref>]</sup>, high temperature plasticizing crack at grain boundary (c)<sup>[<xref ref-type="bibr" rid="R42">42</xref>]</sup>, and strain-aged crack (d)<sup>[<xref ref-type="bibr" rid="R42">42</xref>]</sup>Fig.4
... [41], statistics of crack density after 2 h heat-treatment at different temperatures for selective laser melted CM247LC alloy (b)[42], high temperature plasticizing crack at grain boundary (c)[42], and strain-aged crack (d)[42]Fig.4
... [42]Temperature and time relationship of heat treatment cracking of nickel-based superalloys with different precipitate types (<i>t</i>—time) (a)<sup>[<xref ref-type="bibr" rid="R41">41</xref>]</sup>, statistics of crack density after 2 h heat-treatment at different temperatures for selective laser melted CM247LC alloy (b)<sup>[<xref ref-type="bibr" rid="R42">42</xref>]</sup>, high temperature plasticizing crack at grain boundary (c)<sup>[<xref ref-type="bibr" rid="R42">42</xref>]</sup>, and strain-aged crack (d)<sup>[<xref ref-type="bibr" rid="R42">42</xref>]</sup>Fig.4
Additive manufacturing of single-crystal superalloy CMSX-4 through scanning laser epitaxy: Computational modeling, experimental process development, and process parameter optimization
... [51]Schematic of residual stress distribution and formation mechanism during selective laser melting (HAZ—heat-affected zone) (a), residual stress distribution on the bulk sample before and after removed from the substrate (b)<sup>[<xref ref-type="bibr" rid="R51">51</xref>]</sup>Fig.5<strong>3</strong> 裂纹消除方法与抗裂纹合金设计
... [51]Bottom cracking of samples with different sample heights (<i>h</i>) before and after preheating (a)<sup>[<xref ref-type="bibr" rid="R60">60</xref>]</sup>, effect of substrate preheating temperature on crack density and residual stress of high-strength nickel-based superalloy (b)<sup>[<xref ref-type="bibr" rid="R51">51</xref>]</sup>Fig.83.1.3 热等静压处理
... [55,56]Relationship between forming quality and scan velocity for CM247LC (a)<sup>[<xref ref-type="bibr" rid="R55">55</xref>]</sup> and scanning strategy for IN738LC (Insets show the corresponding defects such as cracks and voids) (b)<sup>[<xref ref-type="bibr" rid="R56">56</xref>]</sup> fabricated by selective laser meltingFig.6
... [55] and scanning strategy for IN738LC (Insets show the corresponding defects such as cracks and voids) (b)[56] fabricated by selective laser meltingFig.6
... 热等静压(hot isostatic pressure，HIP)作为常用的激光增材制造样件后处理技术，被广泛应用于闭合高温合金内部气孔以及裂纹过程[62~64].热等静压处理的基本原理是以气体或液体作为压力介质，材料在加热过程中经受各向均衡的压力，在高温与高压的共同作用下促进材料致密化和元素扩散[65].经过热等静压处理后，增材制造金属的熔池边界消失，树枝晶发生溶解并形成等轴晶.Sentyurina等[66]分别针对激光增材制造技术制备的哈氏合金以及EP741NP合金进行了热等静压处理，发现合金中的裂纹以及气孔在热等静压过程中得到闭合，如图9a和b[66]，但是其力学性能尤其是强度发生下降.同时，有研究[67]发现Rene88DT合金经过热等静压处理后的闭合裂纹，在进行固溶和时效热处理之后重新出现.研究证实，这些裂纹是由于γ'相的溶解以及在固溶热处理的冷却阶段细小的γ'相再析出导致的，这说明热等静压工艺不能够完全解决打印过程中出现的裂纹问题.热等静压前后增材制造样品内部裂纹的形貌特征<sup>[<xref ref-type="bibr" rid="R66">66</xref>]</sup>以及样品表面的裂纹缺陷分布情况<sup>[<xref ref-type="bibr" rid="R55">55</xref>]</sup>Morphological characteristics of cracks in the additive manufacturing samples before (a) and after (b) hot isostatic pressing<sup>[<xref ref-type="bibr" rid="R66">66</xref>]</sup>, distribution of crack defects on the surface of the samples before (c) and after (d) hot isostatic pressing (Inset in Fig.9d shows the locally enlarged view)<sup>[<xref ref-type="bibr" rid="R55">55</xref>]</sup>Fig.9
... ,56]Relationship between forming quality and scan velocity for CM247LC (a)<sup>[<xref ref-type="bibr" rid="R55">55</xref>]</sup> and scanning strategy for IN738LC (Insets show the corresponding defects such as cracks and voids) (b)<sup>[<xref ref-type="bibr" rid="R56">56</xref>]</sup> fabricated by selective laser meltingFig.6
... [57]Calculated thermal history (temperature profiles, heating and cooling rates) versus time of the same point under the continuous-wave (a) and pulsed-wave modes (b), and the defect of the selective laser melted IN738LC alloys fabricated under the continuous-wave (c) and pulsed-wave mode (d)<sup>[<xref ref-type="bibr" rid="R57">57</xref>]</sup> (<i>T</i><sub>max</sub> is the maximum temperature of the molten pool, <span class="formulaText"><inline-formula><math id="M1"><msub><mrow><mfenced close="|" open="" separators="|"><mrow><mfrac><mrow><mi mathvariant="normal">d</mi><mi>T</mi></mrow><mrow><mi mathvariant="normal">d</mi><mi>t</mi></mrow></mfrac></mrow></mfenced></mrow><mrow><mi mathvariant="normal">m</mi><mi mathvariant="normal">i</mi><mi mathvariant="normal">n</mi></mrow></msub></math></span></inline-formula></span> is minimum cooling rate)Fig.73.1.2 基板预热
... [60]，基板预热温度对高强镍基高温合金裂纹密度及残余应力的影响规律[51]Bottom cracking of samples with different sample heights (<i>h</i>) before and after preheating (a)<sup>[<xref ref-type="bibr" rid="R60">60</xref>]</sup>, effect of substrate preheating temperature on crack density and residual stress of high-strength nickel-based superalloy (b)<sup>[<xref ref-type="bibr" rid="R51">51</xref>]</sup>Fig.83.1.3 热等静压处理
... [60], effect of substrate preheating temperature on crack density and residual stress of high-strength nickel-based superalloy (b)[51]Fig.83.1.3 热等静压处理
The effect of hot isostatic pressing and heat treatment on the microstructure and properties of EP741NP nickel alloy manufactured by laser powder bed fusion
... [66]以及样品表面的裂纹缺陷分布情况[55]Morphological characteristics of cracks in the additive manufacturing samples before (a) and after (b) hot isostatic pressing<sup>[<xref ref-type="bibr" rid="R66">66</xref>]</sup>, distribution of crack defects on the surface of the samples before (c) and after (d) hot isostatic pressing (Inset in Fig.9d shows the locally enlarged view)<sup>[<xref ref-type="bibr" rid="R55">55</xref>]</sup>Fig.9
... [66], distribution of crack defects on the surface of the samples before (c) and after (d) hot isostatic pressing (Inset in Fig.9d shows the locally enlarged view)[55]Fig.9
... [69]Comparisons of cracks (a, b) and elemental distributions at cracks and grain boundaries (c, d) of IN738LC alloy fabricated by selective laser melting before (a, c) and after (b, d) addition of second phase carbides<sup>[<xref ref-type="bibr" rid="R69">69</xref>]</sup> (BD—building direction, LPBF—laser powder bed fusion. Insets in Figs.10a and b show the locally enlarged views)Fig.103.2.2 合金成分设计
Effect of carbon content on the microstructure, tensile properties and cracking susceptibility of IN738 superalloy processed by laser powder bed fusion
Selective laser melting of the hard-to-weld IN738LC superalloy: Efforts to mitigate defects and the resultant microstructural and mechanical properties
图1
