Alloy CMSX-4 Research Articles

Dynamic steady-state tertiary creep in a Nickel-base single crystal superalloy at high temperatures

Nickel-base single crystal (SX) blades, oriented along the [0 0 1] crystallographic direction, were introduced for gas turbine engines in 1980 [1, 2]. Creep resistance of SX materials is derived from the large volume fraction, about 70%, of ordered cubical γ ′ precipitates in a disordered γ matrix. Since the γ /γ ′ morphology changes during creep, considerable attention has been paid to this topic [1, 3]. Because SX materials exhibit high stress sensitivity and large elongation, the increase in stress, due to the reduction in the cross-sectional area during creep, must control the strain rate and the time to rupture for constant load tests. The objective of this letter is to present our study on this subject. Both experimental and analytical techniques presented here are applicable in general to other materials exhibiting high ductility. The “third generation” CMSX-10 with a nominal composition (wt.%) of 2Cr, 3Co, 0.4Mo, 6Re, 5W, 5.7Al, 0.2Ti, 8Ta, 0.1Nb, 0.03Hf, balance Ni [2] was used. Creep specimens, with a nominal diameter of 4.0 mm and a uniform gauge section of 25 mm, were prepared from fully heat-treated [0 0 1]-oriented bars. The γ ′ precipitates had average edge dimensions of about 0.5 μm and there were rows of spherical pores, up to 25 μm in diameter, aligned parallel to the growth direction. Six constant load tests, for an initial stress σ i of 700 MPa, were performed in air at 1073 to 1273 K (800– 1000◦C) ± 1 K using a single lever dead-load system, a three-zone furnace and an extensometer. Out of these six tests, two rupture tests were performed first at 1123 K and 1173 K to determine the fracture times and strains (19% and 18% at 1123 K and 1173 K respectively). Four strain relaxation (creep) and recovery tests (SRRT) [4] for relaxation times, trlx required to reach a total strain of 15% (close to fracture), were then performed at 1073 K, 1148 K, 1223 K and 1273 K. SRRT involves the application of the load as rapidly as possible, deforming a specimen for trlx, and then removing the load fully and rapidly, but keep monitoring the strain for a long time until no further strain recovery is noticed. SRRTs allow determination of elastic, delayed elastic and viscous components of strain as functions of trlx. Only the strain relaxation results of these tests will be presented and discussed here. Fig. 1 shows all the strain relaxation curves. The average value of the bulk Young’s modulus, E = 110 GPa, obtained from the initial elastic strain, ee, agreed with the expected range for the [0 0 1]-orientation at these temperatures [3, 5]. This allowed the estimation of creep strain, ec (= e − ee), where e is the total strain. The high stress of 700 MPa, equivalent to 6.4 × 10−3 E, was chosen to avoid complexities of γ ′ rafting [6, 7]. The fracture strains for the two tests bear strong similarities with those of the “second generation” alloy CMSX-4 for lower stresses, 130 to 400 MPa, at 1273 K [7]. Assuming incompressibility during creep, the actual stress, σA was estimated from σA = σ i (1 + ec). This gives, for example, the fracture stress, σAf of 833 MPa for the test at 1123 K. It would be appropriate to mention here that the specimen cross-sectional shape after the tests was found to be slightly elliptical. For example, the majorand the minor-axis of the specimen tested at 1148 K was 3.76 mm and 3.70 mm respectively near the middle of the specimen – giving a small but measurable eccentricity of 0.183. This does not necessarily mean asymmetry in the load axis and, in fact, is expected due to a number of active slip systems in cubic materials, as reported for SX alloy SRR99 in [8]. Fig. 2 shows the strain rate-time, e − t and σA − t curves for the test at 1223 K (950 ◦C). It shows that e changes with time in a complex manner similar to observations in CMSX-4 [9, 10]. However, the monotonically increasing σA suggests that the conventional approach of plotting eec curves for analytical purposes (assuming constant stress) violates the basic principles of experimental physics. The relationship between e and σA for the results in Fig. 2 and plotted in Fig. 3 clearly shows that the ‘tertiary’ or the ’time-wise accelerating’ stage represents a “stresswise dynamic steady state” (broken line in Fig. 3). Note the high regression coefficient, R2 of 0.997. Similar observations were also made at other temperatures (Fig. 4). The test at 1173 K shows some inconsistency due to some

Measurement of the density and surface tension of Ni-based superalloys in the liquid and mushy states

The densities of three Ni-based superalloys have been measured in both liquid and mushy states by both a modified sessile drop method (MSDM) and a modified pycnometric method (MPM) for alloys CMSX-4 and CM186LC, and for CMSX-10 alloy by MSDM only. The surface tensions of liquid CMSX-4, CM186LC, and CMSX-10 superalloys were measured using the sessile drop method. All measurements were carried out in a highly purified argon atmosphere with the oxygen partial pressure of less than 10−19 MPa in the gas outlet. The densities of all superalloys in both liquid and mushy states were found to decrease with increasing temperature. The volume thermal expansion of each superalloy in the mushy state was found to be higher than that in the liquid state. The densities determined by different methods have been critically assessed and recommended values in both liquid and mushy states are given as a linear function of temperature for the three Ni-based superalloys. The surface tension of liquid CMSX-4 superalloy was found to decrease with increasing temperature, while that of liquid CMSX-10 superalloy increases with increasing temperature. The wetting behavior of liquid CM186LC on the alumina substrate was found (1) to differ significantly from that of CMSX-4 and CMSX-10 and (2) to vary with time. A HfO2-rich layer was found in the contact area of CM186LC with the alumina substrate, which could lead to some uncertainty in the value obtained for the surface tension determined for CM186LC.

Simulation of the solidification of CMSX-4

The solidification and cooling of the nickel–base alloy CMSX-4 during casting was simulated using a one-dimensional model for diffusion-controlled phase transformations. A temperature interval from the liquidus temperature to 800 K is covered, including solid state transformations. This paper discusses several results: fraction solid compared to results from Scheil and equilibrium calculations, microsegregation profiles for Al, Co, Cr, Re, Ta, Ti and W compared to experimental values, and the formation of finely dispersed γ ′ -phase in the solid state. The relatively simple one-dimensional diffusion simulation is shown to be a valuable tool to investigate phase formation and microsegregation during solidification and cooling. In the case of CMSX-4 it represents a significant improvement over the commonly used Scheil calculations for the prediction of the fraction solid.

The effect of TCP morphology on the development of aluminide coated superalloys

Aluminisation gives a cost-effective coating for turbine components subjected to hostile environments. However, inter-diffusion between coating and substrate causes changes in microstructure, which destroy the creep resistance of the alloy. We compare low-temperature, high-activity aluminide and platinum-modified aluminide coatings on the single crystal, nickel-based alloys, RR3000, CMSX-4 and TMS75, and describe the evolution of the microstructure following exposure at 1100 °C. In particular, the precipitation of topologically close packed (TCP) phases varies with alloy composition. We suggest that the morphology of the precipitates may influence the rate of ingress of the coating into the substrate. For example, the alloy RR3000 forms the σ-phase, which has an excellent fit with the alloy {1 1 1} planes and can nucleate as very fine small precipitates. In contrast, the μ-phase formed in the alloy CMSX-4 forms much larger, more widely spaced, TCP phases which necessitate a longer diffusion path for the slow diffusing refractory elements of which they are principally composed.

ＣＭＳＸ４のクリープ強度におよぼす時効熱処理の影響

In single crystals of Ni-based superalloys, the γ' precipitate size has been shown to affect both the tensile strength and the creep behavior at intermediate temperatures. The microstructure of Ni-based superalloys contains primary cuboidal γ' particles that precipitate during aging treatment, and cooling γ' particles that precipitate during cooling from the aging temperature. In the Ni-based superalloy containing a high volume fraction of γ' precipitates, the change in the morphology of the secondary γ' precipitates in a matrix channel has been found to affect the creep strength. In this study, three kinds of aged specimens were prepared to investigate the influence of the morphology of γ' precipitates on the strengths of CMSX4 alloy. Slow furnace cooling from the aging temperature was employed to obtain a clean matrix channel completely devoid of secondary γ' precipitates. In order to clarify the effect of secondary γ' precipitates, the strengths of the furnace-cooled specimens were compared with those of the forced-airquenched specimens containing numerous superfine γ' precipitates in the matrix channel, and those of the standard two-step-aged specimens. The purpose of the present investigation is to gain a better understanding of the effect of precipitation heat treatment on the material strengths at an intermediate temperature, where the secondary γ' precipitates remain undissolved during creep deformation.

Microstructural instability in coated single crystal superalloys

Specimens of CMSX-4 and CMSX-10 alloys have been platinum aluminised to give a single phase (Ni,Pt)Al coating and a two phase PtAl2–(Ni,Pt)Al coating, respectively. Specimens of the coated alloys were exposed in an oxidising environment for 188, 350 and 750h at a temperature of 1100°C. Specimens were then sectioned, polished and examined using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS) and X-ray diffraction (XRD). Decreases in nickel activity and increases in aluminium activity occurred within the substrate close to the coating/alloy interface. These effects resulted in precipitation of additional γ′ in the alloy, which caused rafting of the γ′ and encapsulation of needle-like sigma phase in γ′. The development of these needle-like sigma phases beneath the diffusion layer in the CMSX-10 alloy at 1100°C is significant, such that they extend to a depth of 0.2mm. In addition, they cause failure at the coating/substrate interface in the case of the CMSX-10 alloy. For the CMSX-4 alloy, equilibration effects remote from the coating cause further precipitation of sigma phases in isolated cells in γ′ regions. The implications of these instabilities on superalloy properties are discussed.

Surface tension of nickel based superalloy CMSX-4

The surface tension, γ, of CMSX-4 alloy was measured in a flow of purified argon gas by the sessile-drop technique over the temperature range 1670-1926K. The surface tension at the liquidus temperature (1648 K) is 1970 mNm - 1 and its temperature coefficient, dγ/dT, is -1.38 mN m - 1 K - 1 . The surface tension was also calculated from thermodynamic data on the basis of Butler's model. The calculated value of 1776 ′ 50 mN m - 1 is in agreement with the measured one within the expected error limits.

Lattice misfit in CMSX4-like nickel-base superalloys and its temperature dependence

Abstract The temperature dependence of the γ – γ′ lattice misfit (δ) between precipitates and matrix in three modified CMSX4-type nickel-base superalloys was investigated. The effect of the so-called standard heat treatment and of the addition of elements like Nb, Ti and Re on δ was also monitored. The misfit was measured by in situ high-resolution X-ray diffraction (up to 1375 K), and the microstructure was investigated by means of optical and transmission electron microscopy. It was found that with the addition of Nb the microstructure becomes more sensitive to thermal treatments, while the presence of Ti strongly influences the lattice misfit δ. Re also influences the value of δ, but in combination with other elements. A standard CMSX4 alloy shows relatively less influence of the thermal treatments on the misfit values and the microstructural properties. For all samples investigated, the misfit is negative at all temperatures.

The effect of material behaviour on the analysis of single crystal turbine blades: Part I - Material model

This paper describes a slip system model developed for the analysis of modern single crystal superalloys - specifically, the first generation alloys RR2000 and SRR99, and the second generation alloy CMSX-4. The single crystal model is implemented as an ABAQUS User MATerial (UMAT) subroutine, the framework is based on the classical theory of single crystal plasticity. The constitutive equations used have different formulations based on the micromechanisms of deformation and experimental measurements. The emphasis is on the effect of incorporating the micromechanisms of material behaviour on predicted macroscopic results. Several important phenomena and mechanisms, which are required for explaining creep properties as a function of stress, temperature and orientation are identified and included in the model. These include: activation of {111} and {111} slip systems, rigid body rotation, continuum damage, slip system softening, dislocation interaction, threshold behaviour and rafting. Model simulations are compared with experimental data in various deformation regimes. In a later part of the paper, the model is used to analyse the performance of a single crystal turbine blade. This enables the effect of the micromechanisms of deformation on overall component behaviour to be quantified.

Constitutive modelling of anisotropic creep deformation in single crystal blade alloys SRR99 and CMSX-4

A damage mechanics based model has been developed to model stress rupture and creep behaviour of the first and second generation single crystal superalloys SRR99 and CMSX-4. In this article the creep behaviour of CMSX-4 in several different orientations at 950°C is simulated using finite elements, these simulations are compared with the results of creep tests. In order that the effects of rotation and specimen bending can be accounted for in the analysis the entire creep specimen is modelled. The FE program ABAQUS has been used and the slip system model is written using a User MATerial subroutine (UMAT). EBSD (electron back scattered diffraction) measurements of the lattice rotations occurring during creep indicate that the active slip systems at 950°C are the <101>{111} and <112>{111} systems, our simulations show that the creep results can be explained by activating these two families of slip system. There is strong microstructural evidence that the significant components of the hardening matrix should be those causing self and latent hardening of the <101>{111} systems and latent hardening by the <101>{111} systems on the <112>{111} systems.

High-temperature corrosion resistance of Al-Re and Re coatings

The oxidation behavior in air at 1473 K, and sulfidation behavior in a H2S–H2 gas mixture with a sulfur partial pressure of 10−2 Pa at 973 K of Al–Re coated CMSX-4 were studied. Investigation on the sulfidation behavior of the Re-coated CMSX-4 was carried out in a H2S–H2 gas mixture with a sulfur partial pressure of 10−2 Pa at 973 K. The experimental results show that a Re-rich alloy layer was formed between an α-Al2O3 layer and the inner concentration zone of Ta and Ti for the CMSX-4 single crystal alloy with an Al–Re coating after oxidation. The Re-rich alloy layer containing Cr, W, Ni, Co, and Mo effectively inhibited the outward diffusion of alloying elements and the inward diffusion of Al. The Al/Re-coated CMSX-4 single crystal alloy had excellent sulfidation resistance; the Re-rich alloy layer, containing W, Ti, Ta, and Mo, which formed during the sulfidation process and located between the alumina scale and the CMSX-4 base alloy, plays a role in inhibiting the outward diffusion of alloying elements. The sulfidation resistance of CMSX-4 single-crystal alloy is greatly improved by a Re coating on the CMSX-4 alloy surface; this is attributed to a Re–Cr–W alloy layer that retarded the outward diffusion of cations and the oxide layer containing Ta, Ti, and Al, which inhibited the inward penetration of sulfur.

Influence of electron beam physical vapor deposited thermal barrier coating microstructure on thermal barrier coating system performance under cyclic oxidation conditions

Abstract The lifetimes of electron beam physical vapor deposited (EB-PVD) thermal barrier coating (TBC) systems with three different microstructures of the Y2O3-stabilized ZrO2 (YSZ) ceramic top layer were investigated in 1 h thermal cycles at 1100 and 1150°C in flowing oxygen. Single crystal alloys CMSX-4 and Rene N5 that had been coated with an EB-PVD NiCoCrAlY bond coat were chosen as substrate materials. At 1150°C all samples failed after 80–100 1 h cycles, predominantly at the bond coat–alumina interface after cooling down from test temperature. The alumina scale remained adherent to the YSZ after spallation. Despite the different YSZ microstructures, no clear tendency regarding differences in spallation behavior were observed at 1150°C. At 1100°C the minimum lifetime was 750 1 h cycles for CMSX-4, whereas the first Rene N5 specimen failed after 1750 1 h cycles. The longest TBC lifetime on CMSX-4 substrates was 1250 1 h cycles, whereas the respective Rene N5 specimens have not yet failed after 2300 1 h cycles. The failure mode at 1100°C was identical to that at 1150°C, i.e. the TBC spalled off the surface exposing bare metal after cooling. Even though not all specimens have failed to date, the available results at 1100°C suggested that both the substrate alloy chemistry and the YSZ microstructure significantly affect the spallation resistance of the TBC.

A Metallographic Technique for High Temperature Creep Damage Assessment in Single Crystal Alloys

The use of single crystal (SX) nickel-base superalloys will increase in the future with the introduction of SX blades into large gas turbines for base-load electricity production. Prolonged periods of use at high temperatures may cause creep deformation and the assessment of damage can give large financial savings. A number of techniques can be applied for life assessment, e.g., calculations based on operational data, nondestructive testing or material interrogation, but because of the uncertainties involved the techniques are often used in combination. This paper describes a material interrogation (metallographic) technique for creep strain assessment in SX alloys. Creep tests have been performed at 950°C on the SX alloy CMSX-4 and quantitative microstructural studies performed on specimens interrupted at various levels of strain. It was found that the strengthening γ′-particles, initially cuboidal in shape, coalesced to form large plates or rafts normal to the applied stress. The γ-matrix phase also formed plates. CMSX-4 contains ∼70 vol % γ-particles and after creep deformation the microstructure turned itself inside out, i.e., the gamma “matrix” became the isolated phase surrounded by the γ′-“particles.” This can cause problems for computerized image analysis, which in this case, were overcome with the choice of a suitable measurement parameter. The rafts reached their maximum length before 2 percent strain, but continued to thicken with increasing strain. Although of different dimensions, the aspect ratios (length/thickness ratio) of the gamma-prime rafts and the gamma plates were similar at similar levels of strain, increasing from ∼1 at zero strain to a maximum of ∼ 3 at about 1–2 percent strain. Analysis of microstructural measurements from rafting studies on SX alloys presented in the literature showed that the aspect ratios of the γ and γ′-phases were similar and that at a temperature of 950–1000°C a maximum length/thickness ratio of about 2.5–3.5 is reached at 1 to 2 percent creep strain. Measurement of gamma-prime raft or (or gamma plate) dimensions on longitudinal sections of blades is thus a suitable method for high temperature creep damage assessment of SX alloys. This gives a considerable advantage over conventional Ni-base superalloys whose microstructures are usually very stable with respect to increasing creep strain.

CMSX-11B

Abstract CMSX-11B is a non-rhenium containing single-crystal (SX) superalloy defined primarily for industrial turbine applications. The material develops a unique and extremely good blend of hot corrosion and oxidation resistance. It exhibits extremely good castability, employs relatively simple solution heat treatments, and provides creep strength that is as good or better than other first generation SX materials such as CMSX-2 (Alloy Digest Ni-417, November 1992), CMSX-3 (Alloy Digest Ni-420, January 1993), CMSX-4 (Alloy Digest Ni-447, March 1994), CMSX-6 (Alloy Digest Ni-418, December 1992), PWA 1480, and Rene N4. This datasheet provides information on composition and physical properties as well as creep. It also includes information on corrosion resistance as well as casting and heat treating. Filing Code: Ni-537. Producer or source: Cannon-Muskegon Corporation.

High temperature creep in a 〈001〉 single crystal nickel-base superalloy

Creep data at 982 C and 950 C have been presented for the single crystal alloy CMSX-4. At these temperatures the creep rate is initially very low and 50% of the creep life is consumed in reaching {approximately}1% strain. Some steady-state creep occurred at 950 C. Low strains are important; plots of log, strain rate versus log, strain give more weight to low strains and also showed that tertiary creep is strain controlled. A linear strain softening approach described the increase in creep rate reasonably well. Creep curves, where time had been normalized with respect to the rupture life, could be superimposed at a given temperature, in spite of widely differing rupture lives. Normalized creep curves can only be superimposed if primary creep is negligible, but could be used as a means of estimating the rupture life of a long term test after a few millistrains have been reached.

Aero Engine Test Experience With CMSX-4® Alloy Single-Crystal Turbine Blades

A team approach involving a turbine engine company (Rolls-Royce), its single-crystal casting facilities, and a superalloy developer and ingot manufacturer (Cannon-Muskegon), utilizing the concepts of simultaneous engineering, has been used to develop CMSX-4 alloy successfully for turbine blade applications. CMSX-4 alloy is a second-generation nickel-base single-crystal superalloy containing 3 percent (wt) rhenium (Re) and 70 percent volume fraction of the coherent γ′ precipitate strengthening phase. Its finely balanced composition offers an attractive range of properties for turbine airfoil applications. In particular the alloy’s combination of high strength in relation to creep-rupture, mechanical and thermal fatigue, good phase stability following extensive high temperature, stressed exposure and oxidation, hot corrosion and coating performance, are attractive for turbine engine applications where engine performance and turbine airfoil durability are of prime importance. The paper details the single-crystal casting process and heat treatment manufacturing development for turbine blades in CMSX-4 alloy. Competitive single-crystal casting yields are being achieved in production and extensive vacuum heat treatment experience confirms CMSX-4 alloy to have a practical production solution heat treat/homogenization “window.” The creep-rupture data-base on CMSX-4 alloy now includes 325 data points from 17 heats including 3630 kg (8000 lb) production size heats. An appreciable portion of this data was machined-from-blade (MFB) properties, which indicate turbine blade component capabilities based on single-crystal casting process, component configuration, and heat treatment. The use of hot isostatic pressing (HIP) has been shown to eliminate single-crystal casting micropores, which along with the essential absence of γ/γ′ eutectic phase, carbides, stable oxide, nitride and sulfide inclusions, results in remarkably high mechanical fatigue properties, with smooth and particularly notched specimens. The Re addition has been shown not only to benefit creep and mechanical fatigue strength (with and without HIP), but also bare oxidation, hot corrosion (sulfidation), and coating performance. The high level of balanced properties determined by extensive laboratory evaluation has been confirmed during engine testing of the Rolls-Royce Pegasus turbofan.

Change of phase morpholigies during creep of CMSX-4 at 1253K

Morphology changes of {gamma}{prime} precipitates during uniaxial stress of nickel base superalloy single crystals containing high volume fractions of {gamma}{prime} phase are well known. For negative misfit material and tensile stress in [001] direction, the initially cuboidal {gamma}{prime} particles transform into rafts oriented perpendicular to the load axis. In [011] orientation {gamma}{prime} rods, aligned perpendicular to the tensile external load direction, are generated. For the [111] load axis no shape changes were observed neither for tensile nor for compressive stresses. During investigations of creep anisotropy of CMSX-4 and microstructural evolution connected with creep in different orientations, the changes in matrix plate thickness occurring during creep at elevated temperatures are of interest. In [001] as well as in [110] orientation, bowing of dislocation dipoles in matrix channels is a frequently observed process which is controlled by the local resolved shear stress and the thickness of matrix plates. The rhenium containing alloy CMSX-4 has a volume fraction of about 70% of ordered {gamma}{prime} phase after standard heat treatment (solutioning: 1h/1,553 K, 2h/1,563 K, 6h/1,573 K and annealing 6h/1,413 K, 16h/1,143 K).

III - Stabilité mécanique des couches d’oxydes formées lors de l’oxydation de superalliages monocristallins

Mechanical stability of oxide layers resulting from several commercial single-crystal superalloys (AM3, CMSX4 and MC2 modified by Si and Hf addition) oxidation in oxygen at 1100°C was investigated.These layers are usually under compressive stresses as a result of differences in thermal expansion coefficients between oxide and metal. Thus, oxide spallation occurs regardless of cooling rate. The critical temperature drop to initiate spallation (ΔT) depends on the oxide layer thickness (ξ) and the interfacial rupture energy (γF ). In fact, for a given oxide/metal couple, [math] is constant (EVANS and LOBB model). AM3 and CMSX4 alloys follow this model while MC2 modified alloy has a diffe rent behavior. Addition of Si and Hf improves scale adherence according to a mechanism not yet investigated.

The location of atoms in Re- and V-containing multicomponent nickel-base single-crystal superalloys

The atomic structure of some Ni-base single-crystal superalloys has been investigated using atom-probe field ion microscopy (APFIM) and the results compared with numerical estimations obtained from the alloy design program (ADP) and the cluster variation method (CVM). Re-containing CMSX4 and V-containing RR2000 alloys, together with TMS63 are the subjects of this study. It is found that Ti, Ta and Hf have a strong preference for the γ′ phase, whereas Cr, Co, W, Re and Mo tend to dissolve in the γ phase. V has a very weak preference for the γ phase. The results agree very well with both ADP and CVM. The APFIM analyses have also revealed that Re atoms in CMSX4 tend to preferentially occupy the sites normally designated for Al atoms in the γ′ phase. It is demonstrated that the site occupancy of other alloying elements such as Ta, W, Mo and Co can be estimated accurately using CVM, although there are some discrepancies for the distributions of Cr, Ti and Ni. The effect of solute atom distribution on creep properties is discussed briefly.

Development of two rhenium- containing superalloys for single- crystal blade and directionally solidified vane applications in advanced turbine engines

A team approach involving several turbine engine companies using the concepts of simultaneous engi-neering has been used to successfully develop CMSX-4 ® alloy for turbine blade applications. CMSX-4 al-loy is a second-generation, single-crystal cast nickel-base superalloy containing 3% Re and approximately 70% volume fraction of γ. The high level of balanced properties determined by labora-tory evaluation has been confirmed during field testing of the Solarγ Mars T-14000 industrial gas turbine with CMSX-4 single-crystal (SX) blades in both the coated and bare condition. A similar collaborative ap-proach has resulted in the successful development of CM 186 LCγ alloy for complex, directionally solidi-fied (DS) columnar grain vane segments. CM 186 LC alloy is a second-generation DS columnar grain cast nickel-base superalloy containing 3% Re and approximately 65% volume fraction of γ. Excellent com-ponent producibility and quality is demonstrated. Turbine engine testing is scheduled to commence by the end of 1993.