IN713C Superalloy Research Articles

Effects of yttrium on microstructure and low cycle fatigue properties of superalloy IN713C at high temperature

In order to improve the high temperature and low cycle fatigue performance of the IN713C alloy, trace amounts of yttrium (Y) element were added to such an alloy. The effect of Y on the microstructure and fatigue performance under push-pull loading condition of the IN713C alloy at 650 °C was investigated, and the fracture mechanisms of the IN713C alloy with different Y additions at strain amplitudes of 0.3%, 0.4% and 0.5% were also investigated. The results showed that addition of Y significantly increased the fatigue life of the IN713C alloy under different strain amplitude values. Compared with the traditional IN713C, the fatigue life of the alloy with 300 ppm Y was increased by 44.4%, 213.3%, and 61.4%, and that of the alloy with 500 ppm Y was increased by 184.6%, 66.1%, and 172.1%, respectively, at the strain amplitudes of 0.3%, 0.4%, and 0.5%. Shrinkage pores were found to be the main crack source at low strain amplitude (0.3%), while carbides and other interdendritic precipitates were the source of cracks at high strain amplitude (0.4% and 0.5%). The addition of Y increased the fatigue life of the IN713C alloy by reducing shrinkage and refining carbides and grain size.

Microalloying effects of Y on performance of cast nickel-based superalloy IN713C

Microalloying is a cost-effective strategy to develop high performance nickel-based superalloys. Here, the mechanisms of rare earth Y in IN713C on purification, mechanical property improvement, and microstructure modification were systematically investigated. Via melt purification of Y, the O, N, and S elements are reduced to 5 ppm in the IN713C alloy. By adding Y to 74 ppm, the yield strength, tensile strength, and elongation of the IN713C alloy at 650 °C are increased by 12.2%, 14.5%, and 66%, respectively. Microstructure analysis indicated that the strength of the alloy is improved by refining the size and increasing the volume fraction of the γ’ phase. The plasticity of the alloy is improved by modifying the morphology and distribution of MC carbides. The modification of carbide morphology can be attributed to the enrichment of Y at the surface of carbides and the change of segregation of Nb, which is the main carbide-formation element.

Solidification characteristics and high temperature tensile properties of Ni-based superalloy IN713C

The solidification characteristics and high temperature tensile properties of IN713C superalloy were investigated using directional solidification methods at withdrawal rates of 10, 50 and 100 µm/s, respectively. The results show that carbide morphologies change from block and long strip to short rod and granular with increasing withdrawal rate. The increase of withdrawal rate promotes the microsegregation of Mo, Nb and Zr, and contributes to precipitation of the γ/γ’ eutectic and boride. With the withdrawal rate increasing from 10 µm/s to 50 µm/s, the high temperature yield strength, ultimate strength and elongation of the IN713C alloy increased by 11.8%, 18.3% and 64% respectively. The increase of the γ/γ’ eutectic and boride lead to slight decrease in strength when the withdrawal rate increased from 50 µm/s to 100 µm/s. The fractographic observation of tensile specimen indicates that the integrate carbide particles are an overwhelming majority at a higher withdrawal rate. When the withdrawal rate decreases, the particles become larger and more secondary cracks are generated. The morphology of carbides affects the tensile fracture mechanism of the alloy. With the decrease of carbide size, the crack source of the IN713C alloy changed from brittle carbides to the interface between carbide and matrix.

Microstructure and phases structure in nickel-based superalloy IN713C after solidification

The effects of cooling rate on microstructure and microtexture development during solidification of IN713C nickel-based superalloy have been studied with a range of cooling rate from 0.3 °C/s to 4 °C/s (air cooled). The results showed an increase in grain size (from 140 μm to 2 mm) and carbides volume fraction (1.3% to 2%) with increasing cooling rate. It was also found that primary γ′ size decreased with increasing cooling rate. Furthermore, it was demonstrated that the dendrite structure was weakened with decreasing cooling rate. The dendrite structure was nearly eliminated at slowest cooling rate applied here (0.3 °C/s). Eutectic clusters that mainly consisted of large γ′, Ni7Zr2, M3B2 type boride and/or MC-type carbide precipitates were identified in air cooled samples. These undesirable clusters presented specific morphologies and their density (volume fraction) was found to decrease with decreasing cooling rate. Moreover, predominant phase separation of γ′ is observed in the slowest cooling sample and in interdendritic areas in the fastest cooling sample. Hardness test results showed a slight decrease in hardness with decreasing cooling rate. This may result from the combined effects of detrimental effect of larger γ′ and beneficial effect of smaller grain size in slowest cooling sample. The observations demonstrated here can contribute greatly to the modification of standard investment casting parameters that applied during IN713C turbine wheels production for turbochargers.

Powder injection moulding of Inconel 713C alloy

ABSTRACTTo find a proper super alloy applied to gasoline engine turbochargers which demand a high operating temperature over 950°C, the IN713C super alloy was investigated in this study. The rheological properties of feedstock, density, microstructure and mechanical properties were measured. The proper powder loading was 61 vol.-%. Through the analysis of viscosity, 160°C was supposed to be more suitable for the injection. After debinding, most binder components were removed. A reasonable debinding process was formulated. Two pre-sintering temperature (850, 950°C) were investigated, then 850°C was considered to be more proper relatively. The samples were sintered at different temperatures for various time. The best properties of sintered parts were obtained when sintered at 1300°C for 3 h, the density of sintered parts was 7.83 g cm−3 while the hardness was 43.6 HRC and tensile strength was 1216.9 MPa.

The Influence of Shell Mold Composition on the As-cast Macro- and Micro-structure of Thin-Walled IN713C Superalloy Castings

In the investment casting process, the building of ceramic layers around the wax pattern is the main time-consuming stage. Increasing their number ensures sufficient mechanical properties, but also lengthens the whole process, including drying time and preheating of the mold. Four molds for casting Ni-based superalloy IN713C were strengthened by glass fibers, included in the slurry, and metal powder, of Al, Cu, Fe or Ni, in the coverage. Castings were subjected to microstructural investigations in order to find out if the new design can be promising for the manufacture of jet engine components. Bend tests revealed that the green strengths of all new molds were higher, at least 3.65 MPa, than that of the unmodified molds, 3.0 MPa. Optical microscopy revealed that the composition of a mold had a strong influence on stereological parameters of equiaxed IN713C grains. Microstructural observation and hardness measurements of castings revealed differences in the volume fraction of strengthening phases, porosity and hardness. The microstructure due to the complex chemical composition of IN713C consisted of several phases including ternary eutectics as a consequence of L → γ + Ni7Zr2 + (Nb, Zr)C.

Effect of Surface Treatment on High-Temperature Oxidation Behavior of IN 713C

The effects of surface preparations on oxidation kinetics and oxide scale morphology for the commercially available Ni-based superalloy IN 713C have been investigated. The ground and polished samples were exposed in air at 800-1100 °C. The ground specimens were found to demonstrate lower oxidation kinetics compared to those after polishing. The grinding also affected the oxide scale morphology, resulting in a protective alumina scale, while the polished samples developed Ni-/Cr-rich mixed oxides on the surface. Better oxidation resistance of the ground surfaces is related to a higher concentration of defects in the near-surface region introduced by cold working. These defects facilitate the outward transport of the scale-forming element Al and thus are beneficial for protective oxidation. The oxidation mechanism at lower temperatures was introduced. The model based on the generalized Darken method and multiphase approximation was proposed.

The effects of microstructure and microtexture generated during solidification on deformation micromechanism in IN713C nickel-based superalloy

Nickel-based superalloy IN713C produced through investment casting route is widely used for turbocharger turbine wheels in the automotive industry. The produced microstructure and microtexture are not homogeneous across the turbine component due to geometrical factors and localised cooling rate during the casting process, which give rise to inhomogeneous deformation during service. In the present paper, two kinds of in-house fatigue tests, Low Cycle Fatigue (LCF) and High Cycle Fatigue (HCF), were conducted at 600 °C in attempt to simulate the actual fatigue conditions experienced by turbine wheels in turbocharger. From Geometrically Necessary Dislocation (GND) distributions and strain analyses, it is concluded that microstructure heterogeneity such as carbide precipitates distribution within dendritic structure network determine the failure micromechanics during LCF tests. In the early stage of LCF loading, crack principally initiated within near surface carbides that have been oxidised during high temperature exposure. The higher GND density at the tip of carbide precipitates due to oxidation volume expansion are found to facilitate easy cracks initiation and propagation. Moreover, the cluster-like carbides network and its distribution can accelerate oxidation process and crack growth effectively. Furthermore, in the later stage of crack propagation during LCF, the weak interdendrite areas rotate to accommodate increased strain leading to faster cracks propagation and hence final catastrophic failure. Serial section technique for 3-D visualisation was employed to investigate the crystallographic grain orientation correlation with fracture mechanics during HCF loading. It appears that the microtexure and grain orientations are more critical than the alloy microstructure in an area with a relatively uniform carbides distribution and weak dendrite structure where HCF failure occurred. Based on the slip trace analysis, it was found that most faceting occurred in Goss grains (<110>//LD) and on slip system with the highest Schmid factor. It is concluded that cracks were initiated on planes with high Schmid factors and assisted by the presence of porosity.

Surface preparation effect on oxidation kinetics of Ni-base superalloy

In the present study an oxidation behavior of commercially available Ni-base superalloy IN 713C with different surface finishing, namely polished up to 1 μm diamond paste (resulting in Ra = 0.023) and ground by SiC paper with 80 grit (Ra = 1.23), were investigated at 950°C in air. It was found that ground sample developed very thin, protective α-Al2O3 scale. Moreover, locally formation of θ-Al2O3 in the forms of spikes was observed. For the sample with polished surface formation of outer chromia scale accompanied with internal oxidation of aluminum was observed. Moreover, for specimen which does not form continuous alumina scale or sub-scale, the GD-OES depth profiles showed an enrichment of boron at the oxide scale/alloy interface. It was proposed that the formation of protective alumina scale on ground samples is caused by introducing the defects into the near-surface region of the material, which are an easy diffusion paths for the elements forming a protective oxide scales.

Metallographic Study and Repeatability Analysis of γ' Phase Precipitates in Cored, Thin-Walled Castings Made from IN713C Superalloy

AbstractThe study describes the influence of a surface modification in cored, thin-walled castings of blades from IN-713C nickel superalloy onγ'phase precipitates. The blades were produced by using the investment casting process in the laboratory conditions as parts for a low-pressure turbine rotor. The microstructural observations of theγ'phase precipitates on the cross sections of the blades were performed. The observations were followed by quantitative metallography evaluation, and finally, a comparison of the precipitates between one blade with the conventionally applied ceramic core and one with the core covered layer contained a surface modifier (5% of CoAl2O4) was made.

The Impact of the Thickness of the Ceramic Shell Mould on the (γ + γ′) Eutectic in the IN713C Superalloy Airfoil Blade Casting

AbstractIn the study the wall thickness of ceramic shell mould influence on (γ+γ′) eutectic in the IN713C nickel-based superalloy airfoil blade casting was described.Two castings formed as a blade from two wax pattern assemblies were analysed. In the experiment in one pattern the thick ceramic layer was obtained on pressure side and in another one on suction side of the airfoil blade. The microstructure of the cross-sections of the castings were observed on polished and etched metallographic specimens. The microstructure and phases chemical compositions of specimens was analyzed by using the scanning electron microscope Hitachi S-4200 equipped with EDS. It was established, that wall thickness of ceramic shell mould affect size, shape and volume fraction of (γ+γ′) eutectic islands in airfoil blade made from IN713C superalloy.The analysis was provided in accordance to the typical statistical methodology [1].

Influence of cobalt addition on microstructure and hot workability of IN713C superalloy

In the present research, the influence of Co addition on the microstructure and hot workability of IN713C alloy was investigated in detail by scanning electron microscope (SEM), transition electron microscope (TEM) and electron backscattering diffraction (EBSD) etc. Substitution of Ni by Co leads to lower driving force for formation of γ′ phase. In addition, with the increase of Co fraction, the γ′ phase precipitates turned finer and more cuboidal shape. As a result, the hot workability of IN713C alloy was improved significantly by Co addition. This can be ascribed to the decrease in activation energy, misfit between γ/γ′ phase lattice, the stacking fault energy as well as the fraction of γ′ phase at elevated temperature after adding Co.

The fixed-effects analysis of the relation between SDAS and carbides for the airfoil blade traces

Abstract The primary objective was to test a usefulness of the specific fixed-effect model for the analysis of quantitative relationships gathered from the image analysis of the material microstructures. The dataset was obtained from the investigation of turbine blades made from superalloy IN713C. The analysis based on the general linear model resulted in informative plots revealing mutual relationships between secondary dendrite arm spacing and the mean plane section area of carbides in the material. Directions for further research also were obtained.

ATD and DSC Analysis of IN-713C and ZhS6U-VI Superalloys

Abstract Paper presents the results of ATD and DSC analysis of two superalloys used in casting of aircraft engine parts. The main aim of the research was to obtain the solidification parameters, especially Tsol and Tliq, knowledge of which is important for proper selection of casting and heat treatment parameters. Assessment of the metallurgical quality (presence of impurities) of the feed ingots is also a very important step in production of castings. It was found that some of the feed ingots delivered by the superalloy producers are contaminated by oxides located in shrinkage defects. The ATD analysis allows for quite precise interpretation of first stages of solidification at which solid phases with low values of latent heat of solidification are formed from the liquid. Using DSC analysis it is possible to measure precisely the heat values accompanying the phase changes during cooling and heating which, with knowledge of phase composition, permits to calculate the enthalpy of formation of specific phases like γ or γ′.

Quantitative Evaluation of Porosity in Turbine Blades Made of IN713C Superalloy After Hot Isostatic Pressing

Abstract The aim of this paper is an assessment of the influence of hot isostatic pressing treatment on porosity of cast samples - turbine blades and vane clusters made of the IN713C superalloy. Two variants of HIP treatments, differing in pressure from each other, have been used. The quantitative evaluation of the porosity was performed using light microscopy and quantitative metallography methods. The use of the hot isostatic pressing significantly decreased the volume fraction and size of pores in the test blades, the remaining pores after the HIP process being characterized by a round shape. The increased pressure has caused significant reductions in the area fraction and size of the pores.

Effect of hot isostatic pressing on the microstructure of turbine blade airfoil made of nickel-base superalloy

Abstract Turbine blades are flight safety parts in the jet engine. Therefore they should be characterized by very good mechanical properties, especially high creep resistance and fatigue strength at high temperature. The mechanical properties of blades made of nickel-based superalloys depend on the microstructure of the casting and its porosity [1,2]. The aim of this paper is evaluation of effect of hot isostatic pressing (HIP) on microstructure of blade airfoil made of IN713C superalloy in four important zones: (i) leading edge, (ii) trailing edge, (iii) suction side and (iv) pressure side. HIP treatment was carried out proving some significant microstructural changes. Electron backscatter diffraction (EBSD) analysis reveals some structural changes what may facilitate diffusion processes leading to simplify of a heat treatment (solution treatment and aging).

Influence of variable casting wall thickness and shell mold material and its thermal properties on secondary dendrite arm spacing in IN 713C superalloy castings

Influence of variable casting wall thickness and shell mold material and its thermal properties on secondary dendrite arm spacing in IN 713C superalloy castings

Characterizing the Effects of Hot Isostatic Pressing on IN713C Superalloy Blade Microstructure by Electron Backscatter Diffraction

The integrity of turbine blades is essential for the safe operation of jet engines. Thus, the mechanical properties, especially creep resistance and fatigue strength at high temperatures, must be thoroughly optimized. In particular, it has previously been observed that the mechanical properties of blades depend on the microstructure and porosity resulting from the casting process. To decrease the internal porosity generated by investment casting, hot isostatic pressing can be applied. This paper aims to evaluate the effects of hot isostatic pressing on the microstructure of IN713C alloy blades. Two variants of hot isostatic pressing treatment, differing in pressure, were carried out, and each resulted in lowered porosity. Microstructural investigations, performed using scanning electron microscopy and electron backscatter diffraction revealed significant changes of γ′ particles and high strain intensity in the surface layer of the blades after hot isostatic pressing treatment.

Influence of Modification and Casting Technology on Structure of IN-713C Superalloy Castings

Abstract The paper presents the results concerning impact of modification (volume and surface techniques), pouring temperature and mould temperature on stereological parameters of macrostructure in IN713C castings made using post-production scrap. The ability to adjust the grain size is one of the main issues in the manufacturing of different nickel superalloy castings used in aircraft engines. By increasing the grain size one can increase the mechanical properties, like diffusion creep resistance, in higher temperatures. The fine grained castings. on the other hand, have higher mechanical properties in lower temperatures and higher resistance to thermal fatigue. The test moulds used in this study, supplied by Pratt and Whitney Rzeszow, are ordinarily used to cast the samples for tensile stress testing. Volume modification was carried out using the patented filter containing cobalt aluminate. The macrostructure was described using the number of grains per mm2, mean grain surface area and shape index. Obtained results show strong relationship between the modification technique, pouring temperature and grain size. There was no significant impact of mould temperature on macrostructure.

Characterization of IN713C superalloy microstructure after high temperature creep test by LM, SEM and STEM

Characterization of IN713C superalloy microstructure after high temperature creep test by LM, SEM and STEM