Long term heating effects at 1173 K and 1273 K on microstructural rejuvenation in various modified alloys based on GTD-111

This research work studied and evaluated the effects of reheat treatment conditions, which consisted of solution treatment at a temperature of 1448 K for 14.4 ks, followed by air cooling and precipitate aging at a temperature of 1118 K for 86.4 ks, on the microstructural rejuvenation or refurbishment of various modified alloys based on the cast nickel base superalloy, GTD-111 with aluminum, nickel and/or cobalt additions after long term heating at temperatures of 1173 K and 1273 K for 1440 ks. From the results obtained, it was found that the reheat treatment conditions applied are more suitable for microstructures after long term heating at a temperature of 1173 K. However, such reheat treatment conditions could not fully return reheat treated microstructures to microstructures similar to those of previous research work. It seems that the selected solutioning temperatures and/or times were not sufficient to completely dissolve all coarse gamma prime particles after long term heating for all samples with alloying additions. Typical size and area fractions of the gamma prime particles of the reheat treated microstructures are very similar to those of the original alloyed ones but with lower values, especially those related to the size of the gamma prime particles.

Weldability and Properties of Newly Developed LW4280 High Gamma Prime Nickel Based Superalloy for 3D AM and Repair of Turbine Engine Components

Chemical composition, structure, mechanical and oxidation properties of welds produced utilizing laser direct energy deposition process of a newly developed LW4280 welding powder will be presented. Crack-free and high-density specimens were fabricated for manufacturing standard and subsized tensile test samples as per ASTM E-8. Optical and scanning electron microscopy revealed the formation of epitaxial grain growth during solidification of the welding pool followed by precipitation of fine gamma prime phase during the reheating from the subsequent weld layers. A sub-solvus primary aging temperature determined using Thermo-Calc software followed by secondary aging resulted in precipitation of above 49% of cuboidal γ′ phase. Excellent ultimate tensile strength of 1310 MPa (190 ksi), 0.2% yield strength of 855 MPa (124 ksi), and elongation of 18.7% were measured at ambient temperature. At 926°C (1700°F), the tensile testing yielded of 579 MPa (84 ksi), 0.2% yield strength of 462 MPa (67 ksi), and elongation of 18.8%. Cyclic oxidation resistance of the LW4280 weld material at 1120°C (2048°F) was superior to Rene 80 and Mar M247 while slightly below Rene 142.

EFFECT OF TREATMENT SOLUTION ON THE MICROSTRUCTURE AND MICROHARDNESS OF TERNARY Ni-Al-Nb ALLOY DOPED WITH TITANIUM

EFFECT OF TREATMENT SOLUTION ON THE MICROSTRUCTURE AND MICROHARDNES OF TERNARY Ni-Al-Nb ALLOY DOPED WITH TITANIUM. Nickel-based superalloys have been widely used in various applications, which require high strength at high temperatures. Most types of these superalloys is age-hardenable because they have γ’ particles' chemical composition Ni3(Al, Ti) in γ’-phase matrix. This research will be used alloy Ni-Al-Nb added alloying elements Ti. This research was conducted to study the mechanical properties, microstructure conditions in some alloys Ni-Al-Nb added distinction Titanium element (0,5% and 1% Ti) using the method of aging temperature variation performed at a temperature of 650 °C,700 °C and 750 °C with a holding time 4 hours and air cooling. Tests were conducted to determine the characterization of the specimen includes testing metallographic optical microscope, Rockwell hardness C and SEM- EDS,XRD. Results obtained from this research that addition of titanium element affecting the hardness values as well as the results of the cast, solution treatment and aging process results. The 1% Titanium content can affect the gamma prime coarsening and make the grain on the microstructure result smooth.

The Microstructure and Properties of Laser Shock Peened CMSX4 Superalloy

The influence of laser shock peening on the surface morphology and microstructure of single-crystal CMSX4 nickel-based superalloy was investigated by optical profilometry and atomic force microscopy, scanning and transmission electron microscopy as well as scanning-transmission electron microscopy in high-angle annular dark-field mode. Maps of chemical elements distribution in the laser-affected areas were determined using energy-dispersive X-ray spectroscopy. Furthermore, after the LSP, nanohardness tests were conducted on the cross section of the treated samples as well as the untreated material. Laser shock peening caused an ablation and melting of the surface layer and hence enlarged the surface roughness. Beneath the surface, in the laser shock-peened areas, severe distortion of the regular $$ {\gamma \mathord{\left/ {\vphantom {\gamma {\gamma^{\prime}}}} \right. \kern-0pt} {\gamma^{\prime}}} $$ γ / γ ′ microstructure was observed. In the surface layer, down to about 15 μm, shear bands of localized deformation were formed. Moreover, the result showed that the average nano-hardness value was obviously increased in the laser-treated region.

Review Microstructure of Nickel-Based Single-Crystal CMSX-4 Superalloy after Electrochemical Machining

A special position has been created for using the nickel-based single-crystal CMSX-4 superalloy at high temperatures due to the improved mechanical properties of this material and the absence of grain boundary in the crystal lattice. Also, electrochemical machining can be an effective method for machining this superalloy due to its unique performance in metal machining, like creating stress-free surfaces, high-level surface smoothness, and machining of complex geometries. This single crystal superalloy's microstructure consists of three phases: Gamma, Gamma prime, and a bit of carbide. Gamma prime is distributed cubically and homogeneously in the Gamma field without any boundaries and as a single crystal. It is essential not to change the microstructure after the production process or machining. In the present research, electrochemical machining was performed on CMSX-4 single crystal superalloy. The workpiece's microstructure was then investigated before and after electrochemical machining using scanning electron microscopy and EDS analysis from two sides. No changes were seen in CMSX-4 infrastructure after electrochemical machining EDS analysis and Images.

Effect of cooling rates of solution treatment on rejuvenation heat-treated microstructures of a cast nickel-based superalloy

IN-738 turbine blade samples, deteriorated after long term service at high temperatures, were solution heat-treated at two temperatures, 1398 K and 1473 K, for 7.2 ks. Subsequently, the samples were cooled down in different atmospheres, in air and in furnace, for the purpose of studying the effects of different cooling media (rates) on the restored microstructures. Following this, the samples were aged at 1118 K for 43.2 ks and 86.4 ks in order to determine the characteristic of re-precipitated gamma prime particles. A scanning electron microscope (SEM) and ImageJ analysis software were used. The results show that the cooling in air provided gamma prime particles re-precipitating in spherical shape while the cooling in a furnace resulted in coarse gamma prime particles re-precipitating in irregular shape. The samples solutionized at 1398 K for 7.2 ks cooled down in air and then aging at 1118 K provided bimodal microstructure, while the sample solutionized at 1473 K for 7.2 ks, followed by air cooling and aging at 1118 K generated unimodal γ’ precipitation in spherical shape. Cooling in a furnace provides coarse γ’ recipitated particles in more irregular shape for the both solutionizing temperatures studied here. Cooling in a furnace provides coarse γ’ precipitated particles in more irregular shape for the both solutionizing temperatures studied here.