GH4169 Overview

GH4169 is a nickel-based superalloy strengthened by precipitation of body-centered tetragonal γ'' and face-centered cubic γ' phases. It exhibits excellent comprehensive properties within the temperature range of -253 to 700°C, with the highest yield strength among wrought superalloys below 650°C. The alloy also demonstrates good fatigue resistance, radiation resistance, oxidation resistance, corrosion resistance, along with favorable workability, weldability, and long-term microstructural stability. It is capable of manufacturing various complex-shaped components and has been widely used in aerospace, nuclear energy, and petroleum industries within the aforementioned temperature range.

Another characteristic of this alloy is its high sensitivity to hot-working processes. By understanding the precipitation and dissolution behavior of phases in the alloy, as well as the relationship between microstructure, processing, and properties, reasonable and feasible process regulations can be formulated to meet different strength levels and application requirements. The available product forms include forgings, forged bars, rolled bars, cold-drawn bars, discs, rings, plates, strips, wires, and tubes. These can be used to manufacture disks, rings, blades, shafts, fasteners, elastic components, sheet structural parts, casings, and other components for long-term use in aviation.

GH4169 Chemical Composition

Physical Properties of GH4169:

Mechanical Properties of GH4169 at Room Temperature:

GH4169 Heat Treatment

GH4169 alloy can undergo different heat treatment processes to control grain size, δ-phase morphology, distribution, and quantity, thereby achieving various levels of mechanical properties. The heat treatment processes for the alloy are divided into three categories:

(1010-1065)°C ±10°C, 1h, oil cooling, air cooling, or water cooling + 720°C ±5°C, 8h, furnace cooling at 50°C/h to 620°C ±5°C, 8h, air cooling.

Material treated with this process exhibits coarse grains with no δ-phase at grain boundaries or within grains, resulting in notch sensitivity. However, it benefits impact properties and resistance to low-temperature hydrogen embrittlement.

(950-980)°C ±10°C, 1h, oil cooling, air cooling, or water cooling + 720°C ±5°C, 8h, furnace cooling at 50°C/h to 620°C ±5°C, 8h, air cooling.

Material treated with this process contains δ-phase at grain boundaries, which helps eliminate notch sensitivity. This is the most commonly used heat treatment process, also known as the standard heat treatment process.

720°C ±5°C, 8h, furnace cooling at 50°C/h to 620°C ±5°C, 8h, air cooling.

After this treatment, the material contains less δ-phase, improving strength and impact properties. This process is also known as the direct aging heat treatment process.

GH4169 Melting and Casting Processes

The alloy's melting processes are divided into three categories: vacuum induction melting plus electroslag remelting; vacuum induction melting plus vacuum arc remelting; vacuum induction melting plus electroslag remelting plus vacuum arc remelting. Depending on the application requirements of the components, the appropriate melting process can be selected to meet specific needs.

GH4169 Application Overview and Special Requirements

It is used to manufacture various static and rotating components in aerospace engines, such as disks, rings, casings, shafts, blades, fasteners, elastic components, gas conduits, sealing elements, and welded structures. It is also used in the nuclear energy industry for elastic components and grids, as well as in the petroleum and chemical industries for various parts.

In recent years, with continuous research and expanding applications of this alloy, numerous new processes have been developed to improve quality and reduce costs. These include helium cooling during vacuum arc remelting to effectively reduce niobium segregation; spray forming to produce rings, lowering production costs and shortening cycles; and superplastic forming to expand the range of producible components.

GH4169 Forming Properties

Due to the high niobium content in GH4169 alloy, the degree of niobium segregation is directly related to the metallurgical process. The melting speed during electroslag remelting and vacuum arc remelting, as well as the quality of the electrode, directly affect the material's properties. Fast melting speeds can lead to niobium-rich black spots; slow melting speeds can cause niobium-poor white spots. Poor surface quality or internal cracks in the electrode can also contribute to white spot formation. Therefore, improving electrode quality, controlling melting speed, and increasing the solidification rate of the ingot are key factors in the melting process. To avoid severe elemental segregation, the maximum ingot diameter used currently does not exceed 508mm.

The homogenization process must ensure complete dissolution of the L-phase in the ingot. The duration of the two-stage homogenization of the ingot and the secondary homogenization of the intermediate billet depends on their diameters. The control of the homogenization process is directly related to the degree of niobium segregation in the material.

The currently used homogenization process of 1160°C for 20h + 1180°C for 44h is insufficient to eliminate segregation in the center of the ingot. Therefore, the following homogenization process is recommended:

GH4169 Machining and Grinding Properties

The alloy can be satisfactorily machined. During machining, it is essential to ensure that arcs meet design requirements and transitions are smooth. Sharp corners, pits, and scratches are not allowed during machining, assembly, or transportation, as these defects can lead to excessive stress concentration, potentially causing serious accidents during use.

The above is an introduction to the nickel-based superalloy GH4169 (GH169).