Heat-resistant Superalloys Research Articles

Developments of metallic materials and a high-temperature structural design code for the HTTR

Abstract In the High-Temperature Engineering Test Reactor (HTTR), the hottest service temperature of class 1 metallic components exceeds 900°C under exposure to the primary helium coolant even at the normal operations, and control rods are also heated up to about 900°C at reactor scrams. For these components, Hastelloy X and Alloy 800H were selected from screening commercial heat-resistant superalloys. Hastelloy X is improved to have a superior compatibility with the primary coolant, and the improved version is called Hastelloy XR. The materials mentioned above and their service conditions are out of scope of the Japanese elevated-temperature structural design code, and further at the very high temperatures elastic-calculation-based design rules cannot satisfy the allowable limits due to very fast stress relaxations. Many research works on material characterizations and structural mechanics behavior, therefore, have been made in order to establish a high-temperature structural design code for both materials and also a creep analysis method for Hastelloy XR. Furthermore, a proposal was made against a key issue on tensile property. i.e., dynamic recrystallization for Hastelloy XR. This paper describes the results of research and development both on developing the metallic materials and on establishing the design code for these very high-temperature components.

Parallel EELS as a complementary tool in an Analytical TEM study of metal alloys

The advent of efficient parallel-detection electron energy loss spectrometers (EELS) in analytical transmission electron microscopes (ATEM) promotes rapid elemental characterization of various materials containing light, as well as heavy, elements at high spatial resolution. In the current study, the microstructures of Udimet 520 and HK-25 were investigated to integrate advances in parallel EELS methods with other ATEM techniques.Thin foils of Udimet 520, a nickel based heat-resistant superalloy, were obtained using common ion milling techniques. Precipitates of the HK-25, a heat resistant steel alloy, were obtained by etching (with Marble's reagent) a polished surface, extracting with a replicating Parlodian film, dissolving the film with amyl acetate and dispersing the resulting particles on holey carbon grids. A JEOL 2000FX ATEM fitted with a Gatan Model 666 EELS system was operated at 200 kV for studies of these alloys.

Simultaneous determination of metallic elements in precipitates and inclusions extracted from steel by inductively coupled plasma-atomic emission spectrometry

A study was made about the possibility of extracting complex precipitates, containing carbides, nitrides, intermetallic compounds, from low-alloy steels, high-alloy steels and heat-resistant super alloys by single electrolysis operation, followed by the simultaneous determination of all metallic elements in the precipitates by inductively coupled plasma-atomic emission spectrometry (ICP-AES). As a result, it was found that 4–5 metallic elements, such as Nb, Mo and Cr, whose determination had been considered difficult even by wet chemical analysis, can be simultaneously determined in the dissolved state in which Na 2S 2O 7 and tartaric acid (20%) added for the treatment of precipitates are concomitants. ICP-AES simplifies the analytical operation considerably and shortens the analytical time from about 18 h by conventional methods to about 1 h.

The role of the alloy matrix in the creep behavior of particle-strengthened alloys

The more obvious strengthening microstructural features in heat-resistant super-alloys are oxide dispersoids and/or γ′ precipitates. An interesting problem is the role that the strength of the alloy matrix plays in the creep resistance of these alloys. We sought an answer to this problem through the evaluation of experimental data on a host of oxide-dispersion- and/or precipitation-strengthened nickel-based alloys with various levels of matrix solid solution strengthening and through a generalized expression for creep rates which separates the matrix contributions from the particle contributions to the resisting stress and creep strength of these alloys. It is concluded that the major role of the alloy matrix in the creep behavior of these alloys is in determining the apparent stress dependence of the creep rates. Specifically, the stronger the matrix through solid solution strengthening, the less applied stress sensitive is the creep rate of the alloy. The implications of these findings with respect to alloy design for better creep resistance in multiphase alloys are also discussed.

耐熱合金の溶融塩付着による加速酸化のメカニズム

耐熱合金の溶融塩付着による加速酸化のメカニズム

耐熱合金Ｉｎｃｏ．７１３ＣのＴＬＰ Ｂｏｎｄｉｎｇに関する研究 組織およびクリープ強さについて

Structure and mechanical properties of heat resistant superalloy Inoc. 713C joint bonded by TLP (transient liquid phase) method being a new diffusion bonding process have been investigated fundamen-tally. Bonding was carried out by using insert metal (Ni-15Cr-3.5B) in a vacuum induction furnace, following by subsequent post heat treatment in order to promote homogenization in compositions. The following results were obtained.1. With increasing the bonding temperature and time, the structure at the bonded interface was improved and became similar to that of the base metal. On the other hand, when bonding was achieved in relatively low pressure, grain coarsening occurred near the bonded interface, on the contrary, the bonded interface made in the high pressure seemed to remain' as grain boundary.2. In bonding for about an hour, the constitution of the bonded interface considerably resembled that of the base metal.3. Solidification time of insert metal estimated from diffusion state of boron was approximately agreed with the result of structure observation.4. By selecting the suitable bonding conditions, tensile strength was easily equivalent to the base metal and also fairly good results about the creep strength were obtained though scattering somewhat.

Nucler Steelmaking in Japan

In July of 1973, a large scale national project* for nuclear steel making has started.This project will take six years and some 7, 300 million yen. Main organization of research is the Engineering Research Association for Nuclear Steelmaking.This association studies a total system and five sub-systems, which are heat exchanger, super heat resisting alloys, isoheat materials, reducing gas making and reduced pellts making. The development of Inuclear steel making technology as a national project aims at the completion of a direct-reduction steelmaking pilot plant which will be connected to the multi-purpose high-tempereture gas cooled reactor with a thermal output of 50 MW. With an aim at the above mentioned objective, efforts will be made to develop the design, construction and operational techneques for the pilot plant with a budget of about 7, 300 million yen to cover the relevant expenses for six years, commencing from 1973. To achieve this objective, the firstphase plogram will be directed toward research and development of technologies covering the system design and major components of the plant.The project, in the meantime, is being carried out so that the 50MWt multi-purpose high-temperature gas cooled reactors being planned by the Japan Atomic Energy Research Institute will attain their full power in 1982. The second phase of this national project accordingly will include the construction and operation plant for nuclear steelmaking to be directly connected to the multi-purpose high temperature gas cooled reactor. After success is achieved in the operation of the pilot plant, the scale of the plant will be expanded so that it will finally be developed into a commercial-scale plant. The period required to attain this prototype scale will be covered by the second-stage program.The nuclear steelmaking pattern we are expecting to realize is asshown in Fig. 1. Based on the given condition that the temperature of reducing gas to be blown into the reduction furnace should be 800 to 850°C, efforts will be made so that a reactor-outlet herium temperature of 1, 000°C can be guaranteed in consideration of temperature drop in the heat exchanger. The heat of 1, 000°C taken out of the multi-purpose high-temperature reactor will be used through the intermediate heat exchanger for manufacturing and heating of reducing gas. In Japan, the reducing gas will be manufactured from vacuum residual oils because of the scarcity of petroleum and natural gases. As for the steelmaking system has been adopted in which the reduced iron produced by shaft furnaces is turned into crude steel by electric furnaces. With this pattern of nuclear steelmaking, the first-phase progrm, extending over a period of six years, will aim at the completion of research and development of major relevant components such as a high-temperature heat exchanger, heat-resistant superalloys, high-temperature heat insulation materials, reducing-gas manufacturiug units and reduced iron manufacturing unts as well as researches for the development of system design to link the reactor system with the steel making system with a high degree of consistency and safety.* This Project based upon National Research and development Program by the Agency of Industrial Sciency and Technology, M. I. T. I.

UNILOY 19-9DX

Abstract UNILOY 19-9DX is a chromium-nickel heat resistant super alloy, capable of withstanding high static and dynamic stresses through at least 1200 deg. F. It has very low strategic index. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness, creep, and fatigue. It also includes information on low and high temperature performance, and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SS-41. Producer or source: Cyclops Corporation.

UNILOY 19-9DL

Abstract UNILOY 19-9DL is a chromium-nickel heat resistant super alloy, capable of withstanding high static and dynamic stresses through at least 1200 deg. F. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness, creep, and fatigue. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SS-19. Producer or source: Cyclops Corporation.