Bradley Perrett, Asia-Pacific bureau chief of the Washington-based Aviation Week & Space Technology says that Chinese demand for rare metal - Rhenium reveals improved Chinese combat aircraft engines
China needs large supplies of rhenium — a rare metal that increases the temperature-resistance of turbine blades — to design and produce an engine that can handle higher internal temperatures, increasing performance and durability. Perrett claims that China is actually following the global pattern of rhenium consumption because around 80% of the figure is used to produce aviation turbines. The use of rhenium can imply two upward steps in turbine metallurgy, the expert said. It can be used to improve nickel-based superalloys, while those alloys can be formed as single-crystal blades.
Both technologies allow a turbine, especially a high-pressure one, to operate at a greater temperatures, according to Perrett."Rhenium melts at 3,182C (5,759F), compared with 1,455C for nickel," said Perrett, "The improved superalloys are almost certainly earmarked for combat aircraft engines, such as the WS-10 Taihang, which powers the J-10 and J-11 fighters. Chinese production of high-bypass turbofans must be very low, and their performance is not so important."
China needs large supplies of rhenium — a rare metal that increases the temperature-resistance of turbine blades — to design and produce an engine that can handle higher internal temperatures, increasing performance and durability. Perrett claims that China is actually following the global pattern of rhenium consumption because around 80% of the figure is used to produce aviation turbines. The use of rhenium can imply two upward steps in turbine metallurgy, the expert said. It can be used to improve nickel-based superalloys, while those alloys can be formed as single-crystal blades.
Both technologies allow a turbine, especially a high-pressure one, to operate at a greater temperatures, according to Perrett."Rhenium melts at 3,182C (5,759F), compared with 1,455C for nickel," said Perrett, "The improved superalloys are almost certainly earmarked for combat aircraft engines, such as the WS-10 Taihang, which powers the J-10 and J-11 fighters. Chinese production of high-bypass turbofans must be very low, and their performance is not so important."
DD6 is China's second-generation nickel-based single-crystal superalloy
1. First generation nickel-based single-crystal superalloy was called DD3. This technology was probably used in the WS-10A and WS-13 turbofan engines.2. Newer second-generation nickel-based single-crystal superalloy is named DD6. This latest technology will probably be incorporated into the WS-15 turbofan engine.
Figure 1. (a) HAADF image of alloy DD6 before the creep test. (b) Element mapping images of major constituents corresponding to the area denoted by a white rectangle in (a). (c) Distribution of elements Re and W along the direction perpendicular to the interfaces. The dashed vertical lines show schematically the γ/γ′ interface.
Source: ScienceDirect.com - Scripta Materialia - Distribution of rhenium in a single crystal nickel-based superalloy
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DD6 single crystal alloy TLP diffusion bonding process
"DD6 single crystal alloy TLP diffusion bonding process
发表于 2012/08/17 由 admin
DD6 is China's second-generation nickel-based single crystal superalloy with high temperature strength, good overall performance, and organizational stability. With the first generation of nickel-based single crystal superalloy DD3, Cheng Wen capacity increase of about 40 ° C; compared with foreign widely used second-generation single crystal alloys, tensile properties, long-lasting performance, oxidation resistance and heat corrosion all reached and even some more than its level, and containing rhenium low low-cost advantage. Of the alloy is suitable for the production of work below 1100 ℃, gas turbine blade and other high temperature parts with complex cavity [1-3]. Apparently alone casting technology to manufacture the hollow blades with complex cavity is very difficult, even impossible, only the casting and welding the two processes combining to make it a reality. The single crystal alloy as a single crystal highly efficient gas-cooled modular blade manufacturing process, the most important one of the key technologies, foreign countries have to conduct more studies, transient liquid phase diffusion bonding (TLP diffusion bonding) on ??the single crystal turbine blades connection shows a clear advantage and feasibility [4,5]. P & W Company has adopted the TLP diffusion bonding technology to produce outside the compound single crystal blades, and is used on the F100 engine [4]. Developed in our second-generation nickel-base single crystal superalloy DD6 for the study, TLP diffusion welding head the organization and performance analysis.
A test of materials, methods and equipment
Test the parent material for the DD6 single crystal alloy, its composition and typical rupture properties shown in Table 1, the standard heat treatment specifications for the 1290 ° C, 1h from +1300 ° C, 2h +1315 ° C, 4h, air-cooled +1120 ° C, 4h, air-cooled +870 ° C , 32h, air-cooled. TLP diffusion bonding intermediate layer alloy is prepared for DD6 are basically the same, the main component DD6 base metal, adding a certain amount of B as the melting point depressant elements, use the form -150 purpose powder.
Surface preparation before welding in order to prevent the machining stress lead to recrystallization in the base metal in the welding thermal cycle, using the + wire cutting + sanding base metal heat treatment processing. Before welding, all samples with acetone ultrasonic cleaning to oil.
Diffusion welding temperature used to match the temperature of solution treatment with the base metal, ie, 1290 ° C, holding time requirements through tests to determine in accordance with the joints lasting performance.
Docking sample connector metallographic sample and performance samples are first 0.1mm thick stainless steel gasket sandwiched between both ends of the specimen connected surface, and TIG welding positioning, then as usual brazing fill plus brazing powdery intermediate layer alloy is placed in the sample above the binder positioning. Connection, the intermediate layer alloy melt into the cracks in the formation of joints. In order to ensure that the two matching samples of crystal orientation consistent to avoid or reduce the formation of the joint to reduce the mechanical properties of grain boundaries in the test specimen strict matching processing and precise positioning of assembly and welding to ensure that two specimens relative position.
Figure 1 shows the form of the specimen measured the lasting high temperature mechanical properties, optical microscopy, scanning electron microscopy, energy dispersive analysis by means of diffusion welding the head of the organization of different holding time were observed and analyzed."
China built indigenous DD3 nickel-based single-crystal superalloys prior to 1995
Fig. 1. Microstructure of the DD3 single-crystal superalloy, respectively, solidified at undercooling of (a) 130 K; (b) 155 K; (c) 170 K; (d) 180 K; and (e) 210 K. (Source: Recrystallization mechanism for the grain refinement in undercooled DD3 single-crystal superalloy)
Most people seem to be unaware that China has been building DD3 nickel-based single-crystal superalloys for about twenty years.
The indigenous WS-10 turbofan engine project started in 1986. By 1992, the "first test engine [was] completed and bench testing began." Therefore, we can deduce China was probably building DD3 single-crystal superalloys a few years prior to 1992.
The earliest English citation (see article below) that I found for China's DD3 single-crystal superalloy was in 1995. Also, the earliest English citation that I found for China's DD6 second-generation single-crystal superalloy was in 2003.
The point of these citations is to match the known dates for China's DD3 and DD6 single-crystal superalloys with the known dates for China's first tests of the WS-10 and WS-15 turbofan engines. They match almost perfectly.
China was building DD3 nickel-based single-crystal superalloys by the late 1980s or early 1990s and the indigenous WS-10 engine was tested in 1992.
Also, GlobalSecurity reported that China successfully tested its WS-15 engine prototype in 2005. Based on the citation, we can place the approximate date of China's manufacture of DD6 nickel-based single-crystal superalloys around the early to mid-2000s.
The timeline for the DD3 and DD6 superalloys fits the dates for testing the WS-10 and WS-15 turbofan engine prototypes.
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Advanced Performance Materials, Volume 2, Number 3 - SpringerLink
"Advanced Performance Materials
Volume 2, Number 3 (1995), 217-229, DOI: 10.1007/BF00705445
Some recent developments of advanced titanium alloy and nickel base superalloys in BIAM
M. G. Yan, Y. F. Han, C. X. Cao and Z. T. Wu
Abstract
A brief review of recent research and development works of some advanced Ti alloys and Ni base superalloys in the Institute of Aeronautical Materials, Beijing (BIAM) is reported. In which, the tensile deformation and fracture characteristics in an agr-beta Ti alloy, the creep behavior of Ti3Al intermetallic alloy and effect of heat treatment and crystal orientation on the creep properties of a single crystal Ni base alloys DD3, are presented. The applications of the above mentioned alloys in aeronautic industry are described.
Mechanisms of Low Cyclic Fatigue of DD6 Alloy at Elevated Temperature--
"《Journal of Aerospace Power》 2003-06
Mechanisms of Low Cyclic Fatigue of DD6 Alloy at Elevated Temperature
LI Ying, SU Bin (Beijing Institute of Aeronautical Materials, Beijing 100095, China)
Low cycle fatigue mechanism of a single crystal nickel-base superalloy,DD6,has been investigated at 760℃ and 980℃. It was found that there were two kinds of sites where crack initiates, one being the surface of the specimens and the other being the sub-surface. Microcracks and oxide layer on the specimen surface are potential crack initiation sites in this superalloy. Secondary crack,reared ridge, and microcrack in the front of the main crack tip can all hinder crack propagation during low cycle fatigue.
【Key Words】： aerospace propulsion system single crystal superalloy low cycle fatigue crack initiation crack propagation
【CateGory Index】： V232
【DOI】： CNKI:SUN:HKDI.0.2003-06-005"
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