L605(UNS R30605) cobalt-based superalloy (marketing department of Shanghai HY Industry Co., Ltd)

L605(UNS R30605) is a cobalt-based superalloy containing large amounts of chromium and tungsten. It is characterized by excellent high temperature strength up to 1500°F (1093°C), maximum temperature in corrosive environments up to 2000°F (1093°C), excellent resistance to oxidation, sulfide wear and wear resistance. L-605 has other lesser-known qualities, such as high ductility and biocompatibility. L-605 is nonmagnetic, which means that, like most other superalloys, it loses ductility when exposed to intermediate temperatures for prolonged periods of time.

The service temperature of L605 alloy is between 649 and 927°C, and by optimizing the composition and controlling the content of γ’ in the alloy, the L605 alloy has good creep strength, thermal stability and excellent processability and welding performance .

For most nickel-based alloys, some deficiencies in performance limit their application in A-USC units. For example, R-41 and Waspaloy alloys have high strength, but poor processability, especially welding performance, while alloys such as X-750 are just the opposite. However, L605 alloy has become one of the important candidate materials for A-USC unit due to its good comprehensive performance.

L605 (UNS R30605) executive standard

L605(UNS R30605) Material grades and equivalents: Udimet alloy L605; Alloy L605; Cobalt alloy L605; Haynes 25; UNS R30605; KC20WN; WF-11; AIS1670; GH5605; HS25; 

Co – Cr Alloy L605 Tube for Coronary Stent

At the Washington Interventional Cardiac Medicine Summit in October 2005, people generally agreed on the benefits and safety profile of drug stent therapy; but at the same time, it was found and reported that there was an increased risk of fatal thrombosis in patients with drug-eluting stent implantation, Although only 0.5% ~ 1.3% of the proportion, which to some extent increased people’s safety concerns after drug-eluting stent implantation.

At present, the development goal of the next-generation stent is to use a new generation of materials: bare stents such as L605, or to develop replacement products for existing drug-coated stents, or to develop biodegradable drug stents. All of these put forward higher requirements on the materials and manufacturing technology of stents. Some device properties are directly related to materials, such as biocompatibility, X-ray and NMR visual properties, radial support strength, rebound properties, axial Compliant characteristics in the direction and radial direction, conveying characteristics, cross-sectional area characteristics, etc.
Ideal stent materials should be fully corrosion-resistant, biocompatible, fatigue-resistant, and have good X-ray and MRI visualization properties. For balloon-expandable stents, when expanded, high tensile strength is beneficial to obtain high radial support strength with extremely small external implant material volume, and narrower strut width can also be used in smaller cross-sections , which improves compliance, delivery characteristics, and facilitates delivery to finer vascular regions.

In order to deploy the stent under a suitable balloon pressure, the material tends to be selected with a lower yield strength, while the steep work hardening rate makes the strength increase when the stent expands, and the elongation must be high enough to withstand the ball Deformation of the balloon when it expands, these are interrelated, and some are contradictory, and must be carefully balanced, such as using a high yield strength to increase radial support strength, and at the same time promote rapid rebound when the balloon is deflated, and then The latter is unfavorable, fine grains will increase the fatigue life and improve the polishing effect, but will increase the yield strength and produce additional immediate springback.

The development history of Co-Cr alloys as coronary stent materials: As implant materials, Co-Cr alloys have a long history of application in dentistry, orthopedics and cardiovascular departments. Early blood-contact applications included pacemaker connectors, venous thrombosis filters, abdominal aortic stents, and self-expanding stents. These alloys are used because of their combination of long-proven biocompatibility properties and high strength in the cold-worked state. The application of Co-based alloys in expandable stents has recently grown rapidly. As introduced in the 2004 European Euro-PCR material catalog, there are 6 companies developing its application in coronary stents. Guidant believes that laser cutting the stent on the super Co-Cr alloy can reduce the width of the strut and the volume of the whole stent without reducing the radial support strength and ray visibility, and the result is an extraordinary achievement. Delivery properties and unprecedented clinical effects.

Applicability of Co-Cr alloy L605 as a stent: Starting from an ideal balloon-deployable stent material, the properties of the selected alloys were compared. Because the Co-Cr alloy has a high density, it is beneficial to ray visibility: and the high tensile strength characteristics allow the stent width to be designed to be narrower, which will form a smaller stent cross-sectional area and stent volume, and improve Improvements in compliance and delivery properties, which in turn allow stents to be implanted in smaller vessels, have been demonstrated by companies making new-generation stents from Co-Cr alloys. With the change in the material used for stents from stainless steel to Co-based alloys, the width of stent struts was significantly reduced, and these new stents also demonstrate narrower strut widths than those on the currently market-dominating 316L stents.

Comparison of L605 with several other grades of Co-Cr alloys: The main alloys used in balloon-expandable stents that have been tested are alloys with more commonly known commercial names: L605, MP35N and Phynox/Elgiloy, Phynox and Elgiloy is in the same grade in both ASTM and ISO standards. In actual production the ingot is smelted to a single composition, meeting the requirements of both specifications. The mechanical properties mentioned above are after cold working and annealing, and the ASTM grain size is grade 7 or smaller typical values. As the width of stent struts decreases, the requirement to pursue finer grain size materials becomes more important. As the most basic principle, there must be at least 3 levels of crystal grains across the width direction of the struts. The density, elastic modulus and mechanical properties of these three Co-Cr based materials are significantly higher than those of 316L. These alloys are non-ferromagnetic and therefore safe for NMR. The literature proves that the Artifacts of Co-Cr alloy stents are lower than those of stainless steel stents. Under the condition that the tensile properties of these three Co-based alloys are comparable, L605 has a superior high density and high E, and the stents manufactured therefrom have the advantages of better ray visibility and less springback characteristics. This is the reason why L605 in Co-Cr alloy has more commercial applications.

Sensitivity to process parameters and optimization of required properties: To ensure reproducibility and uniformity of tube properties, control of the tube drawing process is required. 316L shows moderate sensitivity to processing parameters: while L605 is more difficult to control, its properties vary in a wide range according to the processing process, which provides an opportunity to meet the material properties required for different medical device manufacturing, provided that the tube manufacturer is adequate. Understand the behavior of materials and precisely control the pipe processing process; and the bracket designer must have sufficient understanding of this and reasonable material selection. L605 is also particularly sensitive to heat treatment. According to the heating temperature and time provided by the pipe supplier, someone studied the annealing behavior of the pipe with a cold working amount of 35%. When making small brackets or struts, the grain diameter cannot be too large. therefore. When selecting tubing for the manufacture of different stent products, clear grain size requirements should be addressed.Minitubes conducted experiments and analyzes of the sensitivity of L605 processing parameters to performance in relation to scaffold behavior, showing the importance of controlling processing parameters. The literature discusses the design of stents and their behavior, arguing that the design of medical devices depends on the optimization of material properties. For the design where the deformation of the strut is mainly concentrated at the flexible connection and has a small springback, it is necessary to increase the stress corresponding to the strain as much as possible; on the contrary, for the design of the support that emphasizes small springback, it is necessary to seek lower stress materials. For example, the hot-rolled tube billet of L605 has an outer diameter of 30 mm and a wall thickness of 3 mm, and is cold-drawn into a pipe with an outer diameter of 2.0 mm and a wall thickness of 0.12 mm. % cold drawing deformation, and then annealed at 4 different temperatures for 10 min. Compared with 316L, L605 has a wider range of performance to match bracket applications.

Microstructure of L605 alloy: After various drawing steps of L605 pipe, optical microstructure analysis and scanning electron microscope analysis show that the hot-rolled tube billet is twinned austenite grains, and the cross-section presents uneven grains. Grain size, after cold working and annealing, the grain size decreases rapidly, and the size uniformity is also improved. After 15 passes, a typical stent tubing size is finally obtained with a uniform equiaxed grain distribution, the grain size of which depends on the processing parameters. Scanning electron microscope photos show that the final annealed tubes present evenly distributed point balls on the matrix, and their size is as large as 1 um. The energy spectrum analysis of point balls shows that they have high W content. Therefore, the final polishing quality of the L605 bracket is more stringent than that of the 316L bracket.

L605(UNS R30605) Chemical composition:

L605(UNS R30605) Physical properties:

L605(UNS R30605) sheet mechanical properties in the room temperature:

L605 (UNS R30605) solution treatment: Most of the delivery state of L605 is a solid solution state, and the performance is optimal in this state. The material has a solution temperature range of 2150-2250°F followed by rapid air cooling or water quenching; sheet thickness up to 0.025″ has a solution temperature of 2150°F followed by rapid air cooling or water quenching; sheet thickness over 0.026″ is solution The temperature is 2200°F, followed by rapid air cooling or water quenching; the solid solution temperature of plate is 2200°, followed by water quenching; the solution temperature of bar stock is 2250°F, followed by water quenching.

L605(UNS R30605) Corrosion Resistance: L605 exhibits excellent resistance to high temperature corrosive gases in jet engine applications. Oxidation resistance to 1600°F intermittent duty and 2000°F continuous duty is also very good. During heating, L605 is highly resistant to oxidation without material spalling. At the same time, the material is resistant to a variety of chemical oxidants, especially hydrochloric acid and nitric acid at a certain concentration and temperature, and has a good resistance to salt spray corrosion.

L605(UNS R30605) Thermal Stability: When exposed to moderate temperatures for prolonged periods of time, L-605 exhibits approximately the same loss of room temperature ductility as some other solid solution strengthened superalloys such as HASTELLOY X or INCONEL 625. Due to the precipitation of deleterious phases, in the case of alloy L-605, the phase in question is the CO2WLaves phase.

L605(UNS R30605) processing performance: The strength of L-605 benefits from the solid solution strengthening of tungsten in the first phase and the solid solution strengthening of precipitated carbides in the second phase. L-605 is characterized by good formability and machinability, it can be easily forged and hot-worked between 1900°F and 2300°F (1038°C to 1260°C), or under bending, rotating and stretching Do cold work. However, this superalloy hardens very quickly during work, and to mitigate this we recommend routine annealing at intermediate temperatures, especially if the end piece is very complex.

L605(UNS R30605) welding process: L-605 can be easily welded by standard methods such as argon tungsten arc welding, gas metal arc welding, manual arc welding, electron beam welding and resistance spot welding, submerged arc welding is not recommended Process for welding. It is recommended to use good joint equipment, minimum braking current, low interlayer temperature for welding, and rapid cooling after welding.

L605 (UNS R30605) Field of application: L605 Due to all its characteristics, L-605 can be used in aerospace industry. It is mainly used in the manufacture of gas turbine engine components, especially those often subjected to high temperatures, including rings and blades for turbines, and combustor components (combustor liners).
In addition to the aerospace industry, L-605 is used in land-based gas turbines in power plants, and in industrial furnaces for muffle furnaces and linings in high-temperature kilns. L-605 can also be used to make high temperature ball bearings and bearing races, this high temperature alloy can also be used for parts in corrosive environments, mainly wet chlorine, hydrochloric and nitric acids. Due to its biocompatibility, L-605 can also be used in the medical industry, mainly for the manufacture of heart valves, dental and orthopedic medical devices. For these parts, a special recrystallization process must be used to control the grain size for strength and ductility.

Shanghai HY Industry Co., Ltd has international first-class material production equipment such as high temperature alloy isothermal forging production line, CONSARC vacuum melting furnace, VAR vacuum arc remelting furnace etc., with strong professional ability and highly responsible management team. We are a member of China Application of nuclear energy materials, Member of the International Council of the Aeronautical Sciences. Years of experience in Corrosion Resistant Alloy & Superalloy. When you have superalloy material inquiry, please contact us without hesitation. Shanghai HY Industry Co., Ltd is Corrosion & fatigue nickel alloy professional manufacturer,We will provide you with sincere and thoughtful service.

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