EP0171336B1 - Acier inoxydable austenitique au cobalt ultra résistant à la cavitation érosive - Google Patents

Acier inoxydable austenitique au cobalt ultra résistant à la cavitation érosive Download PDF

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Publication number
EP0171336B1
EP0171336B1 EP85420115A EP85420115A EP0171336B1 EP 0171336 B1 EP0171336 B1 EP 0171336B1 EP 85420115 A EP85420115 A EP 85420115A EP 85420115 A EP85420115 A EP 85420115A EP 0171336 B1 EP0171336 B1 EP 0171336B1
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EP
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Prior art keywords
stainless steel
containing stainless
steel alloy
cavitation
weight
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
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EP85420115A
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German (de)
English (en)
French (fr)
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EP0171336A1 (fr
Inventor
Raynald Simoneau
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Hydro Quebec
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Hydro Quebec
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/30—Ferrous alloys, e.g. steel alloys containing chromium with cobalt

Definitions

  • the present invention relates to an austenitic cobalt stainless steel having a very high resistance to high intensity erosive cavitation making it very particularly useful for the manufacture or repair of parts of hydraulic machines.
  • the invention also relates to the parts of hydraulic machines thus made or covered with said cobalt stainless steel.
  • cavitation phenomenon in particular experienced by hydraulic machines such as turbines, pumps, propellers, valves, or exchangers, is a drawback well known to specialists.
  • cavitation phenomenon the phenomenon by which a cavity or a bubble of vapor is formed in a liquid when the local pressure drops below the vapor pressure. When the pressure rises above that of the vapor, the gas or vapor bubble suddenly implodes. This implosion is accompanied by powerful physical phenomena, in particular a microjet which follows the bubble and whose speed can reach the values of several hundreds of meters per second.
  • the best solution consists in using parts entirely made of stainless steel. Another solution is to weld one or more layers of stainless steel on all the surfaces of the carbon steel parts subject to cavitation phenomena of low intensity to thereby avoid the synergistic effect of cavitation erosion and galvanic corrosion.
  • austenitic stainless steels essentially consisting of approximately 15.0% to 18.5% by weight of chromium, from approximately 10% to approximately 22.5% by weight of cobalt, up to approximately 0, 2% by weight of carbon up to approximately 1.5% by weight of manganese up to approximately 0.75% by weight of silicon, up to approximately 0.15% by weight of nitrogen, the balance being iron .
  • DE-C-607 384 describes iron-chromium-cobalt alloys which contain less than 0.3% of carbon, from 15 to 22% of chromium, from 6 to 16% of manganese, from 1 to 10% of cobalt, the the remainder consisting of iron accompanied by the usual impurities.
  • the present invention is directly related to the discovery that low hardness cobalt stainless steels containing as little as 8% by weight of cobalt have an erosive cavitation resistance as good as that of alloys containing up to '' at 65% cobalt, provided that at least 60% by weight of said stainless steels with low cobalt content is, at room temperature, in a cubic phase with a metastable centered face having a sufficiently low stacking fault energy therein so that it can transform under the effect of cavitation into a compact hexagonal phase s and / or into martensite a showing a fine jaw 'deformation.
  • the present invention has for its first object an austenitic cobalt stainless steel having a high resistance to erosive cavitation, of the type consisting of: the remaining percentage consisting of Fe and the usual impurities, said steel being characterized in that its content of elements known as ferritizing agents (Cr, Mo, Si), in elements known as austenitizing agents (C, N, Co, Ni, Mn) and, among these ferritating and austenitic elements, in elements known to increase or decrease the energy of stacking fault, is suitably chosen and adjusted so that at least 60% by weight of the steel is, at the ambient temperature, in a cubic phase with a metastable centered face y having a sufficiently low stacking energy that it can transform under the effect of cavitation into a compact hexagonal phase E or into martensite a showing a end deformation chewing.
  • ferritizing agents Cr, Mo, Si
  • austenitizing agents C, N, Co, Ni, Mn
  • Co stainless steel according to the invention has a low carbon content (less than 0.3%).
  • the fact that this steel also has a excellent resistance to cavitation despite this low carbon content is compatible with the above-mentioned result of observations made by KC Anthony and AI, namely the observation that the high resistance to cavitation of STELLITE-6 type alloys is retained even if the carbon content of these alloys is reduced from 1.3 to 0.25%.
  • At least 60% by weight of the cobalt stainless steel according to the invention must be, at ambient temperature, in a cubic phase with a centered face which is both metastable and has the lowest possible energy. lack of stacking.
  • the metastability of the face-centered cubic austenitic phase therein is an essential element of the invention, since it is absolutely necessary that the steel is capable, under the effect of cavitation, of being transformed into a compact hexagonal phase e and / or martensite a.
  • phase y the content of the steel in known ferritating (Cr, Mo, Si) and austenitic (C, N, Co, Ni, Mn) elements respectively must be properly selected and adjusted so as to just stabilize the austenite (that is to say the y phase) in particular in the case of rapid cooling of the steel, to promote a transformation induced by cavitation of this y phase into the ⁇ and / or martensite phase .
  • the stainless steel according to the invention must show a fine cavitation-induced chewing, which chewing is specific to crystals with a low energy of stacking fault.
  • the elements known to increase the energy of stacking fault one can quote Ni and C.
  • those known to lower the EFE one can - quote Co, Si, Mn and N. Of course, these last elements will have to be chosen in priority to obtain the desired result, namely a low EFE.
  • Cobalt is undoubtedly one of the most interesting insofar as it has the advantage, in addition to lowering EFE, to maintain the metastability of the austenitic phase of steel over a large concentration range.
  • the stainless steel according to the invention which contains less than 30% by weight of cobalt and up to 70% by weight of iron can thus have a stacking fault energy as low as that of alloys with a high cobalt content, and a substantially identical end-of-deformation coupling (see in particular the article by DA Woodford et al, “A deformation Induced Phase Transformation Involving a Four-Layer Stacking Sequence in Co-Fe Alloy ", Met. Trans., Vol. 2, page 3223, 1971 where it is stated that in Fe-Co alloys, only 15% by weight of iron is sufficient to make completely disappear the transformation induced by cavitation from phase y to phase e).
  • chromium has a very strong interaction with cobalt and iron to promote the formation of low energy crystals due to stacking failure.
  • the surface layer of the Fe-Cr-Co-C alloys according to the invention shows, after exposure to cavitation, a very fine latticework network in the compact hexagonal phase (phase e) or martensite a.
  • phase e the compact hexagonal phase
  • martensite a The presence of this fine and continuous chewing obtained under exposure to cavitation explains the high resistance to cavitation of the alloy, which, by its chewing, has an effective means of absorbing the energy of cavitation shocks by deformation of its crystal structure.
  • This fine chewing is also an excellent means of accommodating high stresses and thus delaying the creation and propagation of fatigue cracks.
  • the localized hardening associated with this fine chewing ensures an extension of the chewing to the whole exposed surface at the beginning of the exposure to cavitation (incubation period).
  • the austenitic cobalt stainless steel according to the invention advantageously consists of: the remaining percentage consisting of Fe and the usual impurities.
  • a particularly interesting stainless steel covered by this preferred embodiment is that consisting of 10% by weight of Co, 18% by weight of Cr, and 0.3% by weight of C, the remaining percentage consisting of Fe and usual impurities. It turns out that this particular steel is not only very effective, but one of the cheapest. It can in particular be noted that the composition of this steel is substantially equivalent to the composition of stainless steels of the standard 300 series, the only difference residing in the absence of nickel (known to increase the energy of EFE stacking fault) replaced by an increased amount of Co (known to lower EFE).
  • the austenitic cobalt stainless steel according to the invention advantageously consists of: the remaining percentage consisting of Fe and the usual impurities.
  • Co stainless steel according to the invention is soft. This steel is less expensive than conventional alloys with a high Co content such as STELLITE 6 or STELLITE 21, while having substantially the same resistance to cavitation. As a result, the stainless steel according to the invention offers an economical alternative to alloys of the STELLITE 21 type currently used to protect hydraulic machines against the effects of erosive cavitation. Welding wires or electrodes made from the steel according to the invention can be used to repair damage due to cavitation. Hydraulic machine parts or whole groups can also be cast or completely covered with this steel which is cheaper than the Stellite is capable of being hot and cold rolled for the development of the manufacture of machine elements hydraulic with high resistance to cavitation.
  • another subject of the invention is the use of the steel according to the invention for the manufacture or recovery of parts intended for the manufacture or repair of hydraulic machines as well as the manufacture of wires welding for the manufacture or repair of hydraulic machines.
  • the stainless steel parts according to the invention have a cavitation resistance at least equal to the parts made of harder alloys of the STELLITE-1 or -6 type. Since the stainless steels according to the invention are soft, they are much easier to grind. In fact, the parts according to the invention have all the advantages of parts made from soft alloys with a high Co content, of the STELLITE-21 type, but at a lower cost.
  • the resistance of the steels and alloys tested to erosive cavitation was measured by ultrasonic cavitation test according to standard ASTM-G32.
  • the losses in weight of 16 mm cylindrical samples vibrating at 20 kHz at a double amplitude of 50 ⁇ m in distilled water at 22 ° C were measured every half hour for six hours using a electric scale accurate to tenth of a milligram.
  • the materials tested are listed in Table 1 below, where their composition is also found. nominal, their manufacturing process, their hardness and their original crystallographic structure.
  • the experimental Co # 1 Co # 25 alloys listed in the previous table were prepared by melting on a water-cooled copper plate in a small laboratory arc furnace an appropriate mixture of several of the following constituents: steel carbon, 304 stainless steel, STELLITE-21, ferrochrome, electrolytic cobalt, ferromanganese and ferrosilicon. It should be noted that the compositions of these experimental alloys, with the exception of Co # 7,12 and 15 which were tested for reference, all fall within the composition range of cobalt stainless steel according to the invention.
  • Metallographic observations were made by taking optical and electron micrographs on the eroded surfaces of the samples after various periods of exposure to cavitation.
  • the surfaces of the samples in question were originally electrochemically polished and cleaned with acid.
  • microhardness measurements were carried out by applying a pyramidal diamond to the eroded surface of the samples after various periods of exposure to cavitation, until this surface was too bumpy to allow measurements.
  • the longest wavelength CuK " has been chosen so that the diffraction occurs only on a thin surface layer (of the order of 10 to period d incubation so that surface erosion has just started.
  • Table 1 as well as Figures 1 and 2 provide the results of the erosive cavitation tests carried out by the Inventor. These results clearly demonstrate that stainless steel 308 has a resistance to cavitation twice that of carbon steel 1020 and that all of the experimental Co-Cr-Fe alloys with the exception of Co # 5, 7 and 11 to 15 have a much better resistance to cavitation (of the order of 10 to 50 times greater) than stainless steel 308 although they have only a slightly higher hardness.
  • the table above shows that the 1020 carbon steel sample is the only material which did not show any phase transformation induced by deformation after exposure to cavitation. As expected, only a small portion of the eroded surface of the austenitic 308 stainless steel sample was transformed into martensite. It is interesting to note that on this steel, the exposure to cavitation modified the texture of the surface by eroding the oriented surface grains (200), the oriented grains (111) showing superior resistance.
  • Stainless steel 301 which was partially martensitic when welded, had its surface completely transformed into martensite under the effect of cavitation.
  • the alloy Co # 5 (10% cobalt) which was essentially ferritic when melted with a small percentage of austenite, was almost completely transformed into martensite under exposure to cavitation.
  • the alloy Co # 3 (20% cobalt) which was austenitic when melted, was transformed superficially into the compact hexagonal phase ⁇ , with a small percentage of martensite, while the surface of the sample in STELLITE 21 was transformed from less important in ⁇ phase only.
  • the Co # 6 alloy (10% cobalt, 18% chromium) has shown excellent resistance to cavitation with an induced transformation into martensite a rather than in phase E.
  • the alloys Co # 11 to 15 which were martensitic in the state as cast (see Table 1), did not show the best resistance to cavitation.
  • the degree of transformation induced by cavitation follows the following increasing order: 1020 (approximately 0%), Co # 5 (approximately 10%), 308 (approximately 15%), 301 (approximately 75%) STELLITE 21 (approximately 75%), Co # 3 (approximately 90%), Co # 6 (approximately 90%).
  • the hardening induced by cavitation follows substantially the same order.
  • FIG. 16a shows that there is a significant increase in the surface hardness of the most resistant alloys during the incubation period. No strain hardening was measured on the soft ferrite of the carbon steel sample.
  • the experimental alloy Co # 3 which, when melted, is softer than STELLITE 21, showed the strongest hardening, with a final hardness higher than that of STELLITE 21. This hardness increased very quickly at the beginning of the period of 'incubation.
  • microhardness at depth shows that the hardening by deformation due to cavitation is limited to a very thin surface layer (less than 50 wm), which makes this kind of measurement very difficult.
  • the Co # 3 alloy (20% cobalt) exhibits a phase transformation induced by cavitation as well as a more pronounced work hardening than STELLITE 21 (65% cobalt) which is known to be very stable.
  • This Co # 3 alloy also appears to have a resistance on the upper cavitation, even if this alloy has a lower initial hardness (23 RC compared to 30 RC for STELLITE 21).
  • the composition that stainless steels must have to offer the best possible resistance to cavitation can include various hardeners such as molybdenum, to maintain the same degree of phase transformation.
  • the content of the cobalt stainless steel according to the invention in elements known as ferritisants (Cr, Mo, Si) and austenitisants (C, N, Co, Ni, Mn) must be appropriately chosen and adjusted so as to barely stabilize the austenite, particularly in the case of rapid cooling, to thus promote a transformation induced by cavitation from phase a to phase ⁇ or to martensite , the high resistance to cavitation of the steels according to the invention resulting mainly from their composition where the elements known to increase the stacking fault energy, namely carbon and nickel, are replaced as much as possible by known elements to lower this stacking fault energy such as Co, Si, Mn and N and thus lead to a finer deformation coupling.
  • ferritisants Cr, Mo, Si
  • austenitisants C, N, Co, Ni, Mn
  • the cobalt stainless steels according to the invention can advantageously be used for the manufacture and repair of parts or groups of hydraulic machines, such as turbines, pumps, valves, etc. They can be used either as covers welded to carbon steel, or as basic materials, cast or in the form of sheet metal, for the manufacture of machines made of stainless steel. These steels can furthermore be hot or cold rolled and be developed in welding wires or electrodes to replace the much more expensive STELLITE 21 used to repair cavitation damage in hydraulic turbines.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Hydraulic Turbines (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
  • Materials For Medical Uses (AREA)
  • Laminated Bodies (AREA)
  • Metal Extraction Processes (AREA)
EP85420115A 1984-06-28 1985-06-24 Acier inoxydable austenitique au cobalt ultra résistant à la cavitation érosive Expired EP0171336B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CA457755 1984-06-28
CA000457755A CA1223140A (fr) 1984-06-28 1984-06-28 Acier inoxydable austenitique au cobalt ultra resistant a la cavitation erosive

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EP0171336A1 EP0171336A1 (fr) 1986-02-12
EP0171336B1 true EP0171336B1 (fr) 1988-08-17

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EP85420115A Expired EP0171336B1 (fr) 1984-06-28 1985-06-24 Acier inoxydable austenitique au cobalt ultra résistant à la cavitation érosive

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US (1) US4588440A (es)
EP (1) EP0171336B1 (es)
JP (1) JPS6115949A (es)
KR (1) KR860000402A (es)
CN (1) CN85104938A (es)
AT (1) ATE36561T1 (es)
BR (1) BR8503121A (es)
CA (1) CA1223140A (es)
DE (1) DE3564452D1 (es)
ES (1) ES8609500A1 (es)
NO (1) NO852315L (es)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1269548A (fr) * 1986-06-30 1990-05-29 Raynald Simoneau Acier inoxydable austenitique au cobalt ultra resistant a la cavitation erosive
DE3736965A1 (de) * 1987-10-31 1989-05-11 Krupp Gmbh Hochfeste stickstoffhaltige vollaustenitische cobalstaehle mit 0,2-dehngrenzen oberhalb 600 n/mm(pfeil hoch)2(pfeil hoch)
US5288347A (en) * 1990-05-28 1994-02-22 Hitachi Metals, Ltd. Method of manufacturing high strength and high toughness stainless steel
US5514329A (en) * 1994-06-27 1996-05-07 Ingersoll-Dresser Pump Company Cavitation resistant fluid impellers and method for making same
US5514328A (en) * 1995-05-12 1996-05-07 Stoody Deloro Stellite, Inc. Cavitation erosion resistent steel
FR2761006B1 (fr) * 1997-03-21 1999-04-30 Usinor Roue pour vehicule automobile
US6589363B2 (en) * 2000-12-13 2003-07-08 Eaton Corporation Method for making heat treated stainless hydraulic components
EP1540024A1 (en) * 2002-09-16 2005-06-15 BorgWarner Inc. High temperature alloy particularly suitable for a long-life turbocharger nozzle ring
US7162924B2 (en) * 2002-12-17 2007-01-16 Caterpillar Inc Method and system for analyzing cavitation
US9597988B2 (en) 2009-11-16 2017-03-21 Johnson Controls Technology Company Method of laser welding TWIP steel to low carbon steel
US10281903B2 (en) * 2015-07-27 2019-05-07 Hitachi, Ltd. Process for design and manufacture of cavitation erosion resistant components
CN105842308A (zh) * 2016-03-25 2016-08-10 华南理工大学 一种消除Super304H钢晶间腐蚀敏感性的方法
CN113817969B (zh) * 2020-06-19 2022-09-27 香港大学 一种高强度超耐腐蚀无磁不锈钢及其制备方法

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Also Published As

Publication number Publication date
JPS6115949A (ja) 1986-01-24
JPH0542495B2 (es) 1993-06-28
NO852315L (no) 1985-12-30
EP0171336A1 (fr) 1986-02-12
ES544717A0 (es) 1986-07-16
KR860000402A (ko) 1986-01-28
ATE36561T1 (de) 1988-09-15
US4588440A (en) 1986-05-13
CA1223140A (fr) 1987-06-23
CN85104938A (zh) 1987-01-07
ES8609500A1 (es) 1986-07-16
BR8503121A (pt) 1986-03-18
DE3564452D1 (en) 1988-09-22

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