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WO2011029164A1 - Superalliage à base de nickel pour soupape de moteurs à combustion interne - Google Patents

Superalliage à base de nickel pour soupape de moteurs à combustion interne Download PDF

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Publication number
WO2011029164A1
WO2011029164A1 PCT/BR2009/000293 BR2009000293W WO2011029164A1 WO 2011029164 A1 WO2011029164 A1 WO 2011029164A1 BR 2009000293 W BR2009000293 W BR 2009000293W WO 2011029164 A1 WO2011029164 A1 WO 2011029164A1
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Prior art keywords
alloys
mass
internal combustion
alloy
combustion engine
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Ceased
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PCT/BR2009/000293
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English (en)
Portuguese (pt)
Inventor
Celso Antonio Barbosa
David Delagostini Jarreta
Alexandre Sokolowsky
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Villares Metals SA
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Villares Metals SA
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Priority to PCT/BR2009/000293 priority Critical patent/WO2011029164A1/fr
Publication of WO2011029164A1 publication Critical patent/WO2011029164A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/03—Alloys based on nickel or cobalt based on nickel
    • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium

Definitions

  • the present invention deals with a precipitation hardened Ni-Fe-Cr superalloy for application to internal combustion engine valves, having as main characteristics the precipitation of Ni 3 (AI, Ti, Nb) and niobium and titanium carbides in their microstructure.
  • the alloy design based on its microstructural aspects, allows the alloy of the present invention to have equivalent or superior properties to alloys used in internal combustion engine valves, associated with significant reduction in alloy cost due to lower nickel content. .
  • the alloy of the present invention is intended for the manufacture of valves, which application requires of the alloy a need for various properties, namely: oxidation resistance, wear resistance and heat resistance, given the high temperatures involved in the application.
  • Inconel 751 An example of an alloy with excellent performance in these applications is Inconel 751, which has a very high cost due to its high nickel content above 70%. In this sense, lower nickel alloys with properties of hot strength, corrosion resistance, long term microstructural stability and abrasion resistance have been developed. Examples are prior art alloys, NCF3015 (JIS3015D - US Patent 5,660,938) and HI 461 alloy.
  • Oxidation resistance at elevated temperatures is the property to be evaluated in terms of corrosion, based on the good performance of Inconel 751.
  • the alloys of the present invention meet all these needs.
  • Ni-Fe-Cr alloys used in exhaust valves are closely related to the presence of intermetallic phases, alloying elements and carbides in their microstructures.
  • Intermetallic phases are very important for high temperature resistance.
  • a composition that gives the material the corrosion resistance required in the medium of use is very important.
  • carbides is important for the abrasion resistance of the material.
  • the performance of alloying elements in the formation of these phases has been carefully analyzed and modified in relation to the traditional concept.
  • the present invention utilizes the use of relatively high amounts of niobium (higher than prior art alloys) as an alloying element, not only as a carbide former, but mainly as a fine intermetallic precipitate.
  • Another element that the present invention utilizes in higher amounts than prior art alloys is aluminum, which has the preponderant niobium-forming function of the niobium, Ni 3 (AI, Nb), improving the heat resistance of the alloy. material.
  • aluminum acts to improve the hot oxidation resistance of the alloy.
  • the morphology of these precipitates is determined by the surface energy of the ⁇ / ⁇ ' interface and the elastic energy generated by the misalignment of the ⁇ and ⁇ ' lattices, being determined primarily by the lattice deformation. If this strain is small, the morphology that will minimize surface energy and volume strain energy will be the spherical. However, if the lattice deformation is considerably large, the morphology of the precipitates will not be spherical but cubic. When the lattice mismatch is up to 0.02% the ⁇ ' precipitates are spherical, in the case of mismatch between 0.5 and 1.0% these precipitates are cubic, and above 1.25% assume platelet shape.
  • Niobium presents a lower precipitation kinetics of the ordered Ni 3 Nb phase than when compared to elements such as titanium and aluminum in the Ni 3 phases (Ti, AI).
  • high levels of niobium lead to precipitation of the ordered phase ⁇ " (Ni 3 Nb), similar to phase ⁇ ' .
  • niobium When added to the alloy at lower levels, niobium only increases the volume of precipitates gamma line and the solubilization temperature of this phase, bringing its hardening effect to even higher temperatures.
  • alloy element compositions which, by weight percentage, consist of:
  • 0.1 to 4.0 aluminum preferably 1.0 to 3.0 aluminum, typically 2.0% aluminum.
  • non-metallic impurities include, but are not limited to, the following elements, by weight:
  • Chromium is used to give the alloy resistance to corrosion and oxidation at high temperatures, so its content should be greater than 10% for exhaust valve superalloys. Content above 25% threatens the stability of the microstructure due to the tendency of formation of phases such as the sigma phase and alpha line ( ⁇ and ⁇ '), which deteriorate the ductility. Thus, it was decided that the chromium content of the alloys would be between these limits, preferably between 14.0% and 22.0%, typically 18.0%.
  • Titanium and niobium are carbide formers. When added to the alloy, they first combine with carbon, given the high chemical affinity of these elements. Formed carbides contribute to abrasive wear resistance. The titanium and niobium content not combined with carbon is combined with nickel to form the intermetallic phases ⁇ 'and ⁇ ".
  • titanium and niobium contents should be added to the alloy of the present invention according to the relationship , Nb + 2 Ti, which accounts for the atomic mass difference of the two elements, so for the desired effect on wear resistance and heat resistance properties, the Nb + 2Ti ratio should be greater than 4.0% and preferably higher. at 5.0%, typically equal to 8.0%.
  • MC-type niobium carbides are more effective in abrasion resistance than titanium because of their higher hot hardness.
  • the niobium content must be carefully balanced against the carbon content. Since niobium has a greater tendency to bond to carbon, the niobium available for nickel intermetallic phase formation will be the amount of this element dissolved in the alloy matrix after reaction with carbon to form the primary carbides. : C must be greater than 7.4: 1 (by mass) so that there is still dissolved Nb in the austenitic matrix which will precipitate as Ni 3 Nb.
  • a for the element Nb is between 2.0 and 8.0% (by mass), with an intermediate range of 3.0 to 8.0% (by mass) of Nb and a narrow range of 3.1 to 8.0. % (by mass) Nb, or even narrower from 3.5 to 8.0.
  • Nb In addition to improvements in heat and abrasion resistance, Nb also improves weldability of the ⁇ "phase precipitation hardened superalloys, and furthermore improves corrosion resistance in sulfating environments such as diesel engines.
  • Nb can be partially replaced by tantalum (Ta) in equiatomic bases.
  • Ta tantalum
  • Ta is also an intermetallic phase former with nickel and strongly stabilizes primary carbides, being equally beneficial for hot hardness and abrasion resistance.
  • niobium showed effect on the heat resistance properties.
  • the mechanism is not fully defined, in the alloys of the present invention the niobium content not combined with carbon should form different intermetals than titanium intermetallics, probably of the two-line gamma ( ⁇ ") type, very stable to coalescence and thus , effective in improving the properties of high temperature strength
  • ⁇ two-line gamma
  • niobium causes, for the same ratio content (Nb + 2 Ti), to decrease the total titanium percentage of the alloy.
  • Studies of the present invention have shown that such a decrease is also beneficial for improving oxidation resistance at elevated temperatures - a property also essential in high temperature working valves.
  • the ratio (Nb + 2 Ti) must therefore have a minimum content of 2.0% niobium, preferably niobium above 3.5%. being the ideal niobium content equal to or greater than 3.7%.
  • the content of these elements cannot be excessively high as it would promote the formation of coarse intermetals, impairing the mechanical properties. of the alloy in terms of mechanical strength and ductility, and raise the cost of the alloy.
  • the ratio value (Nb + 2 Ti) should be below 15.0%, preferably below 13.0%.
  • Carbon is added with the intention of combining with titanium and niobium to form hard carbide particles and impart abrasion resistance.
  • the carbon content must be at least 0.05%, preferably above 0.1%.
  • the percentage of hard particles must be below 5% by volume so as not to deteriorate the toughness and hot workability properties, the latter essential for hot forged valves.
  • the volume of these particles is determined by carbon since, in the formation of NbC or TiC, the alloy has excess Ti and Nb.
  • the carbon content is used as a controller of the particle volume formed, being below 1.0%, preferably below 0.40%.
  • Aluminum is very important for gamma phase ( ⁇ ') precipitation, and therefore for high temperature resistance. Another extremely important function of aluminum in the alloy is to increase oxidation resistance at high temperatures by increasing the formation of Al 2 O 3 during heating. However, aluminum contents should be restricted as very high amounts of this element may lead to deterioration of resistance at high temperatures and hot workability due to the formation of nitrides and phases such as ⁇ and ⁇ during long heating times.
  • the aluminum content therefore, should be between 0.5% and 4.0%, preferably between 1.0% and 3.0%, typically 2.0%.
  • Residuals Other elements, such as manganese, tungsten, molybdenum, copper, sulfur, phosphorus and those normally obtained as normal residues from the steelmaking process or liquid nickel alloys, should be understood as impurities related to the steelmaking deoxidation processes. or inherent in manufacturing processes. Therefore, the content of manganese, copper, tungsten and molybdenum at 5.0%, preferably below 2.0%, due to the destabilization of the relationship between the austenite and ferrite phases, as well as possible effects on the intermetallic phases present in the alloy. Phosphorus and sulfur segregate into grain boundaries and other interfaces and should therefore be below 0.20%, preferably below 0.05%, preferably maximum 0.005%.
  • the alloy as described may be produced by conventional or special processes such as melting in electric or vacuum furnaces, whether or not followed by remelting processes. Casting can be done in ingots by conventional casting or continuous casting, or even by other manufacturing processes involving liquid metal disaggregation and further aggregation, such as powder metallurgy and the spray forming or continuous casting process.
  • the end products can be obtained after hot or cold forming, end products being produced in the form of wire rod, blocks, bars, wires, plates, strips, or even can be products in the raw state of solidification.
  • Figure 1 shows the microstructure, observed under optical microscope, of alloys ET1 and PH to PI9, after polishing and attack with glyceregia reagent for 15 seconds. 120x magnification.
  • Figure 2 presents the result of computational image analysis to quantify the carbides observed in the alloys studied with different Ti, Nb and Al contents.
  • the analysis was performed in a total area of (65990,417) ⁇ 2 of the sample, in 50 random fields with 500x magnification.
  • Figure 3 shows the results of the alloy creep test of the present invention compared to the ET1 and ET2 alloys, evaluating the creep failure time at 800 ° C temperature and three stress levels.
  • Figure 4 compares the heat resistance of the alloys of the present invention to ET1 and ET2 alloys from the yield stress for various temperatures.
  • Figures 5 and 6 show the result of the abrasive wear test performed on alloys ET1, ET2 and alloys PM to PI7.
  • the test was performed with the sanding of pins (pin against sandpaper), the pins were made in the alloys after heat treatment of aging and the sanding with abrasives of alumina and grain # 120.
  • the average contact speed between the sandpaper and the pins was 100 m / min
  • EXAMPLE To define the alloy compositions of the present invention, various alloys were produced and compared to those of the prior art. Chemical compositions are shown in Table 1, hereinafter referred to as PI the alloys of the present invention and ET the alloys of the prior art; ET1 alloy corresponds to H1 461, ET2 to Inconel 751, and ET3 alloy to NCF 3015 (US 5,660,938). Relationships are also quantified: (Nb + 2 Ti); (Nb / C) and (Ti / Al) in Table 1.
  • Table 1 shows the significant reduction of the nickel content of the alloy in the compositions of the present invention in relation to the ET2 alloy, generating significantly lower cost.
  • ET2 and ET3 alloys also do not have significant carbon content, which does not promote carbide formation and the high wear resistance observed in other alloys.
  • Table 1 also shows the addition of different niobium contents in the alloys of the present invention, unlike the state of the art alloy (ET1), which has only titanium.
  • Relationship analysis (Nb + 2 Ti) is also interesting because it normalizes the atomic mass difference and thus relates to the atomic content. This is approximately constant between those of the present invention (PM to PI6) and the ET1 alloy; thus Ti atoms in the alloys of the present invention are gradually replaced by niobium until in the alloy PI4 titanium is completely replaced by niobium.
  • titanium and niobium show different effects on the studied alloys, so the substitution employed was very beneficial to the final properties, as described below. In this sense, it is very interesting to quantify and differentiate the alloys under study through the content of non-combined carbide niobium. This quantification can be assessed by the ratio (Nb / C).
  • Ti / Al The differences between titanium and aluminum contents between the different alloys can be assessed by the ratio (Ti / Al), which is very important for the properties of hot oxidation resistance and conformability of the alloys. This ratio (Ti / Al) is also shown in Table 1.
  • Ingot melting was performed in a close procedure for the ten alloys (ET1, ET2, ET3, PM, PI2, PI3, PI4, PI5, PI6, PI7) in a vacuum induction furnace, and casting was done in iron ingot molds. cast, producing a 55kg ingot. After solidification, the ingots were forged and rolled into 18 mm diameter round gauges. After solubilization, the bars were observed under an optical microscope, the result being shown in Figure 1. In the images it can be observed the increase of the carbides size with the substitution of the titanium for the niobium, fact confirmed by the quantitative analysis of the images presented in the Figure 2.
  • Table 1 Chemical compositions of three state of the art alloys (ET1, ET2 and ET3 ) and the alloys of the present invention (PI1 to PI7). Percentage by mass and balance in 1 iron.
  • Table 2 presents the hardness of ET1, ET2, ET3, PM,
  • Table 2 Response to heat treatment of state of the art alloys (ET1, ET2 and ET3) and alloys of the present invention (PM, PI2, PI3, PI4, PI5, PI6 and PI7). Hardness results in HB after solubilization at 1050 ° C and aging at
  • the alloys of the present invention are significantly more creep-resistant than ET alloy, being in alloys PI2, PI3, PI5 and PI6 equivalent or better than ET2 alloy (Inconel 751), although have considerably lower nickel content than this alloy.
  • the same behavior is observed, being alloys PI2, PI3, PI5 and mainly PI6 more resistant than alloy ET1 and ET2.
  • the PI4 alloy due to the higher concentration of coarse phases, has a reduction in hot strength and creep.
  • the alloys of the present invention were also superior to ET1 and ET2 alloys, as shown in Table 3; It is observed that the lower the titanium content, the higher the oxidation resistance of the alloy, the better the resistance observed for PI4 alloy without titanium. This is due to the effect of titanium on destabilizing the oxide layer formed on the surface of nickel-iron alloys and thus decreasing oxidation resistance. Another interesting effect to note is that among the low titanium alloys (PI2, PI3, PI4, PI5, PI6 and PI7), those with higher aluminum content (PI5, PI6 and PI7) have resistance to hot oxidation. higher under the test conditions. The assay was performed so that all samples of all alloys involved had identical dimensions, so as to have identical contact surface.
  • Table 3 Mass gain (in mg / cm 2 ) after 100, 200 and 400 hours at 800 ° C in atmosphere (air). The lower the mass gain, the greater the resistance to oxidation of the material.
  • the abrasive wear resistance follows the same trend of oxidation resistance, but for different reasons.
  • ET1 and PI1 to PI9 alloys have significantly higher wear resistance than ET2 alloy due to the presence of hard particles in their microstructures (as shown in Figure 1).
  • the higher the niobium content the lower the wear rate and therefore the higher abrasive wear resistance; This is due to the larger size of the carbides present in the microstructure of the highest niobium alloys, as shown in Figure 1 and quantified in Figure 2.
  • the industrial application of these alloys involves an aging heat treatment step after final part forming.
  • the alloys of the present invention find it easier to obtain the minimum hardness required in the application (about 330 HB - Brinell hardness scale), ie hardness above 330 HB is observed after only 20 minutes of treatment at 750 ° C. ° C, the hardness being always higher for the alloys of the present invention (PI5, PI6) than prior art alloys for the same treatment time, as can be seen in Figure 7.
  • Alloys PI5 and PI6 also exhibit better response to aging heat treatment at 690 ° C than the state of the art ET3 alloy, obtaining hardness above the minimum value required for application after one hour of treatment. This can be seen in Figure 8.
  • the reduction in aging treatment temperature and time is of vital importance for cost savings and productivity gains in material processing.
  • the alloys of the present invention in addition to the economic advantage of working with lower nickel content, also have better properties.
  • the alloys of the present invention have superior levels of high temperature properties and wear resistance, thus being important improvements for industrial application in combustion engine valves or even other components employed at high temperature and corrosive environments.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture Of Alloys Or Alloy Compounds (AREA)

Abstract

L'invention concerne des alliages de faible coût résistant aux sollicitations mécaniques associées à de hautes températures, résistant à la corrosion, résistant à l'abrasion, présentant une haute aptitude au formage, et répondant aux diverses sollicitations inhérentes aux conditions d'utilisation dans une soupape d'échappement ou d'admission pour moteurs à combustion interne. Ces alliages présentent, comme caractéristiques principales, la précipitation de Ni3Nb et de carbures de niobium dans leur microstructure, laquelle comprend, en pourcentage en masse: entre 0,15 et 0,50% de C, jusqu'à 3,0% de Mn, jusqu'à 1% de Si, entre 12,0 et 25,0% de Cr, entre 25,0 et 49,0% de Ni, jusqu'à 0,50% de Mo, jusqu'à 0,50% de W, jusqu'à 0,50% de V, entre 0,50 et 5,0% de Cu, entre 1,85 et 3,0% d'Al, entre 1,0 et 4,5% de Ti, entre 3,1 et 8,0% de Nb, entre 0,001 et 0,02% de B, entre 0,001 et 0,10% de Zr et jusqu'à 2,0% de Co, à condition que (Ni + Co) ne dépasse pas 50,0% en masse et ne soit pas inférieur à 25% en masse, le reste se composant de fer et des impuretés inévitablement présentes dans le procédé de fabrication de l'alliage.
PCT/BR2009/000293 2009-09-09 2009-09-09 Superalliage à base de nickel pour soupape de moteurs à combustion interne Ceased WO2011029164A1 (fr)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110465667A (zh) * 2019-09-25 2019-11-19 广西科技大学 一种涡轮增压器叶片及其制备方法
US11525172B1 (en) 2021-12-01 2022-12-13 L.E. Jones Company Nickel-niobium intermetallic alloy useful for valve seat inserts

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5660938A (en) * 1993-08-19 1997-08-26 Hitachi Metals, Ltd., Fe-Ni-Cr-base superalloy, engine valve and knitted mesh supporter for exhaust gas catalyzer
US20080008617A1 (en) * 2006-07-07 2008-01-10 Sawford Maria K Wear resistant high temperature alloy
US20090081074A1 (en) * 2007-06-07 2009-03-26 Celso Antonio Barbosa Wear resistant alloy for high temprature applications

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5660938A (en) * 1993-08-19 1997-08-26 Hitachi Metals, Ltd., Fe-Ni-Cr-base superalloy, engine valve and knitted mesh supporter for exhaust gas catalyzer
US20080008617A1 (en) * 2006-07-07 2008-01-10 Sawford Maria K Wear resistant high temperature alloy
US20090081074A1 (en) * 2007-06-07 2009-03-26 Celso Antonio Barbosa Wear resistant alloy for high temprature applications

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110465667A (zh) * 2019-09-25 2019-11-19 广西科技大学 一种涡轮增压器叶片及其制备方法
CN110465667B (zh) * 2019-09-25 2022-04-22 广西科技大学 一种涡轮增压器叶片及其制备方法
US11525172B1 (en) 2021-12-01 2022-12-13 L.E. Jones Company Nickel-niobium intermetallic alloy useful for valve seat inserts

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