NICKEL BASED ALLOY USEFUL FOR VALVE SEAT INSERTS

Description

FIELD OF THE INVENTION

[0001] The invention relates to nickel based alloys having high hardness and compressive yield strength. Such alloys are especially useful for engine parts such as valve seat inserts.

DESCRIPTION OF THE RELATED ART

[0002] Nickel based valve seat insert alloys generally have wear resistance, heat resistance, and corrosion resistance superior to those of high alloy steels, and are therefore often used as materials for structural members serving under severe conditions, such as valve seat inserts. Known nickel based alloys used for exhaust valve seat inserts, such as an alloy identified as J96 and marketed by L. E. Jones Company, have relatively good characteristics, including good hardness and compressive yield strengths. Another alloy marketed by L. E. Jones is J89, details of which are provided in U.S. Patent No. 6,482,275. In general, the J89 alloy includes, in weight percent (as used herein "percent" and "%" refer to percent by weight unless otherwise indicated), 2.25 to 2.6 % C, up to 0.5 % Mn, up to 0.6 % Si, 34.5 to 36.5 % Cr, 4.00 to 4.95 % Mo, 14.5 to 15.5 % W, 5.25 to 6.25 % Fe, balance Ni plus incidental impurities.

SUMMARY

[0003] Disclosed herein is a nickel based alloy comprising, in weight percentage: carbon from 0.5 to 1.5; chromium from 25 to 35; tungsten from 12 to 18; iron from 3.5 to 8.5; molybdenum from 1 to 8; manganese up to 0.50; silicon up to 1.0; up to a total of 1.5% Co, vanadium, titanium, niobium, hafnium, zirconium, tantalum, rare earth, yttrium, copper, sulphur, phosphorous, nitrogen and the balance nickel and incidental impurities. The alloy is suitable for valve seat insert applications in internal combustion engines.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0004] 

FIG. 1 is an OLM photomicrograph at 500X of J91 in an as-cast condition.

FIG. 2 is an SEM photomicrograph at 500X of J91 in an as-cast condition.

FIG. 3 is a graph of wear at elevated temperature for J3, J130, J160 and J91 alloys.

DETAILED DESCRIPTION

[0005] The nickel based alloy described herein (referred to as "the J91 alloy") has been designated to promote machinability while maintaining desired hardness and wear resistance at elevated temperatures. Through adjustments in carbon, chromium, nickel and tungsten contents, it is possible to provide a matrix material which is free of coarse primary carbides yet exhibits desired wear resistance properties. The microstructure of the J91 alloy can be characterized as spheroidal or egg-shaped eutectic domains interspersed with a Ni-rich FCC phase and thus provide desired wear resistance properties without reliance on coarse primary carbides.

[0006] In addition to improved machinability and desired hardness, the J91 alloy can exhibit high compressive yield strength, good corrosion resistance and good oxidation resistance.

[0007] Before embodiments are explained in detail, it is to be understood that the J91 alloy is not limited in its application to the details of the composition and concentrations of components set forth in the following description. The J91 alloy is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

[0008] While the J91 alloy is designed particularly for use in internal combustion engine valve seat inserts, other applications are feasible. Compared to the J89 alloy, the J91 alloy is based on experimental findings that hardness and compressive yield strength of the nickel based alloys can be obtained by removal of coarse primary carbides and creating an evenly distributed face centered cubic (FCC) nickel-solid solution phase in eutectic reaction phases matrix in which additional strengthening solutes can be introduced.

[0009] Carbon (C) is present in the J91 alloy in an amount ranging from 0.5 to 1.5 weight percent of the total alloy; preferably, about 0.95 to about 1.3 weight percent. The J91 alloy surprisingly exhibits wear resistance properties equivalent to that of the J89 alloy but with a much lower carbon content. Whereas the J89 alloy relies on the presence of coarse primary carbides to achieve wear resistance, the J91 alloy which is preferably free of coarse primary carbides can achieve desired wear resistance in an as-cast condition through an improved wear resistant matrix microstructures. By selection of Ni, Cr and W contents it is possible to increase the amount of eutectic structure through ternary eutectic reactions which produce spheroidal or egg-shaped eutectic domains interspersed with a Ni-rich FCC phase.

[0010] Chromium (Cr) is present in the alloy in an amount ranging from 25 to 35 weight percent of the total alloy, preferably 27 to 33 weight percent, and more preferably 28.5 to 31.5 weight percent of the total alloy. The chromium content can be selected such that the relative amounts of Cr, Ni and W move the J91 alloy closer to the center of the eutectic center point of the Ni-W-Cr ternary phase diagram so as to promote the tendency for intermetallic phase(s) formation between W and Ni. By increasing the amount of uniformly distributed eutectic structures, the matrix material can be made very wear resistant.

[0011] Tungsten (W) is present in the alloy in an amount ranging from 12 to 18 weight percent of the total alloy. Preferably, the tungsten content is at least 14 weight percent and at most 16 weight percent. A more preferred W content is about 14.5 to about 15.5 %.

[0012] Iron (Fe) is present in the alloy in an amount ranging from 3.5 to 8.5 weight percent of the total alloy; preferably, at least 5 weight percent and at most 7 weight percent. A preferred Fe content is 5.25 % to about 8.25%.

[0013] Molybdenum (Mo) is present in the alloy in an amount ranging from 1 to 8 weight percent of the total alloy. Generally, greater molybdenum increases alloy hardness and decreases carbide size; however, too much molybdenum may result in a brittle product. The weight percent molybdenum is preferably at least 2 weight percent and at most 6.25 weight percent. More preferably, the alloy contains about 4 to 5 weight percent Mo, most preferably the Mo content is 4.35 % to 4.95 %.

[0014] Manganese (Mn) can be added or present in an amount of up to about 0.5 weight percent of the total alloy. A preferred Mn content is about 0.25 % to about 0.5 %.

[0015] Silicon (Si) may be added to or present in the alloy at levels up to 1.0 weight percent of the total alloy. A preferred Si content is 0.15 % to 0.60 %.

[0016] The alloy may contain other intentionally added elements up to a total of 1.5 weight percent. These elements are cobalt (Co), vanadium (V), titanium (Ti), niobium (Nb), hafnium (Hf), zirconium (Zr), tantalum (Ta), rare earth, yttria (Y), copper (Cu), sulfur (S), phosphorus (P), nitrogen (N) or other elements. For example, the alloy may include up to 0.5% V, up to 0.5% Co, up to 0.03% P, up to 0.03% S.

[0017] The balance of the alloy is nickel (Ni) and incidental impurities. Generally, the alloy contains at least 30 weight percent nickel. A preferred Ni content is 35 to 45 %. Thus, the alloy preferably consists essentially of C, Cr, W, Mo, Fe, Ni, Mn and Si. As used herein "consisting essentially of' excludes additions which adversely affect machinability and wear properties of the alloy.

[0018] At 800°C., the matrix material between the carbides preferably contains a three-phase eutectic composition of the elements Cr--Ni--W, which provides increased strength. The relative concentration of Cr--Ni--W necessary to form a three-phase eutectic composition may be determined by reference to a Cr--Ni--W ternary component phase diagram. Such phase diagrams are shown, for example, on page 3-48 of the ASM Handbook, Copyright 1992, Volume 3, which is herein incorporated by reference.

[0019] In a highly preferred embodiment, the alloy comprises:

Element	Weight Percent Range
C	0.95-1.3
Cr	28.5-31.5
Mo	4.35-4.95
W	14.5-15.5
Fe	5.25-8.25
Si	0.15-0.6
Mn	0.25-0.50
V	up to 0.5
Co	up to 0.5
S	up to 0.03
P	up to 0.03
Ni	balance
other elements	up to 1.5

[0020] Metal parts can be made from the alloy by casting or forming from a powder and sintering, or the alloy can be used as a coating to hardface parts. Preferably, the alloy is manufactured by casting. Casting is a conventional process in which raw materials are added together and melted to liquid state, and then poured into a cast mold.

[0021] Preferably, the metal parts are valve seat inserts made by casting or powder metallurgy for use in internal combustion engines.

[0022] Although the J91 alloy is nickel-based, the thermal expansion coefficient of the alloy tends to be closer to that of iron than nickel. (The thermal expansion coefficient of cast iron is approximately 11.5 x 10^-6 mm/mm °C. at a temperature of 25-600°C.) This is beneficial because the valve seat insert tends to be much hotter than the surrounding material when the engine is operating. If the thermal expansion coefficient of the valve insert alloy closely matches that of the cylinder head alloy, this enables the insert and cylinder head to expand at the same rate, thereby improving insert retention characteristics.

[0023] The J91 alloy has good high temperature compressive yield strength which increases wear resistance and decreases material yielding during operation. Decreased yielding serves to improve insert retention. Preferably, the alloy has a compressive yield strength of at least about 110 thousand pounds per square inch (KSI) at room temperature; more preferably, at least about 130 KSI at room temperature.

[0024] Increased hot hardness contributes to improved wear resistance and provides a safety factor for inserts which run beyond the normal operating temperature.

EXAMPLE

[0025] Comparative properties of the J91 and J89 alloys are set forth in the following tables and discussion.

Typical Microstructures

[0026] The J91 alloy possesses a matrix composed of eutectic reaction phases along with a small amount of randomly distributed FCC nickel solid solution phase. The nickel solid solution phase is distributed along the grain boundaries of eutectic phases. An optical light microscope (OLM) photomicrograph and a scanning electron microscope (SEM) photomicrograph exhibiting typical J91 microstructures are depictured in Figures 1 and 2, respectively. A heat of J89 (Heat No. 7K17K) and a heat of J91 (Heat No. 8L15XA) were employed for the optical light microscopic microstructural characterization. In addition, a heat of J91 (Heat No. 7G10XA) and a heat of J89 (7K17K) were employed for the scanning electron microscopic microstructural characterization. The composition of above three heats involved is summarized in the Table 1.

Table 1. Composition of J89 and J91 heats applied for the microstructural characterization.

Alloy/Heat No.	C	Si	Mn	Cr	Mo	W	Fe	Ni
J89/7K17K	2.25	0.20	0.39	35.12	4.48	15.00	5.69	36.49
J91/8L15XA	1.19	0.20	0.52	30.51	4.44	14.92	7.19	40.72
J91/7G10XA	1.21	0.16	0.02	30.54	4.88	14.20	4.47	41.32

Samples Used for Hot Hardness Measurement

[0027] Composition of the heats used for making hot hardness measurement samples for alloys J89 and J91 are summarized in Table 2.

Table 2. Composition of alloy / heat numbers of J89 and J91 used for the hot hardness tests.

Alloy/Heat No.	C	Si	Mn	Cr	Mo	W	Fe	Ni
J89/4E18D	2.40	0.39	0.26	34.92	4.38	14.90	5.93	36.64
J91/8D02Q	0.98	0.46	0.22	30.55	4.36	15.25	6.95	41.06

Material Properties

[0028] Typical bulk hardness of alloy J91 is Rockwell C (HRC) of 48 to 52, preferably about 49 to 51. Thus, alloy J91 possesses a bulk hardness in between that for J96 (HRC 40) and J89 (HRC 55).

[0029] A comparison of hot hardness (in Vickers HV10 units) for J89, J91, and J96 (for alloys summarized in Table 2) is summarized in Table 3. J91 was found to possess a significant greater hot hardness compared to J96, even though J91 does not contain coarse primary carbide in its microstructures.

Table 3. A comparison of hot hardness among alloys J89, J91, and J96.

Temperature (°F)	J89 (HV10)	J91 (HV10)	J96 (HV10)
75	611	456	367
200	641	426	360
400	555	387	325
600	602	375	337
800	532	372	322
1000	556	366	338
1200	504	349	292
1400	463	318	250
1600	320	220	153

Samples Used for Compression Yield Strength Test

[0030] The J89 and J91 samples used for compression tests are set forth in Table 4.

Table 4

Alloy	C	Si	Mn	Cr	Mo	Fe	W	Ni
J89	2.51	0.56	0.48	36.47	4.15	6.7	15.44	33.69
J91	1.33	0.24	0.1	30.29	4.81	8.69	14.15	40.39

[0031] A comparison of compressive yield strength of J89, J91, and J96 is shown in Table 5. It is clearly shown that J91 possesses compressive yield strengths for the applied temperature range between that for alloys J89 and J96.

Table 5. Comparison of compressive yield strength (KSI) among J89, J91, and J96.

Temperature (°F)	J89 (KSI)	J91 (KSI)	J96 (KSI)
75	130.0	113.2	65.1
600	115.4	88.4	61.5
800	112.2	83.7	64.0
1000	115.4	93.1	66.5

Samples Used for Linear Thermal Expansion Coefficient Measurement

[0032] A heat of J89 (4E18D) and a heat of J91 (7G10XA) were used for carrying out the thermal expansion coefficient measurement. Compositions for the two involved heats are summarized in Table 6.

Table 6. Composition of J89 and J91 heats applied for thermal expansion coefficient test.

Alloy/Heat No.	C	Si	Mn	Cr	Mo	W	Fe	Ni
J89/4E18D	2.40	0.39	0.26	34.92	4.38	14.90	5.93	36.64
J91/7G10XA	1.21	0.16	0.02	30.54	4.88	14.20	4.47	41.32

[0033] Results of the thermal coefficient measurement of alloys J89 and J91 with above described heats are summarized in Table 7.

Table 7. Thermal expansion coefficient (x10^-6 mm/mm °C) for alloys J89 and J91

Alloy/Heat No.	25-200°C	25-300°C	25-400°C	25-500°	25-600°C
J89/4E18D	10.32	11.07	11.55	11.95	12.38
J91/7G10XA	10.95	11.63	12.15	12.52	13.01

[0034] Practically, the thermal expansion coefficient of J91 was only slightly greater than that for J89. Such a low thermal expansion coefficient is favorable for heavy duty engine valve seat insert applications.

Wear Resistance

[0035] The wear resistance of alloy J91 under engine wear conditions is expected to be similar to J89. A comparison of wear resistance as a function of test temperature for J91, J3, J130, and J160 vs Pyromet 31 V valve material is exhibited in Figure 3 and Table 8, respectively.

[0036] It is clearly shown that in the exhaust temperature range, J91 exhibited overall the least total materials wear among the four materials pairs evaluated. Within the lower test temperature range (ambient to 250°C), J91 showed a similar wear resistance to alloys J130 and J160 when paired with Pyromet 31 V valve material.

Table 8. Summary of the Plint wear test results.

Total Materials Wear of J130, J160, J3 and J91 (pin) vs Pyromet 31 (plate)
Temp (°C)	J3	J130	J160	J91
20	1.0	3.9	5.3	4.7
200	2.9	5.1	4.7	5.5
250	5.0	4.9	5.5	3.0
300	3.6	3.4	3.3	3.7
350	5.7	3.3	4.2	2.9
400	4.6	3.1	3.7	2.1
450	5.2	1.9	4.3	1.6
500	1.9	0.8	1.6	2.2

Claims

1. A nickel based alloy consisting of, in weight percentage: carbon from 0.5 to 1.5; chromium from 25 to 35; tungsten from 12 to 18; iron from 3.5 to 8.5; molybdenum from 1 to 8; manganese up to about 0.50; silicon up to about 1.0; up to a total of 1.5 cobalt, vanadium, titanium, niobium, hafnium, zirconium, tantalum, rare earth, yttrium, copper, sulfur, phosphorus or nitrogen; and the balance nickel from 30 to 45 and incidental impurities.

2. The alloy of Claim 1, wherein the alloy comprises 0.95 to 1.30 weight percent carbon.

3. The alloy of Claim 1, wherein the alloy comprises 28.5 to 30.5 weight percent chromium.

4. The alloy of Claim 1, wherein the alloy comprises at least 14.0 weight percent tungsten.

5. The alloy of Claim 1, wherein the alloy comprises at least 5.0 weight percent iron and at most 7.0 weight percent iron.

6. The alloy of Claim 1, wherein the alloy comprises 4.35 to 4.95 weight percent molybdenum.

7. The alloy of Claim 1, wherein the alloy comprises at most 1.3 weight percent carbon or wherein the alloy comprises at most 32.0 weight percent chromium or wherein the alloy comprises at most 16.0 weight percent tungsten.

8. The alloy of Claim 1, wherein the alloy comprises 40 to 42 weight percent nickel or wherein the relative concentration of Cr, Ni and W is such that a three-phase eutectic composition forms at a temperature of about 800°C.

9. The alloy of Claim 1, wherein the alloy consists essentially of, in weight percentage: carbon from 0.95 to 1.3; chromium from 28.5 to 31.5; tungsten from 14.5 to 15.5; iron from 5.25 to 8.25; molybdenum from 4.35 to 4.95; manganese from 0.25 to 0.5; silicon from 0.15 to 0.6; vanadium up to about 0.5; cobalt up to about 0.5; sulfur up to about 0.03; phosphorus up to about 0.03; nickel from 38 to 42; and incidental impurities.

10. The alloy of Claim 1 or Claim 9, wherein said alloy is a casting.

11. The alloy of Claim 1, wherein said alloy is a valve seat insert for an internal combustion engine or wherein the alloy has an as-cast microstructure comprising a wear resistant matrix of spheroidal eutectic domains free of coarse primary carbides.

12. A valve seat insert for use in an internal combustion engine, said valve seat insert being made of the alloy of claim 1.

13. The valve seat insert of Claim 12, wherein the valve seat insert is a casting.

14. The valve seat insert of Claim 12, wherein the alloy consists of, in weight percent: carbon from 0.95 to 1.3; chromium from 28.5 to 31.5; tungsten from 14.5 to 15.5; iron from 5.25 to 8.25; molybdenum from 4.35 to 4.95; manganese from 0.25 to 0.5; silicon from 0.15 to 0.6; total of vanadium and cobalt not exceeding 0.5; sulfur not exceeding 0.03; phosphorus not exceeding 0.03; and the balance nickel and incidental impurities.

15. The valve seat insert of Claim 12, having a hardness of 48 to 52 Rockwell C.

Ansprüche

1. Eine Legierung auf Nickelbasis, bestehend aus, in Gewichtsprozent: 0,5 bis 1,5 Kohlenstoff, 25 bis 35 Chrom, 12 bis 18 Wolfram, 3,5 bis 8,5 Eisen, 1 bis 8 Molybdän, bis zu etwa 0,50 Mangan, bis zu etwa 1,0 Silicium, insgesamt bis zu 1,5 Cobalt, Vanadium, Titan, Niob, Hafnium, Zirconium, Tantal, Seltenerden, Yttrium, Kupfer, Schwefel, Phosphor oder Stickstoff, und als Rest 30 bis 45 Nickel und zufällige Verunreinigungen.

2. Die Legierung nach Anspruch 1, wobei die Legierung 0,95 bis 1,30 Gew.-% Kohlenstoff umfasst.

3. Die Legierung nach Anspruch 1, wobei die Legierung 28,5 bis 30,5 Gew.-% Chrom umfasst.

4. Die Legierung nach Anspruch 1, wobei die Legierung wenigstens 14,0 Gew.-% Wolfram umfasst.

5. Die Legierung nach Anspruch 1, wobei die Legierung wenigstens 5,0 Gew.-% Eisen und höchstens 7,0 Gew.-% Eisen umfasst.

6. Die Legierung nach Anspruch 1, wobei die Legierung 4,35 bis 4,95 Gew.-% Molybdän umfasst.

7. Die Legierung nach Anspruch 1, wobei die Legierung höchstens 1,3 Gew.-% Kohlenstoff umfasst, oder wobei die Legierung höchstens 32,0 Gew.-% Chrom umfasst, oder wobei die Legierung höchstens 16,0 Gew.-% Wolfram umfasst.

8. Die Legierung nach Anspruch 1, wobei die Legierung 40 bis 42 Gew.-% Nickel umfasst, oder wobei die relative Konzentration von Cr, Ni und W derart ist, dass sich bei einer Temperatur von etwa 800°C eine dreiphasige eutektische Zusammensetzung bildet.

9. Die Legierung nach Anspruch 1, wobei die Legierung im Wesentlichen besteht aus, in Gewichtsprozent: 0,95 bis 1,3 Kohlenstoff, 28,5 bis 31,5 Chrom, 14,5 bis 15,5 Wolfram, 5,25 bis 8,25 Eisen, 4,35 bis 4,95 Molybdän, 0,25 bis 0,5 Mangan, 0,15 bis 0,6 Silicium, bis zu etwa 0,5 Vanadium, bis zu etwa 0,5 Cobalt, bis zu etwa 0,03 Schwefel, bis zu etwa 0,03 Phosphor, 38 bis 42 Nickel, und zufällige Verunreinigungen.

10. Die Legierung nach Anspruch 1 oder Anspruch 9, wobei die Legierung ein Guss ist.

11. Die Legierung nach Anspruch 1, wobei die Legierung ein Ventilsitzring für einen Verbrennungsmotor ist, oder wobei die Legierung eine Mikrostruktur im Gusszustand besitzt, die eine verschleißfeste Matrix aus sphäroidischen eutektischen Domänen, frei von groben primären Carbiden, umfasst.

12. Ein Ventilsitzring zur Verwendung in einem Verbrennungsmotor, wobei der Ventilsitzring aus der Legierung nach Anspruch 1 hergestellt ist.

13. Der Ventilsitzring nach Anspruch 12, wobei der Ventilsitzring ein Guss ist.

14. Der Ventilsitzring nach Anspruch 12, wobei die Legierung besteht aus, in Gewichtsprozent: 0,95 bis 1,3 Kohlenstoff, 28,5 bis 31,5 Chrom, 14,5 bis 15,5 Wolfram, 5,25 bis 8,25 Eisen, 4,35 bis 4,95 Molybdän, 0,25 bis 0,5 Mangan, 0,15 bis 0,6 Silicium, insgesamt nicht mehr als 0,5 Vanadium und Cobalt, nicht mehr als 0,03 Schwefel, nicht mehr als 0,03 Phosphor, und als Rest Nickel und zufällige Verunreinigungen.

15. Der Ventilsitzring nach Anspruch 12, der eine Rockwell-C-Härte von 48 bis 52 besitzt.

Revendications

1. Alliage à base de nickel constitué par, en pourcentage en poids : de 0,5 à 1,5 de carbone ; de 25 à 35 de chrome ; de 12 à 18 de tungstène ; de 3,5 à 8,5 de fer ; de 1 à 8 de molybdène ; jusqu'à environ 0,50 de manganèse ; jusqu'à environ 1,0 de silicium ; jusqu'à 1,5 en tout de cobalt, vanadium, titane, niobium, hafnium, zirconium, tantale, terre rare, yttrium, cuivre, soufre, phosphore ou azote ; le reste étant de 30 à 45 de nickel et des impuretés inévitables.

2. Alliage selon la revendication 1, l'alliage comprenant de 0,95 à 1,30 en pourcentage en poids de carbone.

3. Alliage selon la revendication 1, l'alliage comprenant de 28,5 à 30,5 en pourcentage en poids de chrome.

4. Alliage selon la revendication 1, l'alliage comprenant au moins 14,0 en pourcentage en poids de tungstène.

5. Alliage selon la revendication 1, l'alliage comprenant au moins 5,0 en pourcentage en poids de fer et au plus 7,0 en pourcentage en poids de fer.

6. Alliage selon la revendication 1, l'alliage comprenant de 4,35 à 4,95 en pourcentage en poids de molybdène.

7. Alliage selon la revendication 1, l'alliage comprenant au plus 1,3 en pourcentage en poids de carbone ou l'alliage comprenant au plus 32,0 en pourcentage en poids de chrome ou l'alliage comprenant au plus 16,0 en pourcentage en poids de tungstène.

8. Alliage selon la revendication 1, l'alliage comprenant de 40 à 42 en pourcentage en poids de nickel ou dans lequel la concentration relative de Cr, Ni et W est telle qu'une composition eutectique de trois phases se forme à une température d'environ 800 °C.

9. Alliage selon la revendication 1, l'alliage constitué essentiellement, en pourcentage en poids, par le suivant : de 0,95 à 1,3 de carbone ; de 28,5 à 31,5 de chrome; de 14,5 à 15,5 de tungstène ; de 5,25 à 8,25 de fer ; de 4,35 à 4,95 de molybdène ; de 0,25 à 0,5 de manganèse ; de 0,15 à 0,6 de silicium ; jusqu'à environ 0,5 de vanadium ; jusqu'à environ 0,5 de cobalt ; jusqu'à environ 0,03 de soufre ; jusqu'à environ 0,03 de phosphore ; de 38 à 42 de nickel ; et des impuretés inévitables.

10. Alliage selon la revendication 1 ou la revendication 9, l'alliage étant une pièce coulée.

11. Alliage selon la revendication 1, l'alliage étant un insert de siège de soupape pour un moteur à combustion interne ou l'alliage étant une microstructure brute de coulée comprenant une matrice résistant à l'usure de domaines eutectiques sphéroïdes dépourvue de carbures primaires grossiers.

12. Insert de siège de soupape destiné à être utilisé dans un moteur à combustion interne, ledit insert de siège de soupape étant réalisé dans l'alliage selon la revendication 1.

13. Insert de siège de soupape selon la revendication 12, l'insert de siège de soupape étant une pièce coulée.

14. Insert de siège de soupape selon la revendication 12, dans lequel l'alliage est constitué par, en pourcentage en poids : de 0,95 à 1,3 de carbone ; de 28,5 à 31,5 de chrome ; de 14,5 à 15,5 de tungstène ; de 5,25 à 8,25 de fer ; de 4,35 à 4,95 de molybdène ; de 0,25 à 0,5 de manganèse; de 0,15 à 0,6 de silicium; pas plus de 0,5 en tout de vanadium et de cobalt ; pas plus de 0,03 de soufre ; pas plus de 0,03 de phosphore ; le reste étant du nickel et des impuretés inévitables.

15. Insert de siège de soupape selon la revendication 12, ayant une dureté de 48 à 52 Rockwell C.

Drawing