NICKEL-RICH WEAR RESISTANT ALLOY AND METHOD OF MAKING
AND USE THEREOF
BACKGROUND
[0001| The invention relates to nickel-rich alloys having hardness and wear resistance properties suitable for use in engine parts such as valve seat inserts. [0002] Engine operating conditions in internal combustion engines such as diese! engines are placing ever increasing demands on materials used for valve seat inserts. As a result, there is a need for improved valve seat insert materials.
SUMMARY
[0003] According to a preferred embodiment, a nickel-rich wear resistant alloy comprises in weight % 0,5 to 2.5% C, 0.5 to 2 % Si, up to 1% Mn, 20 to 30% Cr, 5 to 15% Mo, 5 to 15% W, 15 to 30% Fe, balance Ni.
[0004| The alloy can include further alloying constituents such as up to 1.5% each of Ti, Al, Zr, Hf, Ta, V, Nb, Co and Cu, up io 0.5% B andJor up lo 0.5% Mg plus Y. [0005} The alloy preferably has a microstructure containing predominantly eutectic reaction phases, fine intermetallic phases and precipitation carbides. For instance, the microstructure may contain Cr. Ni, W rich intermetallic phases and/or the microstructure may contain uniform lamellar type eutectic solidification structures. The alloy is useful as a valve seat insert for internal combustion engines such as diesel engines.
[0006| For a valve seat insert containing up to 1.8%) C the microstructure preferably is free of primary dendritic carbides. For a valve seat insert alloy containing over 1.8% C the microstructure preferably contains non-dendritic type primary carbides. For a valve scat insert containing up to 1.5% C the microstructure preferably includes solid solution phases encompassed by eutectic reaction products. [0007| According to another embodiment, a valve seat insert comprises in weight % 0.5 to 2.5% C, 0.5 to 2 % Si, up to 1% Mn, 20 to 30% Cr, 5 to f 5% Mo, 5 to 15% Cr, 15 to 30% Fe, balance Ni. The valve seat can be manufactured by casting and have an as cast hardness of at least about 40 Rockwell C, a compressive yield strength at room temperature of 95 ksi, and/or ;i compressive yield strength al SOOT

of at least 85 ksi. Preferably, the valve seat insert exhibits a dimensional stability of less than about 0.5xlO'3 inches after 20 hours at 1200"F.
[0008] In another embodiment, a method of manufacturing an internal combustion engine such as a diesel engine comprises inserting the valve seat insert in a cylinder head of the engine. In operating an internal combustion engine such as a diesel engine, a valve is closed against the valve seat insert to close a cylinder of the engine and fuel is ignited in the cylinder to operate the engine.
BRJEF DESCRIPTION OF THE DRAWING FTGURES
(00091 FIGURE I ILLUSTRATES J96 EXHAUST INSERT AT SEAT LD.
(00101 Figure 2 illustrates correlation between measured and predicted bulk
hardness in J73 alloy system.
[0011} Figure 3 illustrates a secondary electron SEM morphology in J73 (4G281)
casting (2000X).
(0012] Figure 4 illustrates an EDS spectrum showing typical composition for
phase A in Figure 3.
DETAILED DESCRIPTION
[0013] A nickel-rich wear resistant alloy designed primarily for use in high temperature applications such as valve seat inserts and the like is disclosed herein. The alloy is a nickel rich multi-phase alloy metallurgicaHy designed to achieve intermetallic strengthening wiihin a euteetie reaction solidification substructure. Due to its unique strengthening mechanisms, the alloy has a relatively high compressive yield strength and toughness compared with commercially available nickel-based valve seat alloys, particularly at elevated temperature. The alloy also exhibits a relatively low thermal expansion coefficient which is an advantage for exhaust valve seat insert applications. The combination of high compressive strength at elevated temperature and low thermal expansion coefficient indicates that the alloy should have excellent insert retention capabilities for exhaust insert applications.
(0014) The alloy is preferably free of large primary carbides and coarse solidification substructures. The high temperature wear resistance and strength of

the alloy is preferably achieved by its hard intermetallic phases and finely distributed solidification substructure. The alloy preferably includes a high chromium content and is preferably free of conventional MC type carbide alloying elements, such as niobium and tantalum. Further, by combining carbon, silicon, and chromium in accordance with preferred embodiments of the alloy hardness, strength, and wear resistance can be substantially improved while providing very desirable micro structures for valve seat insert applications. An additional advantage of the alloy is that solid-state phase transformation reactions preferably do not occur within a temperature range from 25-1000°C, thus, the alloy does not require heat treatment to achieve high hardness, streiigth, and thermal dimensional stability for elevated temperature applications.
(0015} The alloy can exhibit improved wear performance when run against conventional nickel-based valve materials such as Inconel 751 and Nimonic 80A as well as cobalt-based valve facing materials known as Stellite 1. Excellent wear performance of Ihe alloy has been demonstrated in the Flint TE77 high temperature reciprocating wear test (ASTM Standard G133). The alloy outperforms other insert alloys such as cobalt-based J3 and nickel-based BX2 (representative of alloys in U.S. Patent 6,200,688) as tested against Inconel 751 in both the intake and exhaust temperature ranges. The alloy also outperformed BX2 in wear tests with Nimonic 80A. Further, the alloy outperforms both cohalt-based J3 and iron-based Jl 30 as tested against Stellite 1 within the exhaust temperature range. [0016] Due to its unique alloy design concept, the alloy is significantly differentiated from any current commercially available nickel-based alloy, particularly for valve seat insert applications.
[00171 Historically, numerous high temperature strengthening mechanisms have been applied to a nickel matrix to make nickel-based superalloys among the most widely utilized metallic materials for elevated temperature applications. Desired material properties of nickel-based alloys include elevated temperature fatigue strength, creep strength, hot hardness, corrosion resistance, and oxidation resistance. Primary concerns for valve seat insert materials, such as J96 and JI00 (ref. SAE Sfd. J1692), has been high insert outside diameter (O.D.) deformation and seat surface wear. Insert O.D. deformation leads to loss of interference fit potentially resulting in

catastrophic engine failure due to insert drop-out. Insert drop out is primarily an exhaust valve scat insert issue and is caused by a combination of high insert operating temperature, high thermal expansion coefficient relative to cast iron, and low compressive yield strength at elevated temperature. Seat surface wear of J96 and J100 is primarily caused by a combination of low matrix strength and the fracturing of large rod-like primary carbides which occurs as the matrix deforms (see Figure 1). In recent years, combustion pressure in diesel engines has been trending higher to meet goals of both engine performance and emissions reduction. This trend has been accompanied by an increased use of nickel-based valve materials, such as lnconel 751 and Nimonic 80A, to take advantage of their improved high temperature fatigue strength relative to iron-based valve materials. In some recent applications with nickel-based valves, higher wear rates of nickel-based insert materials have been observed. As such, there is an industry need for a new valve seat insert material which possesses higher strength and lower thermal expansion coefficient as well as a microstructure that improves wear performance compared to commercially available nickel-based valve seat inserts. To meet this; combination of objectives, improvements to matrix strength and reduction of carbide size was investigated in developing a nickel-rich alloy referred to herein as the J73 alloy. The J73 alloy was designed to meet this need as well as the continuing need for improved wear performance with iron or cobalt-based vaive or valve facing materials.
J0018J In a preferred embodiment, it is desired that the nickel-rich J73 alloy exhibits improvement in wear resistance and compressive strength for high performance engine applications which use nickel-based valve materials. According to a preferred embodiment, the nickel-rich wear resistant alloy comprises in weight % 0.5 to 2.5% C, 0.5 to 2 % Si, up to 1% Mn, 20 to 30% Cr, 5 to 15% Mo, 5 to 15% W, 15 to 30% Fe, balance Ni. m an embodiment, C is t .5 to 1.6%, Si is 1.0 to 1.1 %, Cr is 20 to 25% and Ni is 25 to 50%. Preferably, Fe exceeds Cr by 0.5% to 5%, Ni exceeds Fe by 5 to 15% and W exceeds Mo by up to 2%. The alloy is a multi-component based (Ni-Cr-Fe-W-Mo) alloy system containing predominantly eutectic reaction phases, fine intermetallic phases, and piecipitation carbides. Due to the nature of the eutectic reaction during the solidification process, the alloy can exhibit

relatively good castability demonstrated by the following discussion of nine experimental heats. The composition of these nine heats of the alloy along with the as-cast bulk hardness is tabulated in Table 1.
{0019] Table 1 - Summary of Nine Experimental Heats

Trial Heatfl C Mn Si Cr Mo W Co Fc Ni V HRc
1 3E28XA J.57 0.08 J. 00 22.4J £.66 10.56 0.48 2.3.15 31.94 IO0OT (KSI)
J89 130 115 1)2 US
J96 67 67 63 67
JIO0 63 60 57 62
J73 (3E28XA) 98 95 86 89
|0033| The J89, J96 and JW0 alloys referred to in Table 3 include the following alloy composilions: J89 has 2.440% C, 0.298% Mn, 0.525% Si, 34.73% Cr, 15.21% W, 4.580% Mo, 0.090% Fe, 0.050% Co, 35.93% Ni and 0.146% incidental impurities, J96 has 2,510% C, 0.253% Mn, 0.700% Si, 28.26% Cr, 15.34% W, 0.063% Mo, 6.050% Fe, 0.920% Co, 45.64% Ni and 0.264% incidental impurities, and J100 has 2.238% C, 0.338% Mn, 0.71 fi% Si, 27.61 % Cr, 15.41% W, 0.027% Mo, 5.540% Fe, 9.735% Co, 38.35% Ni and 0.034% incidental impurities.

(00341 It can be seen that two of the tested materials, J96 and J100, have significantly lower compressive strength than the J73 alloy, particularly at elevated temperature. This is one of the primary nickel-based material deficiencies that the J73 alloy sought to improve upon. The data show that the J73 alloy has provided a 30-40% improvement in compressive strength at elevated temperatures. J89 is a nickcl-bascd alloy intended to improve strength and wear resistance relative to .196 and J100; however, it utilizes a very different elemental approach than the J73 alloy. Though the strength increase of the J73 alloy relative to J96 and J100 is less than was achieved with J89, the major advantage of the J73 alloy relative to J'89 is improved machinability.
10035] One additional point of interest for the J73 alloy is the slight strengthening which occurs at 1000°F. This is also observable in alloys J89 and J96, but not J100. It is likely that a secondary precipitation strengthening takes place at 1000°F. in these alloys which is a desirable feature for nickel rich valve seat insert alloys to help protect against strength loss at extreme temperature. The secondary precipitation effect is somewhat more pronounced in J96 because it contains a significant amount of a free nickel solid solution phase (FCC). J0036] Six additional heats of the allny (Trials 10- 15") were made using H sixty-pound furnace to further explore the influence of carbon and silicon on the ^stability and bulk hardness of the alloy. One design criteria was to create a lower hardness version of the alloy with improved inicrostructura! characteristics. An advantage of lower insert hardness in certain valve train applications is that it will tend to minimize valve wear, possibly at the expense of increased insert wear; however, the combined wear would be less. As such, for wear problems where valve wear is a high percentage of the total wear, a softer version of the insert alloy would be desirable.
[0037| For trials 10-15, the iron content was about 20 wt. %and the nickel content was about 34 wt. %. One stack of insert castings was made with each of the six experimental heats. Trials 10-12 tested different carbon contents whereas Trials 13-15 tested different silicon contents at a 1.1% carbon target. Table 4 summarizes the composition and as-cast hardness results for these experimental heats.

(0038] Table 4. Summary of Six Additional Experimental Heal::

Trial Heat# C Mn Si Cr Mo W Co Fc Ni V HRc
10 4117XA 0.49 0.09 1.12 23.08 9.05 11.07 <0.1 21.13 33.75 O.l 34.3
11 4ECI7XA 0.78 0.07 1.06 24.12 9.02 10.72 O.I 20.(6 33.84 O.l 36.4
12 4K17XB 1.48 0.07 1.06 24.16 8.99 10.62 <0.1 19.91 33.48 O.I 49.8
13 4K18XA 1.09 0.06 0.80 24.30 9.13 10.68 <0.1 19.85 33.85 <0.1 42.6
14 4K18XB 1.08 0.07 1.52 23.95 9.16 10.60 <0.l 19.44 33.75 O.I 44.0
15 4K19XA 1.01 0.06 0.53 24.19 9.20 10.74 <0.1 19.92 34.11 O.l 40.5
i0039) Pouring temperature of all heats was between 2870-2920°F. All insert castings filled completely except for Trial ! 5 (T-Tf-qf 4KIQX A) which experienced incomplete fill in the top mold. The incomplete fill was primarily caused by (he significantly low silicon content of 0.53%., therefore, for cast parts, at least 0.5% silicon is believed to be desirable for improving castability. Further, a metallographic examination of heat4K19XA showed the existence of bulk shrinkage at the center of the insert cross-section though it was relatively small in size. Comments regarding these trials are as follows:
|00401 Trails 10 and 11 shows that at carbon levels of 0.5% and 0.8%, bulk hardness drops to the mid-30's Re even with target levels of silicon and chromium. This hardness is likely too iow to be useful tor cast valve seal insert applications. [0041] Trial 12 demonstrated high hardness again, this time with lower iron and higher nickel than present in the heats for Trials 1-9. There was also no vanadium or cobalt in this heat.

100421 Trials 13-15 show that with carbon content at about 1.1 vvl.%, hardness moved up to the low 40's Re. The combination of 1.1% carbon with high silicon of 1.5% (Trial 14) produced an increase in hardness to 44 Re; however, higher hardness is preferably achieved by reversing these percentages (i.e. 1.5% C, 1.1 % Si.) as demonstrated in Trial 12 which exhibited a hardness of about 50 Re. [0043] The overall results of Trials 10-15 confirm earlier Findings regarding a balance between carbon, silicon, and chromium to produce desired hardness. Silicon clearly plays a role in determining final hardness, but reaching the high 40's HRc is not possible with silicon alone. It appears that carbon and silicon contents must also be controlled to achieve the desired high hardness. Silicon is of lesser concern if a low 40's HRc version of the alloy is desired. Trial \2 represents a preferred combination of carbon, silicon, and chromium, approx. 1.5-1.6% C, 1.0-1.1% Si, and 23-25% Cr, to produce the highest hardness in this alloy system.
Relationship of Bulk. Hardness and Alloying Elements (0044) The elemental chemistry of all 15 experimental heats (Tables 2 & 4) of the alloy were used to carry out a multiple linear regression study to determine the relative mathematical strength of the various alloying elements on the bulk hardness. The results of the linear regression study is presented in Equation 1;
BulkHRc = -1.6 + 7.89C-0.71Si+1.49Cr + 9.97Co-3.l5V (1)
[0045] When studying the relative effects of the various elements on Bulk HRc, the relative effect of each element is the product of the coefficient and the elemental % content. As such, the primary drivers ofhardness effect in equation (1) are carbon and chromium. Though chromium has a lower positive coefficient, it's content is much higher making its overall contribution to the equation significant. [0046] Figure 2 shows the correlation between measured and calculated bulk hardness using Equation 1. A reasonable trend was achieved although only fifteen experimental heats were available for this study.

Thermal Kxpansion Coefficient
|0047] J73 Heat 3E28XA (Trial 1) was used for determining the thermal
expansion coefficient. A comparison of thermal expansion coefficient for materials including the J73 alloy, J89, J96, J100, J3, and J130 are summarized in Table 5. Cobalt-based J3 and iron-based J130 are included for comparative purposes. All the (hernial expansion coefficient tests were conducted using I inch long and 0.5 inch in diameter cylindrical specimens.

|0049] Table 5 shows that the J73 alloy possesses a relatively low thermal expansion coefficient compared with J96 and J100. The most desirable thermal expansion coefficient for heavy duty valve seat insert applications is one that matches the cylinder head cast iron, typically about 11.5 x 10"6mm/rnm°C, Cobalt-based alloys and nickel-based alloys often possess a relatively high thermal expansion coefficient and the relatively low thermal expansion coefficient of the J73 alloy is an advantage and is attributable to the alloy system design. (0050) Another significant result from the thermal expansion testing was that the expansion curve was found to be smooth and gradually increasing throughout the temperature range from 25-1000° C. This indicates that no phase transformations occurred throughout this temperature range and confirms that heat treatment is not necessary to achieve thermal dimensional stability.

Production Heats and SEM/EDS Examination
J0051J Based upon study of the fifteen experimental pours, two full size
production heats (750 lbs.) of the J73 alloy, Heats 4G28I (Trial 16) and 4G30K (Trial 17) were made for production validation of softer and harder versions of the alloy material. Trial 16 was targeted to be softer (low 40's Re) and Trial 17targeted to be harder (mid-40's Re). Preliminary investigations reveal thai the J73 alloy micros true lure is generally more desirable al lower carbon content; hence, a preferred valve seat material would limit carbon to no more than is absolutely necessary to achieve the desired hardness. Chemistry and hardness results for Trials 16 and 17 are below in Table 6:
[0052] Table 6. Composition of 750-pound Heats 4G28T (Trial 16) and 4G30K (Trial 17)

Trial Hcaifl C Mn Si Cr Mo W Co Fe Ni V HRc
16 4G28I 1.17 0.09 1.00 23.67 9.0O 11.02 =0.1 19.97 33.86 <:0.1 41,3
J? 4G3QK 1.34 0.10 f.M 21.26 9.18 10.12 O.U 20.5_1 37.82 «l 1 46.0
]0053) In studying the microstructure of heat 4G28I, it was found to be similar to the desirable results observed in 3G10XA (Trial 8, a lower carbon heat), AS such, heat 4G28I was utilized to carry out SEM/EDS examination of the alloy material. It was revealed that the distribution of non-eutectic reaction phase (likely a solid solution phase) was evenly distributed.
[0054] An SEM/EDS/WDS assisted phase characterization was carried out using a model of Hitachi S3600N scanning electron microscope. Based upon the information from the microstrucrural examination some initial conclusions could be reached. A typical SEM microstrucrural image of the alloy (4G281) at 2001IX magnification is depicted in Figure 3.
[0055] Three major matrix phases could be viewed in an SEM secondary electron image (Figure 3). The image was adjusted to show the three major phases by level of brightness (A= white, B= gray, and C= black) in Figure 3. It was evident that Phase B was the abundant solid solution matrix phase. The Phase B distributed in and between regions A and C which arc multi-phase eutectic reaction products

resulting from euteclic/peritectic reactions while the "island-like" portions of Phase B is likely a primary phase during the alloy casting solidification process. (0056/ The three phases observed in the alloy appear to be very consistent in composition. Phase A has the highest chromium and least tungsten content while Phase C has the highest tungsten and least chromium content among the three phases examined. The EDS result for the chromium rich Phase A is shown in Figure 4. (0057) To further verify that phase transformations were not occurring below 1200° F., two heats of the alloy were tested for dimensional stability. Two 5 piece groups of inserts were tested from each heal. One 5 piece group was as-cast (no heat treatment) while the other 5 piece group was heat treated (stress relieved) at 1450°F. for 4.5 hrs.
{0058] To conduct a dimensional stability test, the outside diameters (O.D.) of all inserts arc measured very accurately at two locations, 90° apart. They are then heated at 1200" F. for 20 hrs. followed by cooling in still air. The inserts are then cleaned and O.D.'s re-measured at the same locations as the initial measurements. The difference between the initial and final O.D. sizes are then calculated. An insert material is considered dimensionally stable if O.D. size change is less than 0.00025" per 1" of insert diameter. The insert diameter tested was ! .375" which allows for a maximum change of 0.00034" after heating to be considered dimensionally stable. Dimensional stability test results are as follows in Table 7:


Flint Wear Test Results IQ061| High temperature reciprocating wear tests in a Flint Model TE77 Tribomeler were carried out using reciprocating pin versus plate test. The testing condition included a 20 Newton applied load, a 20 hertz reciprocating frequency and a 1 mm stroke length at various test temperatures from ambient to 500°C. {0062] In the wear tests, the reciprocating pin is made of the insert matenal while the stationary plate is made of the valve material. Valve materials tested include nickel-basedInconel 75J, nickel-based Nimonic 80A, and cobaii-based Steiiite f. Insert materials tested include three heats of the J73 alloy (Heats 3E28XA, 3F20XA, and 3G01XA), as well as one heat of nickel-based material BX2 (Heat 311OXA), one heat of J3 (Heat 4C30A), and one heat of Jl 30 (Heat 4D14N) for comparative purposes. Cobalt-based J3 is currently one of the most successful materials to run with nickel-based and Steiiite 1 valve materials in the marketplace today. Iron-based .1130 is also currently successful in exhaust applications. BX2 is a nickel-based material representative of alloys disclosed in U.S. Patent 6,200,688. The composition of materials used for the wear testing is compiled in Tabic R.
|0063] Table 8. Chemical Composition of Insert Materials Used for Flint Wear Tests.

Alloy Heat No. C Mn Si Cr Mo W Co Fe Ni V Nh
J73 3E28XA 1.57 0.08 1.00 22.41 8.66 I0.5G 0.48 23.15 Bal. <0.1
J73 3F20XA 1.57 0.07 I.0J 22.46 8.5B 10.50 0.44 23.09 Bal. <0.i
J73 3G0IXA 1.61 0.08 0.91 22.56 8.68 10-65 <0.1 23.34 Bal. <0.l -
n 4C30A 2.29 0.22 0.75 29.97 - 11.95 Bal. 0.74 0.22 -
13X2 311 OXA 1.60 0.46 3.70 13.43 - 11.93 - 33.09 Bal. - -
JI30 4D14N 1.48 0.40 0.98 10.00 9.24 - - Bal. 0.99 1.32 1.97
[0064| The wear testing results are summarized in Tables 9 and 10. Tests are carried out within both the intake and exhaust insert temperature ranges with results organized accordingly. Some conclusions derived from the testing results can be summarized as follows:



10067] Conclusions based upon wear test results are as follows: (0068] The J73 alloy exhibits a better wear performance than B and &X2 when tested against nickel-based valve material Inconel 751. This enhancement in wear resistance occurred within both the intake and exhaust temperature ranges. [0069] The wear resistance of the J73 alloy against Stellite I within the exhaust temperature range appears to be improved with an increase in bulk hardness. Heat 3E28XA (Test 4) had the lowest total and pin wear in Plint tests. |0070] The J73 alloy outperforms BX2 when run against nickel-based valve materia] Nimonic 80A. BX2 shows significantly higher pin wear as well as ioial wear within both the intake and exhaust temperature ranges. (0071) The J73 alloy outperforms both J3 and J130 when tested against cobalt-based valve facing materials Stellite 1 within the exhaust insert temperature range. Significantly, the exhaust application is where Stellite 1 is most commonly used in today's marketplace.
[0072] The preferred embodiments are merely illustrative and should not be considered restrictive in any way. The scope of the invention is given by the appended claims, rather than the preceding description, and all variations and equivalents which fall within the range of the claims are intended to he embraced therein.

WHAT IS CLAIMED IS:
1. A nickel-rich wear resistant alloy comprising in weight %:
0.5 to 2.5% C
0.5 to 2 % Si up to 1 % Mn 20 to 30% Cr 5 to 15% Mo 5 to 15% W 15 to 30% Fe balance Ni.
2. The alloy of Claim 1, further comprising up to 1.5% each of Ti, Al, Zr, Hf, Ta, V, Nb, Co or Cu and/or up to 0.5% each of Mg, B or Y.
3. The alloy of Claim I, wherein C is 1.5 to 1.6%, Si is 1.0 to 1.1% and Cr is 20-25%.
4. The alloy of Claim 1, wherein C is 1 to 2%, Si is 0.75 to 1.5%, Cr i.s 22 to 25%, Mo is 7 to 12%, W is 7 to 12%, Fe is 22 to 25% and Ni is 25 to 40%.
5. The alloy of Claim 1, having a microstructure containing predominantly eutectic reaction phases, fine intermetallic phases and precipitation carbides.
6. The alloy of Claim 1, having a microstructure containing Cr, Ni, W rich intermetallic phases.
7. The alloy of Claim 1, having a microstructure containing uniform lamellar type eutectic solidification structures.

8. The aUoy of Claim !, having a micros tructure containing up to ~i.8% C and essentially no primary dendritic carbides or microstructure containing non-dendritic type primary carbides over 1.8% C.
9. The alloy of Claim 1, having a microstructure containing up to 1.5% C and solid solution phases encompassed by eutectic reaction products.
10. A valve seat insert comprising in weight %:
0.5 to 2.5% C
0.5 to 2 % Si up to 1% Mn 20 to 30% Cr 5 to 15% Mo 5 to 15% W 15 to 30% Fe balance Ni.
11. The valve seat insert of Claim 10, further comprising up to 1.5% each of Ti, Al, Zr, Hf, Ta, V, Nb, Co or Cu, up to 0.5% B and/or up to 0.5% Mg plus Y.
12. The valve seat insert of Claim 10, wherein C is 1.5 to 1.6%, Si is f .0 to 1.1% and Cr is 20-25%.
13. The valve seat insert of Claim 10, wherein the Fe content exceeds the Cr content by at least 0.5% and the Ni content exceeds the Fe content by at least 5%.
14. The valve seat insert of Claim 10, wherein the W content exceeds the Mo content.
15. The valve seat insert of Claim 10, wherein the W content exceeds the Mo content by no more than 2%, the Fe content exceeds the Cr content by no more than 5% and the Ni content exceeds the Fe content by no more than 15%.

16. The valve seat insert of Claim 10, wherein the insert is a cast insert.
17. The valve seat insert of Claim 10, wherein the insert has ari as cast hardness of at least about 40 Rockwell C, a compressive yield strength at room temperature of 95 ksi and/or a compressive yield strength at 800°F of at least 85 ksi.
18. The valve seat insert of Claim 10, wherein the insert exhibits a dimensional stability of less than about 0.5xl0"3 inches after 20 hours at 1200°F.
19. A method of manufacturing an internal combustion engine
comprising inserting the valve seat insert of Claim 10 in a cylinder head of the
internal combustion engine.
20. The method of Claim 9, wherein the engine is a diesel engine.
21. A method of operating an internal combustion engine comprising closing a valve against the valve seat insert of Claim 10 to close a cylinder of the internal combustion engine and igniting fuel in Lhe cylinder to operate the internal combustion engine.
22. The method of Claim 21, wherein the engine is a diesel engine.