CA1118618A - Age-hardenable iron-base alloy - Google Patents

Abstract

AGE HARDENABLE WELD DEPOSIT
ABSTRACT OF THE DISCLOSURE
An age hardenable iron-base alloy weld deposit consisting essentially of, in weight percent, Carbon 0.2 maximum Manganese 1.3 maximum Silicon 1.0 maximum Phosphorus 0.02 maximum Sulfur 0.02 maximum Chromium 3 to 10 Molybdenum 9 to 13.5 Cobalt 15 to 25 Nickel 0.3 maximum Iron balance wherein the ratio of (% chromium plus % molybdenum) to (% cobalt plus % nickel) is between about 0.75 and about 1.10. The weld deposit has superior gelling resistance and hot hardness, which are useful properties in hot extrusion dies and hot shearing blades which may reach temperatures as high as 1450°F in service.

Description

This invention relates to age hardenable iron-base alloy weld deposits. More particularly the invention relates to such deposits which provide superior galling resistance and hot hardness up to at least 1450F (790C). Our weld deposits are preferably applied to ferrous alloy base materials such as low alloy, carbon, mild and tool steels.
Many industrial applications involve metal-to-metal wear at high temperatures; examples of such applications are hot extrusion dies an`d hot shearing blades which may reach temperatures as high as 1450F (790C) in service.
Alloys used in such applications, either as the working parts or as surface layers on the working parts, should have good galling resistance and good hardness at working temperatures.
Heretofore, the most widely used alloys for applications such as those described above have been expen-sive nickel-base and cobalt-base alloys, the former typified by the wrought alloy INCONEL* 718 and the latter by commercial welding alloys classified by the American Welding Society (AWS) as ER CoCr-A and ER CoCr-C, which are applied as weld deposits on various base materials. More recently, alloys known as TRIBALOY 400** (cobalt base2 and TRIBALOY 700**
(nickel base2 have been introduced; in the heat treated condition these alloys contain large volume percentages of Laves phase intermetallic constituents. The TRIBALOYS are generally applied as powders to a base structure and then fused by the heat of an electric arc, although in experimen-* Registered Trademark of the International Nickel Co.** Trademark of the E,I. DuPont deNemours Co.

tal work they have been deposited using shielded metal arc welding electrodes.
The nickel and cobalt base alloys of the prior art, particularly the TRIBALOYS which contain high percentages of molybdenum, are characterized by extremely high cost, and therefore their use has been limited. Moreover, several of the nickel and cobalt base alloys of the prior art are prone to crack when applied as weld deposits, and this further limits their utility. Finally, the TRIBALOY type alloys require a rather long aging treatment in order to develop optimum properties, which adds to their-cost.
Another alloy suggested for possible use in high temperature metal-to-metal wear applications is a chromium-and cobalt-containing tool steel disclosed in U.S. Patent No. 3,508,912. However, this alloy is not balanced for use as a weld deposit; i.e., the patent disclosure does not teach weld metal composition necessary to obtain optimum hot hardness properties while avoiding excessive cracking.
Consequently, the alloy disclosed in the patent, while useful to some extent as a wrought product, has serious disadvantages when applied as a weld deposit.
~ e have discovered that by maintaining the analysis of an iron base alloy weld deposit within limits to be described hereinbelow, an age hardening alloy deposit can be produced with superior galling resistance and hot hardness, as well as freedom from cracking, age hardenability to levels greater than 55 Rc, machinability in the as-deposited condition, dimensional stability, good fatigue resistance, and a significantly lower cost as compared to cobalt-and nickel-base alloys of the prior art. With these properties our deposit can be used in many applications where far more expensive nickel-base and cobalt-base materials have heretofore been required, and this can be done without loss of service performance. Moreover, our deposit has superior service life compared to standard hot worked tool steel alloys and to alloys such as those disclosed in U.S. Patent No. 3,508,912.
In accordance with the present invention, there is provided an age hardenable iron-base alloy weld deposit consisting essentially of, in weight percent, Carbon 0.2 maximum Manganese 1.3 maximum Silicon 1.0 maximum Phosphorus 0.02 maximum Sulfur 0.02 maximum Chromium 3 to 10 Molybdenum 9 to 13.5 Cobalt 15 to 25 10 Nickel 0.3 maximum Iron balance wherein the ~atio of (% chromium plus % molybdenum~ to (% cobalt plus ~ nickel) is between about 0.75 and about 1.10.
Preferably, the deposit consists essentially of, in weight percent, Carbon Low as possible Manganese 0.1 to 0.8 Silicon 0.5 maximum Phosphorus Low as possible 20 Sulfur Low as possi~le Chromium 4 to 6 Molybdenum 11 to 12.7 Cobalt 16 to 21 Iron balance and the ratio of (% chromium plus % molybdenum) to (% cobalt plus % nickel) is between 0.90 and 1.05.
me deposit is particularly useful when applied to ferrous alloy base materials of the group consisting of low alloy, carbon, mild and tool steels.
To develop optimum properties, the deposit should be aged 6 hrs at 1050~F.
When applied using the shielded metal arc welding process we prefer the deposit to contain about 0.04% carbon, about Q.5% manganese, about 0.3% silicon, about 5% chromium, 35 about 11.9% molybdenum and about 18~ cobalt.
When our deposit is applied using a semi~automatic tubular electrode we prefer it to contain about 0.04% carbon, about 0.5% manganese, about a.3% silicon, about 5% chromium, about la% molybdenum and about 16% cobalt.

Our weld deposit is preferably applied as an overlay on ferrous base materials such as low alloy, carbon, mild, and tool steels. It is not entirely suitable for use on nickel base alloys, stainless steels containing nickel in excess of 6% by weight, austenitic manganese steels, or high carbon cobalt-base alloys unless a sufficient number of layers are deposited to obtain an essentially non-diluted overlay; excessive dilution of our deposit with such base materials causes a loss of its desirable properties.
The above stated analytical limits and relationships for our weld deposit are necessary to obtain the desired properties, and are based on the following described considerations:
Carbon should be kept as low as possible to avoid both the formation of high carbon martensite and the combin-ation of carbon with chromium and molybdenum, all of which tend to increase the hardness of our deposit in the as-deposited condition and thereby impair its machinability.
In addition, when carbon is high enough to form carbides with chromium and molybdenum the scale resistance and age hardening characteristics of our weld deposit are adversely affected and the important relationship between cobalt, chromium and molybdenum, discussed hereinafter, is interfered with. Finally, low carbon helps to insure good fatigue resistance and dimensional stability of the deposit over a wide range of temperatures.
Although manganese improves the crack resistance of our deposit, amounts over about 1.3% by weight have an adverse effect on its hot hardness characteristics, particu-larly above 1250F. In order to minimize such adverseeffects we prefer levels of manganese no greater than about 0.8% by weight.
As is common with most iron-base alloys, the phosphorus and sulfur levels of our deposit should be kept as low as possible to avoid damaging effects on crack resistance. We have set a broad limit of 0.02% by weight maximum for each of these elements but prefer that the levels be well below 0.02%.
Chromium improves heat and scale resistance, but it - ~1186~3 is a ferrltizer and as such tends to lower the crack resis-tance of our we]d deposit; to balance the two effects we maintain a broad chromium range of 3 to 10% by weight and we prefer chromium in the range of 4 to 6% by weight.
Molybdenum makes our deposit age hardenable because it combines with iron at aging temperatures to form an intermetallic constituent which we believe to be of the formula Fe2Mo; this constituent imparts galling resistance and hot hardness to the deposit at temperatures up to at 10 least about 1450F. However, high molybdenum levels adversely affect the crack resistance of our weld deposits, such that unacceptable cracking cannot be avoided when more than about 14% by weight is present. Consequently we maintain molybdenum levels broadly between 9 and 13.5% by weight and preferably 15 between 11 and 12.7% by weight.
Cobalt is the principal austenitizer of our weld deposit. As such, it provides the necessary metallurgical balance during welding to result in the formation of a low carbon ferritic matrix when the deposit reaches room tempera-20 ture' this matrix enhances the rapid formation of smallamounts of the Fe2Mo intermetallic constituent during the optimum age hardening treatment of the deposit ~6 hrs at 1050F [565C~. In addition, cobalt adds to the hot hardness properties, and to some extent to the scale resistance, of 25 our deposit. Weld metal cracking problems are encountered àt cobalt contents well above 25% by weight, but the upper limit of this alloying element is determined principally by cost factors; i.e., above about 25% the cost of cobalt tends to wipe out the economic advantage of our deposit over nickel 30 base and cobalt base alloys of the prior art. We maintain cobalt levels broadly between 15 and 25% by weight and we prefer cobalt in the range of 16 to 21% by weight. It should be noted that U.S. Patent No. 3,508,912 teaches that cobalt above 15% by weight is of no value and in fact has certain 35 adverse effects in the wrought alloy disclosed therein, whereas we have found that in our weld deposit cobalt above 15% is necessary to allow the use of high molybdenum content for optimum crack resistance, agin~ and hot hardness properties.

lli86~3 We have found that nickel adversely affects the hot hardness properties of our deposit and in sufficient amounts interferes with the age hardening mechanism, apparently by retarding the formation of the iron-molybdenum intermetal-lic constituent. To avoid these negative influences wemaintain nickel at residual levels, i.e., less than about 0.3% by weight, and for best results we keep nickel well below 0.3% by weight. Again it should be noted that in U.S.
Patent No. 3,508,912 nickel at levels of about 2% by weight is recommended to avoid heat checking in the wrought tool steel disclosed; as will be seen here`inbelow, nickel at similar levels in our deposit would cause unacceptable damage to the hot hardness properties.
Tungsten can be substituted for molybdenum on about a 2 to 1 basis, but the cost of tungsten is higher than that of molybdenum and use of tungsten even on a 2 to 1 basis is not accompanied by any improvement of properties over those obtained with molybdenum. We therefore do not use tungsten.
Certain elements such as vanadium, columbium, 2Q titanium and zirconium are occasionally used in small amounts in tubular welding electrodes. We have found that these elements promote cracking in our weld deposit, so they should only be used under strict control in residual amounts;
preferably we do not intentionally add any of these elements.
Aluminum promotes weld cracking and retards age hardening; therefore, although small amounts of aluminum are sometimes used in welding alloys, we do not use any aluminum in the deposit of our invention.
As is discussed more fully hereinbelow, the ratio (% Cr + % Mo) determines whether or not our weld deposit will (% Co + % Ni2 be satisfactorily crack-free. Our data indicate that ratios between about 0.90 and l.a5 eliminate fissuring entirely and that by maintaining the ratio between about 0.75 and about 1.10 the number and size of weld metal cracks formed will be small enough that commercial utility of the deposit is not impaired. Since the deposit of our invention is restricted to residual nickel levels, we ignore the nickel term in the ratio.
To evaluate the properties of our weld deposit and 111861~3 compare various embodiments thereof with other alloys used for similar service applications by the prior art, weld deposits were made of the alloys studied, except for two prior art alloys, noted hereinbelow, which were tested in wrought form. Each weld deposit was prepared using covered electrodes in which the core wire composition and alloy additions made through the covering, if any, were balanced to give the desired final weld deposit composition; such balancing is well known and commonly done in the welding art. The electrodes included a titania (TiO2) slag system typical of those known in the welding art as AC-DC.
Except as noted hereinafter, test specimens were prepared by depositing four layers of weld metal on a suitable base plate, commonly mild steel; with four layer deposits, however, the precise composition of the base plate is not critical, since the weld metal of the top layer, which was the actual metal tested, is essentially undiluted -i.e., the composition of the alloy in the fourth layer is derived solely from the covered electrode used.
In the data presented hereinbelow, certain chemical analysis figures are shown as estimated values; such estimates are based either on typical values obtained from prior analyses, applicable industry specifications, or published literature, or on calculations made using the overall electrode composition (and base plate composition in one casel and standard gains or losses in elements established from prior experience. Such estimations, commonly used by those skilled in the welding art, provide good representative analyses of weld deposits in cases 0 where actual analysis is not critical.
EXAMPLE I
Listed in Table I below are the chemical analyses of a group of alloy weld deposits whose age hardening and hot hardness properties were studied. Deposits No. 1 through 6 are deposits of our invention. The 0.1~ by weight estimated nickel represents a residual level, since no deliberate addition of nickel was made to any of Deposits 1 through 6. Deposit 7 is deposit of the invention to which increased manganese was added. Deposit 8 was a 2-layer 118~ 8 deposit on a base plate of INCONEL 718 (typically 52 Ni - l9 Cr - 3 Mo - 5 Cb - l Ti Bal. ironl. The analysis of Deposit 8 was calculated based on a typical dilution factor of 33.3% per layer - i.e., the tested deposit was a mixture of approximately 8/9 metal from the welding electrode and 1/9 metal from the base plate. Deposits 9 and lO had alloy balances within the teachings of U.S. Patent No. 3,508,912.

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Table 2 below shows the age hardening properties of six of the deposits of Table 1 after aging for 6 hours at 1050F.

Rockwell Hardness, ~c unless othe~wise in~icated Deposit No. As Deposited Aged 6 hrs.
at 1050F

2 45 62 10 5 36 ~ 60 8 86 Rb 89 Rb It will be noted from Table 2 that the deposits of the invention, Deposits 1, 2 and 5, as well as the alloys of U.S. Patent No. 3,508,912, Deposits 9 and 10, show good properties. Although the level of nickel present in Deposit 9, which is within the nickel range recommended by U.S.
20 Patent No. 3,508,912, does not appear to have damaging effe,cts on age hardening in that alloy, the results with Deposit 8, which contained an estimated 5.8~ nickel, show clearly that even relatively modest amounts of nickel in our alloys can have a damaging effect on both as welded 25 hardness and age hardening characteristics.
In Table 3 the hot hardness of the alloy weld deposits of Table 1 is shown; all deposits were aged 6 hrs at 105aF prior to hot hardness testing.

11~86~3 TA~LE 3 Hot Hardness at Indicated Temperature RC Unless Otherwise Indicated

3 O.S.* 52 46

4 55 44 31 O. S. * 54 24 06 O.S. * 51 24 7 O. S . * 39 21 8 T.S.** T.S.** T.S.**
9 - 55 44 92 Rb 15 * Off scale (too hard).
** Too soft to get reading As seen from Table 3, deposits of our invention, Nos. 1 through 6, retain good hot hardness even at 1450 F.
20 Addition of manganese, as in Deposit 7, results in damage to the hot hardness properties, particularly at the intermediate temperature of 1250F. Deposit 10, the low nickel version of the alloy disclosed in U.S. Patent No. 3,508,912, has reasonable hot hardness values, although it is considerably 25 lower in hardness at 1050F ahd 1250F than deposits of the invention. The adverse effect of nickel on hot hardness is clearly seen in Deposits 9, meeting U.S. Patent No.
3,508,912 and containing 2.8% nickel, and 8, substantially equivalent to our inventive deposit except for containing 3Q approximately 5. 8% nickel. It will be noted that increases in nickel content had significant adverse effects on hot hardness, especially at 1450 F; at higher nickel levels hot hardness of our deposit deteriorates at all temperatures.

The hot hardness properties of preferred deposits of our invention were compared with those of five commercially available cobalt and nickel-base alloys reputed to be outstanding for hot hardness up to 1450 F. Table 4 (below~
presents the chemical analyses of the alloys involved and the 111861~3 hot hardness test results. Deposits 11 and 12 are represen-tative of cobalt-base weld surfacing alloy deposits classified by the American Welding Society (AWS) as ECoCr-A and ECoCr-C respectively; these deposits were tested in the as-welded condition, the condition in which they are normally used.
Deposits 13 and 14 were experimental weld deposits formulated to provide compositions corresponding to TRIBALOYS 400 and 700 respectively; these deposits were aged for 24 hours at 1350F to develop maximum properties before testing. Finally, "Deposit" 15 was a sample of wrought INCONEL 71~ which had been heat treated as recommended by the manufacturer to develop optimum properties. It Will be appreciated that all of Deposits 11 through 15 are considerably more expensive than the deposits of our invention.

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,~ z * ~ m 11186'18 As will be seen from Table 4, weld deposits of our invention are generally equivalent or superior to the commercial alloys against which they are compared in hot hardness properties. Only the TRIsALOYS, Deposits 13 and 14, exceeded the deposits of our invention in hardness, and this only by a slight margin at 1450F. In general, it can be concluded from these tests that the deposits of our invention have hot hardnesses which are equivalent or superior to those of commercial alloys heretofore used in similar applications, and at significantly less cost.

Weld deposits of our invention are characterized by superior crack resistance. In Table 5 (below) the crack resistance of deposits of our invention is compared with that of six of the prior art deposits discussed in the foregoing examples. To compare crack resistance a two-phase crack test was devised.
- In the first phase of the test each deposit was applied to l/2-inch thick mild steel base plate in a series of single weld beads up to 4 layers high. Each layer was examined for evidence of cracking and a crack resistance rating (CRR) was assigned equal to the layer in whic~
cracking was found, if any; i.e., a deposit cracking in the first layer was given a CRR of 1, while one cracking in the fourth layer was assigned a CRR of 4. If a deposit did not crack during the first phase, it was then subjected to the second phase of the crack test Since the first phase consisted only of single bead layers on l/2-inch thick plate, which did not subject the deposit to high restraint, and since cracking tendency was further reduced for the deposits tested by using preheat and interpass temperatures of 400F or 600F, the latter tending to be more beneficial in this regard, the first phase was not considered to be very severe from a weld metal cracking viewpoint. Conse-quently, deposits which cracked during the first phase weredeemed to have very poor crack resistance However, the first phase did provide a means of evaluating relative crack resistance between the highly crack sensitive materials of the group tested.

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The second phase of the crack resistance test involved a restrained crack test (RCT), a much more severe test of the deposits studied. In the RCT, 1-1/4 inch by 2-1/2 inch by 12 inch mild steel base plate was used; because

5 of its thickness and the fact that it was heavily clamped, this plate offered fairly severe rigidity and thus caused much higher stresses in the weld metal than the plate used in the first phase; some of the severity of the test was counteracted by the fact that preheat and interpass practice 10 was used as in the first phase, but the RCT still remained a much more severe test than the first phase. With each deposit tested, 8-1/2 inch long weld beads were deposited in layers 4 beads wide~ up to a maximum of 3 layers (12 beads total); at the completion of each bead the deposit was 15 inspected visually for cracks. Generally any cracks observed visually were rather large, transverse to the weld bead and about l/2-inch or more long, and their appearance indicated that further welding would produce even more cracking.
Consequently, weld deposition was stopped whenever cracking 20 was visually observed in a bead. If no cracks were found visually throughout the entire 12 beads, the final RCT weld surface was ground and checked for cracks by fluorescent penetrant methods; results of such checking revealed that although extremely small cracks, or fissures, were often 25 missed in visual inspection, large cracks were found in all but one instance, noted below.
After testing, each deposit was given an overall crack resistance rating (CRR) based on the bead in which visually observable cracking occurred. If cracking 3Q occurred in the second RCT bead, for example, a CRR of 6 was assigned; this included a rating of 4 for successfully passing the first phase plus 2 for the two beads deposited before cracking in the RCT. If a deposit cracked in the 12th bead, the last possible bead of the RCT, it was given 35 a rating of 16 (4+121. For successful completion of the entire RCT (no visual cracks), a deposit was assi~ned a CRR
of 17.

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.~ ~ o As is evident from the above Table 5, the deposits of our invention were equal to or better than the other deposits tested in crack resistance. It should be noted that a deposit having a CRR of 6 or less was considered to be too crack sensitive for general commercial use; Deposit 11, one of the two which compared favourably with deposits of our invention, is known to be expensive and difficult to weld and therefore its commercial use is limited. Deposit 10 did not appear to have cracked during RCT welding, but a substantial number of large cracks were observed after fluorescent penetrant checking. Such large cracks would normally prevent completion of the RCT; why they did not in this case was not known. In any event, the 1/2 to l-inch long cracks found in Deposit 10 indicated that such deposit must be rated as crack sensitive and thus of limited use as a commercial welding alloy. It is believed that the cracking observed in Deposit 10 occurred because the total austenitizing alloy elements, principally cobalt, were too low, as will be discussed further hereinbelow.

We have found that even among those alloy weld deposits of the general type of our invention which have crack resistance ratings (CRR's) of 17 in the test of Example 3, some may be undesirable for commercial use because of fissures that are evident only upon fluorescent penetrant examination after the Example 3 test specimen is completed. In such deposits, optimum crack resistance is achieved by suitably controlling the relationship between the major ferritizers chromium and molybdenum and the major austenitizers cobalt and nickel; specifically, we have found that the value of the ratio ~% Cr + Mo)/(% Co + % Ni) appears to determine whether or not weld deposits of the invention will be acceptably free of fissures.
Table 6 lists chemical data and fluorescent penetrant check results for twelve alloy weld deposits having CRR's of 17 in the test of Example 3; the deposits include several of our invention and two alloys disclosed in U.S.
Patent No. 3,508,912. The data are arranged in order of increasing values of the ratio (% Cr + % Mo~/(% Co + % Ni), and they show that a ratio of from about 0.90 to about 1.05 appears to eliminate cracking entirely, and ratios between about 0.75 and about 1.10 restrict the formation of fissures to 15 or less, which we consider satisfactory for commercial 5 use. Note that the ratio of Deposit 10, discussed in Example 3, was 1.20, and the fluorescent penetrant check showed this deposit to be unacceptable for commercial use.

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111861~3 Additional study of the ratio (% Cr + ~ Mo) /
(% Co + % Ni) and its effect on crack resistance in deposits related to our invention indicated that the ratio is apparently effective only when molybdenum is below 14.0~ by weight; we believe that at higher molybdenum levels metallurgical changes occur that invalidate the relationship.
E~AMPLE 5 In order to test and rate relative galling resis-tance of deposits of our invention and prior art alloys used for galling resistance, a galling test was employed. In the test, a coupling was produced by contacting the surface of a metal button against that of a stationary metal block under a controlled stress; the button was then hand rotated slowly through one revolution, after which the mating surfaces were examined for galling at a magnification of lOx. The presence of metal build-up on the surface of either the button or the block indicated thatgalling had occurred. If galling was not found after the first test, new button and block area~
combinations were tested at successively higher loads until galling was found; when galling was discovered, it was confirmed by testing one more combination at a still higher load. Because light loads did not cause full area contact in this test, the actual contact area between button and block was measured at lOx magnification to convert the applied load to galling stress. The greater the stress to produce galling, the better the galling resistance.
Table 7 lists the results of five galling tests.
In each test wrought type 316 stainless steel was used as the rotated button because that alloy is widely used in applications where high temperature strength and galling resistance are important. As a standard for comparison wrought type 316 was also used as the stationary block for Test A. The other four tests utilized four different weld deposits for the stationary blocks; Test D utilized the deposit of our invention, while Tests B, C and E utilized commercial weld deposits generally considered to have good high temperature strength. Except for Test B, the tested weld deposits were essentially undiluted; the cobalt base ~i86i~

deposit of Test B was slightly diluted, since it was only two layers high on type 3Q4 stainless steel base plate, but the fact that it was a cobalt-base alloy appeared to make it tolerant of some dilution, as evidenced by the excellent test results obtained.

Galling Test Results WeldMaximum Test DepositStress to 10 No. Button Block LayersGall, Rsi A 316 316 - 4.0 B 316 - AWS ECoCr-A 2 45.0 (Deposit No.
12) 15 C 316 HASTELLOY C 8 2.0 D 316 Invention 638.0( ) (Deposit No.
1) E 316 TRIBALOY 700 435.0(-) (Deposit No.
14) (1) Values above 30 ksi are regarded to have excellent galling resistance (2) Test stopped before galling occurred.
Note from the results of Table 7 that in galling resistance the deposit of our invention is far superior to type 316 and to HASTELLOY* C (15 Cr - 16 Mo - 4 W - Bal.
Nickel), and is competitive with AWS ECoCr-A and TRIBALOY
700.
In summary, weld deposits of our invention provide improved properties over prior art alloys used in similar applications and are considerably less expensive to produce than most such alloys. While we have described certain present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied within the scope of the following claims.

* Registered Trademark of Union Carbide Corporation

Claims (6)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An age hardenable iron-base alloy weld deposit consisting essentially of, in weight percent, Carbon 0.2 maximum Manganese 1.3 maximum Silicon 1.0 maximum Phosphorus 0.02 maximum Sulfur 0.02 maximum Chromium 3 to 10 Molybdenum 9 to 13.5 Cobalt 15 to 25 Nickel 0.3 maximum Iron balance wherein the ratio of (% chromium plus % molybdenum)to (% cobalt plus % nickel) is between about 0.75 and about 1.10.

2. The weld deposit of claim 1 which contains, in weight percent, Carbon about 0.04 Manganese about 0.5 Silicon about 0.3 Chromium about 5 Molybdenum about 10 Cobalt about 16

3. The weld deposit of claim 1 or 2 which has been aged 6 hours at 1050°F.

4. The weld deposit of claim 1 consisting essentially of, in weight percent, Carbon Low as possible Manganese 0.1 to 0.8 Silicon 0.5 maximum Phosphorus Low as possible Sulfur Low as possible Chromium 4 to 6 Molybdenum 11 to 12.7 Cobalt 16 to 21 Nickel 0.3 maximum Iron Balance wherein the ratio of (% chromium plus % molybdenum) to (% cobalt plus % nickel) is between 0.90 and 1.05.

5. The weld deposit of claim 4 which contains, in weight percent, Carbon about 0.04 Manganese about 0.5 Silicon about 0.3 Chromium about 5 Molybdenum about 11.9 Cobalt about 18

6. A composite article comprising a base material having a weld deposit thereon, the base material selected from the group consisting of low alloy, carbon, mild and tool steels, the weld deposit consisting essentially of, in weight percent, Carbon 0.2 maximum Manganese 0.1 to 0.8 Silicon 0.5 maximum Phosphorus 0.02 maximum Sulfur 0.02 maximum Chromium 4 to 6 Molybdenum 11 to 12.7 Cobalt 16 to 21 Nickel 0.3 maximum Iron balance and having a ratio of (% chromium plus % molybdenum) to (% cobalt plus % nickel) between about 0.90 and about 1.05.