CA1077748A

CA1077748A - Method of producing high carbon hard alloys

Info

Publication number: CA1077748A
Application number: CA262,405A
Authority: CA
Inventors: Gordon R. Lohman; James E. Hansen
Original assignee: Amsted Industries Inc
Current assignee: Amsted Industries Inc
Priority date: 1976-01-22
Filing date: 1976-09-30
Publication date: 1980-05-20
Also published as: SE7700125L; FR2338998A1; BR7607793A; MX3941E; IN145539B; ATA971576A; GB1573052A; JPS5290405A; AT376704B; BE848124A; FR2338998B1; DE2645574A1; IT1069824B; ES452934A1; AU497666B1

Abstract

METHOD OF PRODUCING HIGH CARBON HARD ALLOYS
Abstract of the Disclosure A method for forming high carbon hard alloys using powdered metal techniques wherein the carbon content of the atomized powdered metal particles is minimized and the carbon content to achieve the desired composi-tion is provided by blending carbon or carbon contain-ing powder with the powdered metal particles prior to compaction and sintering. The compact may be sintered just above the solidus temperature of the alloy.

Description

~ .

1~777~8 METHOD OF PRODUCING HIGH CARBON ~RD ALLOYS

The present invention relates to an improved method for making high carbon hard alloys by the use of powder metallurgy techniques and, in certain embodiments thereof of forming a heat or quench hardenable steel. The pre-sent invention also relates to an improved sintering method for powder metallurgy techniq~les.
The ~rior art discloses the making of a heat harden-able steel using powder techniques wherein an atomized pre-alloyed powder is compressed and then sintered in the presence of a carbonaceous reducing agent. The sintered product is also mechanically worked so as to effect a density substantially equivalent to the steel in its cast and wrought state.
Alloys of the type to which the present invention relates contain carbon ranging between about 0.6 to 5.0% by weight. In accordance with the teachi.ngs of the prior art ? the metal powders employed are alloyed prior to sintering. That is to say the base metal or metals are melted with the alloying elements to form the desired alloy and thereafter atomized.
The alloyed powders containing the requisite carbon content to form the desired alloy are extremely hard and abrasive. The prior art teaches that these hard I~MI1:sa 3-3-76 -~ Case 5545 ~777~

powders are not easily compressed In fact, it is believed that even after annealing, the powders retain their abrasiveness and hardness and thereby limit cold compactibility. It should be readily apparent that this prior art method has the disadvantage of pro-ducing an abrasive powder which required annealing to render it more suitable for compaction.
By the present invention, it is proposed to provide an improved method of forming a high carbon, hard alloy using a powder metal technique which is simpler to per-foL^m and which will yield uniform predictable results.
Another feature of the invention is directed to a method of sinterin~ a Powder metal high carbon~ hard alloy to substantially full density.
In one embodiment of the invention, the method is directed to the formation of a high carbon, heat harden-able steel.
This is accomplished by a method wherein a powdered metal is formed by atomization of metal composition con-taining the elements for forming the desired alloy, butlow in carbon content which may be maintained below 0.2%
by weight. The resulting powdered metal thus formed with the carbon maintained at a minimum is readily com-pactible without annealing. The carbon required to obtain th~ dQsired analysis is provided by lampblack or graphite

- 2 -I~MF:sa 3-3-/6 Case 5545 ~4~3 whlch is blended with the powder metal. The blended powder metal and carbon ;s then compacted and sintered so that the lampblack or graphite is diffused into the metal powder. Additional carbon to that required to achieve the desired alloy analysis may be provided to compensate for oxygen reduction which occurs during sintering as a result of the reaction of carbon with oxide fo~ned during atomization of the powder metal.
The lampblack or graphite added may vary from about 0.6 to 5.0% by weight of the blend to be compacted:
of this amount of carbon from about 0.6 to 4.5% by weight is added to achieve the desired product analysis while 0% to about 0.5% carbon may be included to com-pensate for the oxygen reduction~
The metal powders blended with the lampblack or graphite form hard and abrasion resistant products, and contain alloying quantities of one or more of ~he elements chromium, vanadium, tungsten and molybdenum so that a hard carbide is formed with such element or elements. In preferred embodiments, the alloy contains a quantity of iron so that complex carbides of iron with one of the elements, chromium, vanadium, tungsten or molybdenum may be formed.
In accordance with another aspect of the invention, compact is sintered at a ~emperature just above the EJB-kjc 6/~6/79 ~7 ~

solidus temperature for the alloy. It has been found that a "high density" alloy will result; that is, as herein used~
of such density that no further densification as by peening or forging is required for use. Density in the range of 97V/o to 100% of theoretical density may be considered high density. It has been found that at such sintering tempera-ture, distor~io~ is minimal (i.e. the parts retain their ~;
shape) and dimensional shrinkage is predictable so ~hat finished products can be produced and held within the desired dimensional tolerances without further processing.
In particular, the present invention provides the method of producing a high carbon, heat and abrasion resistant alloy having a final composition including at least 1% of at least one of the elements of the group con-sisting of chromium~ vanadium, molybdenum and tungsten, the elements of this group being characterized by a major portion of the carbides thereof remaining undissolved at elevated temperatures, said method comprising the steps of:
atomizing a melt having an initial composition which includes at least 1% by weight of one of the elements of the group consisting o chromium, vanadium, molybdenum and tungsten and a carbon content of less than 0~2~/o by weight thereby to limit the formation of the carbides of said elements of said group to a level substantially below that present in said final composition and thereby to form a cold compactible powder, ~ .

, EJB:kjc 6/~5/79 ~ ~ 7 ~7~ ~

blending said cold compactible powder with carbon particles of sufficient quantity to fo~n a blend which has a final composition of at least about 0 6% by weight carbon, without further treatment compressing said blend into a green compact blank at a pressure in excess of 20 tsi;
and heating said green compact blank at a temperature and for a time sufficient to cause carbon diffusion and thus to provide carbides of at least some of the elements of said group of a quantity sufficient to impart hardness and abra-sion resistance to said final composition.
Brié Description of_the Drawin~
The drawing is a phase diagram in relation to the carbon content of a typical high carbon hard alloy, and specifically for a M2 tool steel having by weight 6%
tungsten, 5% molybdenum, 2% vanadium and 4% chromium.
Description of Specific Embodiments Tool Steels One suitable alloy class ormed comprises heat hardenable alloy tool steels wherein the powder metals to be blended with the lampblack or graphite have the follow-ing analysis:

-4a-RM~:sa 3-~-76 --~ Case 5545 ~777~L8 Carbon About 0.2%
Silicon About 1%
Manganese About .25%
Sulfur About O04%
(0,05 to 0.5% for free machining gr~des) Phosphorus About 0.04% maximum Chromium About 2 to 9%
Vanadium About 0.5 to 7%
Cobal~ Optional up to about 15%
Tungsten Optional up to about 24%
Molybdenum Optional up to about 12%
Iron Balance Atomization of the composition is carried out in the well-known manner in which a molten stream of the composition is poured through an area wherein it is im-pinged by a fluid such as liquid, as for example water;
or gas, as for example steam; nitrogen; compressed air and the like. The impingement serves to disperse the falling molten metal into find particles which drop into a liquid medium such as water wherein the particles are quenched. The size and contour of the particles may be controlled by conventional and well-known means. The composition of the metal powder thus formed in accordance with the present invention has less than about 0. 2~/o carbon content. In the absence of a substantial quantity of carbon in the particles, the formation of any signi-ficant amount of hard carbides in a ferrite matrix does ,.
not occur in the prior art.

I~MF:sa 3-4-76 _ Case 55[~5 ~ ~ 77~7~ ~

The required carbon, in the form of lampblack or graphite to achieve the desired tool stelel c~mposition is then blended with the metal powder. This blend of powder metal and carbon contains at least sufficient carbon to produce a compacted product having the desired tool steel analysis. To this end, at least about .6%
by weight of lampblack or graphite is blended with the powder metal. Generally the amount of lampb]ack or graphite added will be in excess of that required to achieve the desired analysis in the final composition.
The excess carbon is used during sintering to reduce the oxides formed on the particles during atomization.
The blend of the metal powder and carbon is cold compacted at compacting pressures of about 2810 to 8425 kg per sq. cm. in a die having a suitable lubricant on the die wall. As an alternative, the powder may be mixed with a lubricant, for example 3/4% by weight Acrawax "C" made by Glyco Chemical Co., and no die wall lubrication is necessary. The shape of the article to be formed from the powder metal blend determines the particular method of compaction or die shape to be used.
Conventionally, the compacted ~end would initially preferably be sintered in a hydrogen or non-oxidizing atmosphere or in a vacuum at a tempera~ure ranging bfftween about 1093C and 1205C for sintering to occur.

~faJe ~k - 6 -EJB~kjc 5/26/79 55~5 ~7 ~

In accordance with the present invention it has been ound that the graphite will diffuse into the powder metal par-ticles. The sintered compacts may thereafter be peened ~o densify the surface and thereby to minimize oxidation which occurs during the preheating for forging as more fully to be explained hereinafter. The compacts which are intended for use as a tool, for as example as a gear hob 3 tool bit and the like are further compr~ssed into greater density and shaped into the desired configuration by forging. The compacts are preheated in suitable atmosphere for forging at a temperature o~ between about 1093C to 1177C (2000F
to 2150F) and thereafter forged. After forging, the articles are heat treated at temperatures and periods to achieve a desired range of hardness. The final hardness and mechanical characteristics are achieved by well-known quench hardening and tempering procedures.
In accordance with another feature of the present invention, sintering can be carried out just above the solidus temperature where there is a sufficient amount of liquid phase present so that a high density sintered com-pact will result. Thus it has been found that test sinter-ing various heats of M2 tool steel between the solidus and liquidus temperature will result in a high density alloy as follows:

.. , RMF:sa 3-4-76 Case 5545 ~7~7~

% Theoretical Heat Chemical Analysis of M2 Heat _Density No. C Mn Si Cr V W Mo 1227C 1238C
5 hrs. 5 hrs.
1.04 .071.0~ 4.0 ~.2 6.2 4.7 97 2 1.15 .06.76 3.8 2.2 6.5 4.8 97

3 1.16 .051.22 3.8 2.3 ~.8 4.9 98 97

4 1.18 .031005 3.9 2.3 6.5 5.0 98 97 The following are specific examples of the method 10 of the present invention applied to tool steels:

EXAMPLE N0. 1 1. A heat of steel corresponding to an AISI M2 high speed steel composition except for carbon content was water atomized and screened into a -100 mesh powdered metal having the following analysis:

C -0.023% Mo-4.60%
Mn-0.24% V -1.87%
Si-0.68% W -6.48%
P -0.009% 02-0.15%
2. The powdered metal was blended with 1.00% by 20 weight natural graphite to achieve the necessary carbon content to form the desired tool steel composition. The powdered metal was cold compacted in a closed die at 8425 kg per sq. cm. using a molybdenum disul~ide grease as a die wall lubricant. The powder metal was compacted into blanks of 8.9 cm in diameter by 3.2 cm high. The density of the blanks was about 6.5 gm/cc or 80% of the theoretical density.

~Ml':sa 3-4-76 Case 5545 ~ 7 7 ~

3. The blanks were heated in a hydrogen àtmosphere to 982C, held for one-hal hour to equalize temperature, and sintered at 1149C for one hour at temperature.
4. The sintered blanks were shot peened for 10 minutes to densify the surface and minimize internal oxidation during preheating of the blanks for forging.
S. The blanks were preheated in air for forging in the temperature range of 1093C to 1149C.
6. They were forged on a high energy rate forging press to a final density of 8.09 gm/cc (99.3% theoretical).
7. Thereafter the forged blanks were annealed at 871C - 900C for four (4) hours and allowed to slow cool. Annealed hardnesses ranged from Rockwell C 15-25.
8. The blanks were preheated for hardening at 816C for 30 minutes, austenitized at 1232C for 4 minutes, and oil quenched.
9. The blanks were double tempered at 552C for two ~2) hours.

Hardened properties included-Hardness - Rc 65 Intercept grain size - 25 The resulting tool steel is capable of being used as gear hobs, cutters, mills and the like.

_ 9 _ - RMF:sa 3-4-76 Case 5545 ~777~L~

EXAMPLE N0. 2 1. A heat of steel corresponding to an AISI M2 high speed (represenked by Heat No. 3 in the preceding table) except for carbon content was water atomized and screened into a -100 mesh powder having the following analysis:

C -0.03% Mo-4.~/O
Mn-0.07% V -2.2%
Si-1.04% W -6.2%
Cr-4.0% 02-.20%
2, The powder was blended with 1.15 percent by weight natural graphite (1.0% to meet analysis specifi-cation and .15% to compensate for oxygen reduction) O.l~h molybdenum disulfide lubricant was also added to the blend with 1% Acrawax C.
~ . The powder was cold compacted at /U2~ kg per sqO cm. into blanks 2.54 cm in diameter by 2.54 cm thick.
The density of the blanks was about 6.3 gm/cc or 77% of theoretical density.
4. The blanks were burned off at 482C for 60 minutes under an atmosphere of nitrogen ~U gr per sq. cm.
gage pressure).

5. The compact was then sintered at 1238C for 5 hours in a vacuum. The sintering temperature selected was just above the solidus line into the liquid ~
austenite ~ carbide re~ion of the phase diagram. As appears from the drawing, the solidus point for a similar steel at the final carbon content of 1~04~/o is ~MI:sa 3-4-76 Case 5545 ~L~777~8 approximately 1227C; the liquidus point is approxi-mately 1427C.

6 Cooling from the sintering temperature was carried on by g~s fan cooling with low dew point ni-trogen.
A heat density tool steel product resulted with minimum distortion of shape such that a fillished pro-duct is produced within usable tolerances without further processing of the sintered compact. Holding at an intermediate temperature to equalize the tem-perature throughout the load during sintering, as in Example No. 1, did not appear necessary. The density was 7.9 gm/cc or about 97% of theoretical.

EXAMPLE N0. 3 1. A heat of steel corresponding to an AISI M2 high speed tool steel composition exc~pt for carbon content was water atomized and screened into a -40 mesh powder having the following analysis:
C -0.052% Mo-4. 91~/o Mn-0.33% V -1.93%
Si-0.92% W -6.48%
Cr-4.46% 0~-0.20%
2 The -40 mesh powder was bIënded with 1.10 per-cent, by weight of natural graphite, ~.95% to meet analysis specifieation and .15% to compensate for oxygen redu~ion). The powder blend was processed as ~ollow~:

I~MF:sa 3-4-76 -- Case 5545 ~ ~ 7 7 ~

3. The powder was cold compacted at 7022 kg per sq. cm. using a molybdenum sulfide grease as a die wall lu~ricant into blanks of the following dimensions:

Dia Height Weight Density

7.62 cm 12.7 cm 3.62 kg 6.3 gm/cc (7~/O of theoretical) 4. The blanks were sintered in vacuum as described below:

a) 982C for one (1) hour to equalize the ternperature throughout the load.

b) 1149C for one and one-half hour at tem-perature.
c) Cooled to 871C and held for one hour.

d) Rapid cool to room temperature using ni-trogen backfill system.

e) Vacuum level maintained at 100 microns or less.
5. Blanks were shot peened for 15 minutes to densify the surface.
6. Preheated for forging in air at 816C-871C

and then at 1093C-1149C for 10 minutes maximum time.
70 High energy rate forged to 8.05 gm/cc (99/O
theoretical~.
. .
EXAMPLE N0. 4 A lot of water atomized powder having the sarne flnalysls as described in Example No. 3 was processed as follows:

RMF:sa 3-4-76 Case 5545 ~177'79~3 1. Blended with 1.10 pereent by weight natural graphite (.95% to meet chemistry specifieation and .15%
to aeeount for oxygen reduetion), plus 1 percent by weight "Aerawax C" as a lubrieant, 2. The powder blend was eold compacted at 7022 kg per sq. em. into a blank 7.62 cm. long by 1.27 em.
wlde by 2,29 em. thick bar weighing about 140 grams.
The green density was 6.5 gm/cc (80% theoretical density).
3. The blanks were burned off at 538C for one (1) hour in nitrogen.
4. The blanks were sintered in vacuum as described:
a) Heat to 982C hold for thirty (30) minutes.
b) 1149C - sixty ~60) minutes e) 760C - 2 hours d) Baekfill with nitrogen 5. Shot peened for six ~) minutes.
6, Preheated in 1232C furnace for 5 minutes in argon to heat blanks to 1149C - 1177C.
7. Forged in a closed die under 3 conditions, no lateral flow, 10% lateral flow, and 20% lateral metal flow. Final densities were:

. . .
Condition Density No flow 7.96 gm/ee (97.3% theoretical) lOV/o lateral flow 8.00 gm/cc (98.1% theoretical) 20% lateral flow 8.05 gm/cc (99% theoretical) ', ' , ' '' ' ~ . ' :

1~777~13

8. Annealed at 900 C for four (4) hours to a hardness of Rockwell C20.

9. Preheated for hardening at 816 C - 871 C for thirty (30) minutes, then austenitized at 1218 C for 4 minutes and oil quenched.

10. Tempered 552 C for two hours.

11. Cooled in liquid~nitrogen for 30-60 minutes.

12. ~ouble tempered 552 C for two (2) hours.
EXAMPLE N0. 5 A heat of steel corresponding to an AISI T15 high speed tool steel composition except for carbon content was water at~mized and screened into a -100 mesh powder having the following analysis:

C -0.042% V -4.25%
Mn-0.26% Co-4.71%
Si-Q.76% W -12.71%
Cr-4.05% 02-0.45%
The -100 mesh powder was blended with 1.90 percent by weight natural graphite (1.5% to meet chemistry spec-ification o~ tool steel desired and .33% to compensate for oxygen reduction)~ The blended powder was processed as follows:
1. The blend mixed with 1 percent by weight "Acrawax C" to act as a lubricant.
2. The powder was cold compacted at 7022 kg per ~MI~:sa 3-4-7G
Casc 5545 ~777~8 sq. cm. into 1.27 cm. x 7.62 cm. x 2.29 cm. bars weighing 140 grams. The blank density was 6.4 gm/cc (77% theo-retical density).
3. The lubricant was burned off at 538C for one ~1) hour in nitrogen.
4, The blanks were sintered in vacuum maintained at 100 microns or below as described:
a) Heated to 982C for thirty (30) minutes.
b) 1149C - sixty (60) minutes.
c) 760 C - ~wo (2) hours.
d) Backfill with nitrogen.
5. Shot peened for six (6) minutes to densify to surface to minimize internal oxidation during preheating for forging.
6. The shot peened b]ank was preheated between about 1149C - 1177C in an inert atmosphere.
7, Forged 8. Annealed 9. Hardened and tempered EXAMPLE N0. 6 A blend of powder having the chemical analysis as Example No. 3 was processed as follows:
1. Blended with 1.3 percent Cby weight~ natural graphite and 1 percent (by weight) "Acrawax C" for lubrication.

RMl~:sa 3-4-76 Case 5545 ~17779L~

2. Cold compacted at 7022 kg per sq. cm. into 2.54 cm. diameter by 2.03 cm. thick slugs, weighing 45 grams to pro~ide a density of 6.3 gm/cc or about 77~/O
of theoretical density.
3. Burned off 538C for one hour in nitrogen.
4. Sintered as follows:
Slugs were inserted into a hydrogen at~
mosphere furnace at 1238C, held one hour, and rapid cooled. The result was a high density, finished product with usable ~o-lerancesg having a density of 7.9 gm/cc or about 97% of theoretical density.

High Carbon Stainless Steels Another suitable steel alloy formed is a heat har-denable, high carbon stainless steel such as that used for cutlery corresponding to an AISI 440C steel. The steel is characterized by a high carbon content in the range o about .6 to 1.25% by weight and a high chromium content in the range of about 12 to 27% by weight. The steel is processed in similar manner as the tool steel described above.
A heat hardenable high carbon stainless steel may have the following composition:

RMl:sa 3-4-76 Case 5545 ~ 7 7~ ~ ~

Carbon About 0.5 to 1.25%
Manganese About 1.0% maximum Silicon Abou~ 1.0% maximum -Chromium About 12% to 27%
Molybdenum About 0.75% maximum Iron Essentially balance The following is a specific example of the method of the present invention for producing a heat treatable stainless steel 440C steel:

EXAMPLE N0. 7 1. A heat of steel corresponding to an AISI 430 stainless powder was water atomized and screened into a ~100 mesh powder metal~ having a composition correspond-ing to the desired 440C stainless steel except for car-bon content. The powder metal had the following analysis:
Carbon - .02%
Manganese - .17%
- Silicon - .98%
Chromium - 16.2%
Iron - essentially balance 2. The powder metal is blended with 1.00% by weight natural graphite to achieve carbon content to form the desired heat treatable stainless steel composition. A
molybdenum disulfide grease is used as a die wall lubri-cant. The powder metal is then cold ~ompacted in a closed die at 7022 kg per sq. cm. into blanks 8.89 cm. high.
3, The lubrican~ was burned off between 427C to 649C for one hour in nitrogen.
4. The blanks were then sintered in a vacuum at RMF:sa 3-4 76 - Case 5545 ~L~777~

982C for 10 minutes and then at 1205C for 60 minutes, with a partial pressure of nitrogen of 500 microns The blanks were then cooled in nitrogen atmosphere.
5. Thereafter the sintered blanks were hardened by heating to 1010C, holding for 30 minu~es at tem-perature, rapidly cooling to room temperature followed by heating to a temperature between 150C and 205Cl holding for 120 minutes and cooling to room temperature.
The properties of the sintered blanks included:

Density 6.1 gm/cc 79% of theoretical density Particle Hardness Rc 58 The heat hardenable, high carbon st~inless steel according to the present invention is suitable for cutlery and other purposes.

EXAMPLE N0. 8 Compacted blanks were prepared and the lubricant burned off in like manner as set forth in Example No. 7 above.
The blanks were then vacuum s;ntered at 1310C, 20 jU5~ above the solidus ~emperature, with a partial pressure of nitrogenO
High density products were produced with good dimenslonal control.

~MF:sa 3-4-76 Case 5545 ~77~48 Non-Ferrous AlloYs The process according to the present invention may be applied to high carbon non-ferrous base alloys which have the necessary alloying components to form the hard carbides of such elements as chromium, vanadium, tungsten and molybdenum. Iron also will form hard carbides and may be a desired alloying element of an essential.ly non~ferrous base alloy.
One alloy which may be made by the present method is a nickel-chromium alloy known commercially as Eatonite 10 and having a final composition as follows:

Carbon About 2 0 to 2.75%
Manga~ese About .025%
Silicon About 1.5% maximum Chromium About 27 to 31%
Nickel About 37 to 41%
Iron About 7% maximum Tungsten About 14 to 16%
Cobalt About 9 to 11%

1. A heat of alloy known as Eatonite but with carbon omitted was water atomized and screened into a -100 mesh powder metal having the following composition:

Carbon .02%
Manganese . 024%
Silicon 0.86%
Chromium . 29.8%
Nickel 39 3%
Iron 4.1%
Tungsten 15.1%
Cobalt 10.4%

rr~ P~

~MF:sa 3-4-76 Case 5545 ~ ~777~

2, The powder was blended with 2,5% by weight natural graphite and 1% lubricant such as Acrawax "C".
The powder metal was cold compacted in a closed die at 8425 kg per sq. cm. The powder metal was compacted into blanks of 2.54 cm. in diameter and 0.95 mm thick.
3. The lubricant was burned off at 538C for 60 minutes in nitrogen.
4, The blanks were sintered at 1238C for 120 minutes.
The properties of the blanks included:

Particle Hardness Rc 47 to 53 Density 7.22 gm/cc, 81%
theoretical density

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. The method of producing a high carbon, heat and abrasion resistant alloy having a final composition including at least 1% by weight of at least one of the elements of the group consisting of chromium, vanadium, molybdenum and tungsten, the elements of this group being characterized by a major portion of the carbides thereof remaining undissolved at elevated temperatures, said method comprising the steps of:
atomizing a melt having an initial composition which includes at least 1% by weight of one of the elements of the group consisting of chromium, vanadium, molybdenum and tungsten and a carbon content of less than 0.2% by weight thereby to limit the formation of the carbides of said elements of said group to a level substantially below that present in said final composition and thereby to form a cold compactible powder, blending said cold compactible powder with carbon particles of sufficient quantity to form a blend which has a final composition of at least about 0.6% by weight carbon, without further treatment compressing said blend into a green compact blank at a pressure in excess of 20 tsi; and heating said green compact blank at a temperature and for a time sufficient to cause carbon diffusion and thus to provide carbides of at least some of the elements of said group of a quantity sufficient to impart hardness and abra-sion resistance to said final composition.

2. The method as defined in Claim 1 wherein said initial composition includes at least 1% by weight iron.

3. The method as defined in Claim 1 wherein the alloy is an iron base alloy.

4. The method as defined in Claim 1 wherein said alloy is a heat hardenable tool steel.

5. The method as defined in Claim 4 wherein the final composition falls within the following analysis ranges by weight:

6. The method as defined in Claim 1 wherein said alloy is a heat hardenable stainless steel.

7. The method as defined in Claim 6 wherein the final composition falls within the following analysis ranges by weight:

8. The method as defined in Claim 1 wherein the alloy is a nickel base alloy.

9. The method as defined in Claim 8 wherein the final composition falls within the following analysis ranges by weight:

10. The method as defined in Claim 1 wherein said sintered and compacted powder blank is mechanically worked to attain substantially full density.

11. The method as defined in Claim 1 wherein said carbon consists of one of the group selected from lampblack and graphite.

12. The method as defined in Claim 2 wherein said carbon consists of one of the group selected from lampblack and graphite.

13. The method as defined in Claim 3 wherein said carbon consists of one of the group selected from lampblack and graphite.

14. The method of Claim 1 wherein said heating step comprises heating said compacted powder to a tempera-ture between the solidus and liquidus temperatures.

15. The method of Claim 5 wherein said heating step comprises heating said compacted powder at a tempera-ture of about 1093°C to 1177°C (2000°F to 2150°F).

16. The method as defined in Claim 2 wherein the conversion of said elements from said group consisting of chromium, vanadium, molybdenum and tungsten includes conver-sion of at least some of said iron into complex carbide of iron with at least one of said elements from said group.