Method for producing objects from iron—cobalt—molybdenum/tungsten—nitrogen alloys

Abstract

The disclosure relates to a production of a semi-finished product for a manufacturing of objects, particularly tools, from a precipitation-hardenable alloy having a composition in wt. % of Co=15.0 to 30.0, Mo up to 20.0, W up to 25.0, Fe and manufacturing-specific impurities as a remainder. To achieve an economical, highly precise production of objects or tools of the above alloy with reduced effort, it is provided to prevent a formation of ordered structures of the Fe atoms and Co atoms in the matrix of the type (Fe+(29Co))+approximately 1 wt. % Mo of the semi-finished product by a thermal special treatment, to thus improve a workability of the material.

Claims

1. A method for producing a semi-finished product for objects or tools from a precipitation-hardenable alloy material having a chemical composition in wt. % including: TABLE-US-00002 Cobalt (Co) = 15.0 to 30.0, Molybdenum (Mo) = up to 20.0, Tungsten (W) = up to 25.0, (Mo + W/2) = 10.0 to 22.0, Nitrogen (N) = 0.005 to 0.12, Iron (Fe) and manufacturing-specific impurities=remainder, the semi-finished product having a hardness of under 40 HRC, a toughness of greater than 16.0 J, the method comprising: subjecting the alloy material to a thermal special treatment to break up an ordered structure of (FeCo) atoms in a matrix of a type (Fe+(29Co))+approximately 1 wt. % Mo, the thermal special treatment comprising heating and annealing the material at a temperature between 600 C. and 840 C. for a period of more than 20 minutes and subsequent cooling at a cooling rate of less than 3.0, to alter the hardness of the material to under 40 HRC and to alter the toughness of the material to greater than 16.0 J, measured using impact work of unnotched samples K.

2. The method according to claim 1, wherein the semi-finished product is a powder-metallurgically produced material (PM material).

3. The method according to claim 1, further comprising a forming of the semi-finished product and a soft-annealing of the semi-finished product prior to the subjecting the alloy material to the thermal special treatment to break up the ordered structure of (FeCo) atoms in the matrix.

4. The method according to claim 1, wherein the semi-finished product has an elongation limit R.sub.P0.2 of less than 825 MPa, a tensile strength Rm of less than 1220 MPa, and an elongation at fracture AC of greater than 6.5% in a tensile test.

5. A method for producing a semi-finished product for producing objects or tools from a precipitation-hardenable alloy having a chemical composition in wt. % comprising: TABLE-US-00003 Cobalt (Co) = 15.0 to 30.0, Molybdenum (Mo) = up to 20.0, Tungsten (W) = up to 25.0, (Mo + W/2) = 10.0 to 22.0, Nitrogen (N) = 0.005 to 0.12, and Iron (Fe) and manufacturing-specific impurities=remainder, the method comprising: breaking up an ordered structure of (FeCo) atoms in a matrix of a type (Fe+(29Co))+approximately 1 wt. % Mo using a thermal special treatment comprising: heating and annealing the material at a temperature between 600 C. and 840 C. for more than 20 minutes, and subsequently cooling the material at a cooling rate of less than 3.0, to alter the hardness of the material to under 40 HRC and to alter the toughness of the material to greater than 16.0 J, measured using impact work of unnotched samples K.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:

(2) FIG. 1 shows the microstructure of an FeCo(Mo+W/2) N alloy;

(3) FIG. 2 shows the hardness as a function of the annealing temperature for the thermal special treatment of the semi-finished product;

(4) FIG. 3 shows the hardness as a function of the cooling rate; and

(5) FIG. 4 shows the FeCo ordered structures from neutron diffractometry.

DETAILED DESCRIPTION

(6) The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.

(7) The tests took place using samples made of an alloy having a composition in wt. % of:

(8) Co=25.2

(9) Mo=14.9

(10) W=0.1

(11) Mo+W/2=15.0

(12) N=0.02

(13) Fe remainder and manufacturing-specific impurities,

(14) and a hardness of 48 to 53 HRC, which were produced from a material manufactured according to the PM methods and hot-isostatically pressed and formed.

(15) A series of samples was soft-annealed at a temperature of 1185 C. and subsequently cooled at 24 C./h. After this soft-annealing treatment, the samples had on average the following measured values:

(16) Hardness of 41.2 HRC0.5 HRC,

(17) Impact bending work 14.5 J0.6 J,

(18) Elongation at fracture 4.8 A.sub.C0.2%=A.sub.C,

(19) Tensile strength Rm 1290 MPa20 MPa, and

(20) Elongation limit R.sub.P0.2 855 MPA10 MPa.

(21) FIG. 1 shows a structural image of the sample, wherein the matrix can be recognized as a dark region in which intermetallic phases (light) are intercalated.

(22) On other similarly treated samples, a thermal special treatment occurred at temperatures of 500 C. to 950 C. with an annealing time or at-temperature holding time of 40 min and a cooling rate of less than 0.4. The cooling rate results from the cooling time from 800 C. to 500 C. divided by 100.

(23) $=\frac{\sec }{100}$

(24) A special annealing with a temperature of 500 C. to 600 C. results in, as FIG. 2, Region 1 shows, hardness values of the material of 42 HRC. Higher annealing temperatures up to 850 C., as can be seen from Region 2 and Region 3 of FIG. 2, lower the material hardness to values up to 38 HRC, wherein an additional increase in the annealing temperature (Region 4) produces a significant hardness increase to over 44 HRC.

(25) If the samples are kept at 800 C. for 30 minutes after a special annealing and subsequently cooled with different values, average hardness values of 41.18 HRC at 10 decreasing to 38 HRC at 0.4 and lower are achieved, as is illustrated in FIG. 3.

(26) To determine the ordered structure of atoms in crystalline solids, the diffraction of neutron beams at the periodic lattice can be used. By a periodical arrangement of atoms in the FeCo lattice, what are known as superstructure reflections occur. The superstructure is the (100) reflection in the ordered B2 lattice.

(27) On soft-annealed samples A and on such samples with an additional thermal special treatment B, an ordered phase of the Fe atoms and Co atoms in the matrix was determined by neutron diffractometry using a STRESS-SPEC diffractometer with a Ge 311 monochromator, wavelength of 16 nm. FIG. 4 shows contrastingly a neutron diffractogram (100) of the superstructure/ordered-structure reflections of the samples A and B in comparison.

(28) A largely disordered FeCo structure is clearly present in a matrix B specially treated according to the invention.

(29) It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present disclosure. While the present disclosure has been described with reference to an exemplary embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present disclosure in its aspects. Although the present disclosure has been described herein with reference to particular means, materials and embodiments, the present disclosure is not intended to be limited to the particulars disclosed herein; rather, the present disclosure extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.