Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
  • C22C27/04—Alloys based on tungsten or molybdenum
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/045—Alloys based on refractory metals
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S75/00—Specialized metallurgical processes, compositions for use therein, consolidated metal powder compositions, and loose metal particulate mixtures
  • Y10S75/95—Consolidated metal powder compositions of >95% theoretical density, e.g. wrought
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12014—All metal or with adjacent metals having metal particles

Definitions

• the alloy has been found particularly suitable for die casting molds to be used in casting ferrous metals as well as non-ferrous metals.
• the alloy composition has a molybdenum content of at least 90 percent by weight, a nickel content range between 2 and 8 percent by weight, a copper content between 0.5 and 2 percent by weight and may include minor amounts of other alloying metals such as iron, silicon and manganese.
• a liquid phase sintering method of preparation has been found to optimize the final properties of these alloy compositions.
• Tungsten alloys have been found particularly useful as lamp filaments for very high temperature operation while molybdenum and its alloys have also been found generally useful for lamp parts operated at lower temperatures. Tungsten alloys have also been used as mold and core materials in the casting of aluminum, brass and even ferrous metals.
• a ternary alloy of molybdenum containing approximately 0.6 weight percent zirconium and 1.25 weight percent titanium has also been employed heretofore in molds and cores for use in ferrous and non-ferrous casting processes.
• a molybdenum-base alloy with physical properties such as low thermal expansion and high thermal conductivity needed for application as a die casting mold has several distinct additional advantages compared with a tungsten-base alloy.
• the lower density of molybdenum provides a lower cost material of construction in the aforementioned application.
• the easier machinability of molybdenum compared with tungsten provides a further economic advantage for a molybdenum alloy. If tungsten is substituted for molybdenum in a refractory metal alloy composition, on the other hand, there is increased brittleness of the resultant material which is undesirable.
• a new class of molybdenum-base alloys having a novel crystalline structure which can be machined readily and possesses the desirable mechanical and physical characteristics for high temperature applications, especially in die casting processes.
• a new class of molybdenum-base alloys having a crystalline structure which consists of a particulate phase of essentially molybdenum and a matrix phase of a copper and nickel solid solution wherein said alloy has a molybdenum content of at least 90 per cent by weight, a nickel content range between 2 and 8 percent by weight, a copper content between 0.5 and 2 percent by weight, and which may include minor amounts of other alloying metals.
• Alloys of the present invention also exhibit isotropic mechanical properties which is attributable to a method of preparation that does not include mechanical working of the alloy product such as by extrusion, forging, rolling and the like.
• a pressed compact is first prepared from a uniform mixture of fine metal particles having the desired final composition, the pressed compact is heated to the sintering temperature for said composition in order to form a liquid phase of the nickel and copper present in the composition having some molybdenum dissolved therein, the heated compact is maintained at the Sintering temperature for a time period sufficient to produce a density of at least percent of the theoretical density for the particular composition, and the sintered compact is cooled rapidly to provide the final product.
• the pressed compact can be prepared from a uniform mixture of all metallic elements in the alloy composition or from a powdered mixture which includes a prealloy composition of some or all alloying elements being added to finely divided molybdenum powder.
• Preferred alloy compositions'of the present invention contain 95 percent by weight or more of molybdenum with the balance of the composition comprising primarily nickel and copper in a weight ratio of one or more parts nickel to parts of copper.
• the weight ratio of nickel to copper in the alloy composition is preferably 2-4- but does not exceed 6.
• the time period at which the pressed compact is maintained at the sintering temperature and the cooling rate therefrom have also been found to exert an influence upon the final properties of the alloy product.
• a time period from 1 to 3 hours at the sintering temperature range above specified provides the desired physical and thermal characteristics.
• Subsequent cooling of the sintered product at. a relatively fast rate such as can be obtained by quenching or by immediate exposure of said product to the ambient atmosphere provides an alloy having the desirable strength, hardness and ductility for good machinability. When such alloy has been machined into casting molds, it was found possible to obtain several thousand repetitive casting cycles when pouring various type steel compositions without experiencing severe damage of the molds.
• the present alloys further exhibit a yield strength of at least 100,000 psi at room temperature range and a yield strength of at least 60,000 psi at 540 C.
• the above reported properties dictate the importance of a proper time-temperature relationship in the method of preparing the present alloys.
• the alloy compositions of the present invention all have a two-component structure which consists of a particulate molybdenum component, that is, individual discrete molybdenum crystals in a densely packed relationship which is surrounded by a matrix component whose constituents are essentially copper and nickel in solid solution with molybdenum being dissolved in the solid solution.
• the molybdenum crystals which constitute the particulate component of the alloy crystalline structure can be further characterized as having a boundary layer of dissolved nickel by reason of the solubility of nickel in molybdenum at the sintering temperatures employed to prepare the alloy.
• the above alloy was prepared by starting with a-powdered mixture of the metallic elements in the proportions specified which were blended in a V-cone blender for one hour.
• the molybdenum powder selected had an average particle size of 3.5 microns.
• the average particle size of nickel and copper powders used was 2.5 michamber at a travel rate of approximately 13.5 in/hr then removed immediately for cooling by exposure to the ambient atmosphere.
• the initial presintering treatment has not been found essential in providing an acceptable material but was employed to increase the mechanical strength of the pressed compact sufficiently to withstand the subsequent sintering technique.
• the alloy product exhibited a density of 9.9 gm/cc along with a Rockwell C hardness in the range 30-34 and a bend angle of 5 at 22 C.
• EXAMPLE 2 To illustrate the utilization of different starting materials inpreparing alloy compositions of the present invention, a commercially available prealloy powder containing 29.3 copper, 0.005 carbon, 0.98 silicon, 0.74 manganese, 0.008 sulfur, 0.8l iron and the balance nickel was sifted through a 325 mesh U.S. screen size screen prior to blending with powdered molybdenum. The carbon and sulfur components of said prealloying material are considered at the impurity level hence do not form essential constituents of the final alloy composition.
• a powder mixture was next prepared having 95 parts by weight molybdenum and 5 parts by weight of the aforementioned prealloy material and pressed at approximately 34,500 psi to form a number of same size compacts for sintering treatment. More particularly, the pressed compacts were all given a presintering step at 800 C to l,000 C for 2 hours in a hydrogen atmosphere then followed by exposure to various sintering temperatures and sintering time periods reported below in Table l. Measurements made-upon the physical properties for each alloy product are also reported in said table.
• the powdered mixture was placed in a rubber mold and hydropressed at approximately 34,500 psi to provide a pressed compact for sintering.
• the sintering was accomplished by first heating the compact to l,000 C in a wet hydrogen atmosphere for a 1 hour time period followed by heating to approximately 1 ,4 00 C for an additional 45 minute time period in the same atmosphere to form the crystalline structure previously described.
• the final sintering was accomplished in a conventional manner wherein the pressed compact was pushed mechanically through the heated furnace It can be noted from the above measurements that a presintering treatment below l ,300 C does not provide a density within 95 percent of the theoretical density which is calculated to be 10.147 gm/cc for the particular alloy composition selected and there is an accompanying loss in ductility as well as mechanical strength of the final alloy.
• the cooling rate expressed in the above table as slow was obtained by leaving the heated samples in the sintering furnace chamber upon completion of the reported sintering time period with the cooling rate being established by ordinary cooling of said chamber upon removal of heat.
• the cooling rate reported in the table as fast was obtained by removing the samples from the sintering furnace chamber at the end of the sintering time period reported in the table and cooling the samples by exposure to ordinary ambient conditions. The faster cooling rate can be seen to improve ductility of the final product which renders the material more generally useful.
• a casting die fabricated from an alloy having the composition consisting essentially of a particulate phase of molybdenum having dissolved nickel, with a matrix phase of a copper and nickel solid solution having dissolved molybdenum, wherein said alloy has a molybdenum content of at least percent by weight, a nickel content between 2 and 8 percent by weight, a copper content between 0.5 and 2 percent by weight and which may include minor amounts of other alloying metals.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Powder Metallurgy (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=22497973

Family Applications (1)

Country Status (5)

Cited By (3)

Families Citing this family (2)

Citations (6)

• 1971
  • 1971-05-10 US US00141958A patent/US3770392A/en not_active Expired - Lifetime
• 1972
  • 1972-05-04 DE DE19722221814 patent/DE2221814A1/de active Pending
  • 1972-05-05 IT IT23968/72A patent/IT955230B/it active
  • 1972-05-10 BE BE783311A patent/BE783311A/xx unknown
  • 1972-05-10 FR FR7216655A patent/FR2139399A5/fr not_active Expired

Patent Citations (6)

Also Published As

Similar Documents