FR2488536A1 - PROCESS FOR THE MANUFACTURE OF SEMI-PRODUCTS FROM PLATINUM RELEASED IN DISPERSION - Google Patents

Abstract

A.PROCED BY CHEMICAL PRECIPITATION OF A MIXTURE OF PLATINUM AND NON-PRECIOUS METAL OXIDES, SINTING OF THE PULVERULENT MIXTURE AND MECHANICAL TREATMENT IN A SEMI-PRODUCT. B. PROCESS CHARACTERIZED IN THAT, IN ORDER TO OBTAIN THE SINKED BODY, THE POWDER IS SUBJECTED TO SINTERING (IN BULK) IN A FIRST STAGE AT A TEMPERATURE OF 700 TO 1100C, AFTER WHICH THE FRITTED BODY IS MACHINED AT THE LATHE AT 180, AND IN A SECOND STAGE, IT IS SUBJECTED TO A DEFINITIVE SINTING AT A TEMPERATURE OF 1300 TO 1600C. C. PROCESS APPLICABLE TO OBTAINING PLATINUM PLATES WITH CORROSION AND OXIDATION RESISTANCE AND HIGH MECHANICAL RESISTANCE.

Description

-1 2488536

  The invention relates to a method for

  manufacture of semi-finished products from platinum annealed

  Persion with oxides of non-precious metals and / or other metals of the platinum family, by common chemical precipitation of the components, production of a sintered body from the pulverulent mixture, optionally oxidation of the non-precious metal components Subsequent processing into semi-manufactures Precious metals and their alloys, in particular platinum metal and its alloys, have wide applications in cases where high resistance to corrosion or high temperature oxidation is required. . A disadvantage of these materials, however, is a resistant

  relatively low mechanical temperature at high temperature.

  As a result of many tests have been carried out to harden and compare the precious metals and their alloys, by addition of inert materials in an oxidizing atmosphere

  as for example oxides with a high melting point.

  Thus, it is possible, for example, to mechanically mix the fine platinum powder with a fine-grained powdery oxide, and to treat the mixture according to the powder metallurgy. The reproducibility of the properties of a material thus obtained is however only unsatisfactory, and the improvement for example of the creep resistance of such a material at high temperature is relatively low compared to the material without additive, because according to this process it is very difficult to obtain a homogeneous distribution of particles

of oxide in platinum.

  It was also proposed to raise

  the creep resistance of platinum at high temperature by subjecting it after alloying with a metal whose oxide

  a very high formation temperature, a dispersed annealing

  internal oxidation at temperatures between 901 and 14000 C. By this method it is possible

  high tensile strength and hardness at ambient temperature

  biante, also a high resistance to creep at temperatures

high levels.

  The diameter of the oxide particles thus obtained by internal oxidation, is of the order of a few microns so that the effect of dispersion annealing that it obtains is relatively small. Due to the low oxygen diffusion rate in platinum metal, this also takes

  a lot of time to get a fully oxidized material.

  It is also known to perform the incorpo-

  treatment of the hardening particles by simultaneous precipitation from saline solutions, by evaporation of the solutions which contain the two components, or by spraying these solutions in a flame. Other processes are surface oxidation of alloy powders, by combination of a deposit

  by electrolysis, and electrophoresis.

  All these methods have a disadvantage is that their implementation is quite complex and expensive,

  without a substantial improvement of the properties being obtained.

  during the common precipitation of platinum and non-precious metals from solutions, if we obtain a homogeneous distribution of the components in the precipitated powder, However, we obtain, by conventional after-treatment by means of calcination of the powder to 8000 C, pre.ssage into a body, sintering and semi-product forming, products which have a tendency to form bubbles during calcination, and their

  implementation is therefore limited.

  The object of the invention was therefore to provide a process for the production of semi-products from platinum annealed in dispersion with oxides of non-precious metals and / or other platinum-based metals, by chemical precipitation in common of components, production of a sintered body from the powder mixture, optionally oxidation of the non-precious metal components and subsequent processing into a semi-finished product,

  to obtain a product that is not prone to forma-

  bubbles during calcination.

  For this purpose, the process of the invention is characterized in that, in order to obtain the sintered body, the powder is subjected to bulk sintering in a first step at a temperature of 700 to 11000 C, after which the sintered body is machined in turn at 1800, and in a second step, it is subjected to a definitive sintering at a temperature of 1300 to 16000 C. Preferably, the sintering takes place in the first step at 8000 C, and in the second step, at 1600 C. Sintering can be carried out in air, hydrogen or under vacuum. Sintering under argon has, however, been particularly advantageous, in particular

in the second step.

  Bulk sintering means that the platinum powder has not undergone pre-compaction by mechanical or isostatic pressure prior to sintering, as has hitherto been customary for the production of equivalent sintered bodies. The beam obtained by chemical precipitation is introduced into a

  crucible and shaken only slightly.

  As the starting material, preference is

  A platinum powder containing 0.05 to 1% by weight of zirconium oxide. However, it is also possible to use other precious metals powder such as palladium, iridium, rhodium, ruthenium or osmium, or mixtures of these metals, and other oxides of non-precious metals, such as for example titanium, thorium, beryllium, aluminum or tantalum, alone or as a mixture. The amounts of added oxide-forming metal are generally between 0.05 and 5% by weight, calculated as oxide. The subsequent conversion of the sintered body into a semi-finished product is preferably carried out by means of a forging treatment at a temperature of 1200 to 14000.degree.

  until the body reaches a higher density.

  less than 80% of the theoretical density.

  It is advantageous to then perform another cold forming, with intermediate annealing at 10000 C, in air. It has proved advantageous here to modify the direction of forming several times, particularly in case of rolling. The semi-products thus obtained do not present,

  after annealing at 14000 C in the air, even after 100 hours, no

  dance to the formation of bubbles. The creep resistances for hours (14000 C, air) are between 6 and 8.5 N / mm2, hardness HV3, after 1000 hours (14000 C, air), between 560 and

660 N / mm2.

  The invention will be better understood by means of

the example described below.

  - 1 kg of a mixture of a platinum powder with about 0.16%

  of zirconium oxide, which was obtained by simultaneous precipitation

  The mixture, known from hexachloroplatinic acid and zirconium nitrate, is introduced into a graphite crucible and stirred for 1 to 2 minutes. Under an argon pressure of about 1025 mbar, the furnace is first started in the first sintering stage for about 6 hours at a temperature of 8000.degree. kept at this temperature for 2 hours. The sintered body is then machined to turn 180, and it undergoes subsequent sintering in a second step, on a ceramic support. For this purpose, the temperature is raised in 4 hours at-1600 C, and maintained at this level during

3 hours.

  This gives a body with a sintering density of about 60%, which is subsequently treated by forging at 12000 C under hydrogen, until a

  density of 90% of the theory. The manufacture of sheet metal

  by cold rolling with intermediate annealing (20 minutes,

10000 C, air).

  The sheet thus manufactured does not exhibit any bubbles even during 1000 hour annealing (14000 C, air), and the creep resistance is 7.5 N / mm 2 (100 h,

1400 C, air).

Claims (6)

  1.- Process for the manufacture of semi-   produced from platinum recycled in dispersion with oxides of non-precious metals and / or other metals of the platinum family, by common chemical precipitation of the components, production of a sintered body from the mixture spray, the case oxidation of the non-precious metal components and further processing into semiproducts, characterized in that, in order to obtain the sintered body, the powder is subjected to sintering (in bulk) in a first step at a temperature of 700 to 1100 C, after which the sintered body is machined in turn at 180, and in a second step it is subjected to definitive sintering at a temperature of 1300 to 160 ° C.   2.- Process for the preparation of semi   products according to claim 1, characterized in that the friage takes place in the first step at 800 C, and in the second step at 1600 C.   3. Process according to claims 1 and 2   Characterized in that as sintering atmosphere is used argon.   4.- Process according to any one of the   Claims 1 to 3, characterized in that   as a mixture of powder, platinum with 0.05 to 1% by weight of zirconium oxide.   5. Process according to any one of   Claims 1 to 4, characterized in that the sintered body is   subjected, under a hydrogen atmosphere, to a forging treatment up to a density greater than 80% the theoretical density.   6. Process according to any one of   Claims 1 to 5, characterized in that the sintered body   forged is subjected to cold drilling, with intermittent annealing