Bbc Brown, Boveri & Company, Limited

Hans Rydstad

Robert Singer

Mohamed Youssef Nazmy

Gernot H Gessinger

Bernd Jahnke

Gunther Schroder

Roland Kunzli

A process for increasing the oxidation resistance and corrosion resistance of a component made of a dispersion strengthened superalloy by means of a surface treatment, the object of which in every case is to produce or retain a fine-grained surface zone (5) while the core zone (4) of the component in all circumstances is forced to form coarse grains during the final recrystallization annealing in the temperature range between the recrystallization temperature and the solidus temperature. A fine-grained surface zone (5) is produced by cold-working the surface zone (3, 5) by shot-peening, surface milling or pressing or by heating the surface zone (7) to a temperature about 100.degree. to 140.degree. C. below the recrystallization temperature by means of a laser (9) or an arc (10) while the core zone is kept at less than 900.degree. C., or by application of a 10 to 50 .mu.m thick nickel layer onto the surface followed by diffusion of the nickel into the surface zone (nickel-rich surface layer 14) of the component at a temperature below the recrystallization temperature. In each case, recrystallization annealing in order to establish coarse grains in the core zone (4) is finally carried out.

Process for increasing the oxidation resistance and corrosion resistance

Components (5) in a superalloy, in particular a dispersion hardened nickel based alloy, are connected together by pressure bonding in the solid condition with the greatest possible limitation of the overall deformation of the complete components (5) by lateral restraint (7), the actual bonding zone (6) having short-term intensive dynamic plastic flow imposed on it and, taking account of the deformation temperature, the local deformation rate .epsilon..sub.l and the local deformation .epsilon..sub.l referred to the bonding zone (6) are matched together in such a way that the driving force during the subsequent heat treatment of the complete workpiece above the recrystallization temperature is sufficient to force the formation of coarse grain under all conditions. It can then be assumed that, in general, the expression ##EQU1## h.sub.o =height of the bonding zone (6) before connection, h.sub.f =height of the bonding zone (6) after connection,

Method for connecting superalloy components

Components made of a dispersion-hardened superalloy are connected together by pressure bonding, the individual parts previously processed at their bonding surfaces only by milling, without fine machining such as grinding, electro-polishing, etc., being subjected before bonding to a heat treatment in the temperature range of between 60.degree. C. and 210.degree. C. below the recrystallization temperature for the purpose of reducing the driving force. During the subsequent coarse-grain heat treatment of the bonded workpiece, no sort of fine crystalline banding occurs in the bonding zone and the strength of the workpiece corresponds to that of the material before bonding.

Process for connecting components made of a dispersion-hardened

A fine-grained workpiece having improved mechanical properties is produced from a nickel-based superalloy by two-part forging, a blank being converted, in a first isothermal hot-forming step (curve b) above the solution-annealing temperature for the .gamma.'-phase (line a), into an intermediate form and the latter then being finally forged to give the end form in a second isothermal hot-forming step (curve c) just below the solution-annealing temperature for the .gamma.'-phase. For the first step, a degree of deformation .epsilon. of of at least 0.7 at a mean deformation rate .epsilon. of about 10.times.10.sup.-3 s.sup.-1 is required here. The second step is carried out at deformation rates .epsilon. which are one to two powers of 10 lower than those of the first step.

Process for producing a fine-grained workpiece from a nickel-based

A process and apparatus for achieving narrow workpiece tolerances in isothermal drop-forging, the relative movement of the two die halves (1, 2) in an xy plane perpendicular to the pressing direction z being measured and monitored by means of an optical measuring device (10, 11, 12, 14) or mechanical measuring device (14, 15, 16) and being corrected by means of a mechanical adjusting device (6, 17, 21, 23, 24, 25, 26) for one die half (2). A first workpiece is forged, and the divergence from the nominal value is measured, with the die halves (1, 2) closed, the die halves (1, 2) are opened, the first workpiece is removed, the position of one die half (2) is corrected, and a new workpiece is introduced and forged completely, without the workpiece having to be cooled and remeasured and without the die having to be cooled and reheated.

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Birmenstorf, Switzerland

Hans Rydstad