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perfecting materials
Vacuum brazing: Good to know – production and reparation of gas turbine components by vacuum brazing

Insight in our daily business:

How to repair turbine components!

Flying and land-based gas turbine components are heavily loaded and quite expensive. For this reason maintenance of turbine components is an important contribution to conserving resources and cost savings. First figure demonstrates the guide vane of a jet turbine made of Inconel after repair brazing. Within the individual guide vane segments entire blades are replaced as well as surface defects of still operational blades repaired.

For replacement the worn blade is removed by eroding, the new blade is introduced and fixed by tag welding and finally brazed to the outer and inner ring. For repair of surface defects, i.e. cavities and cracks, a blend of filler and parent metal powder is applied as a paste to the cleaned blade surface. During the following brazing process the filler metal melts, alloys itself with the parent metal powder and fills up the damaged area. Besides the requirements of no cracks and high temperature resistance especially distortion has to be controlled carefully because the vane is already machined to final geometry. For such service conditions boron-free, high-melting nickel based filler metals are utilized.

How to improve efficiency of gas turbines!

A good example how to join thin-walled to very solid components is demonstrated by shown part of a land-based gas turbine.

Such shroud segments are assembled to an entire ring which is touched by the rotating blades, especially during start-up. To minimize the gap between blade tip and rotor housing and consequently improving turbine efficiency so called honeycomb seals are used. During start-up and operation the blade-tips can seat into the sealing. The shroud consists of a martensitic Cr-steel. To avoid damage of the turbine blades the honeycomb is made of superalloy foils. The requirements to the brazing process and resulting joint are manifold. On the one hand the honeycomb structure has to be firmly bonded across the whole area to avoid detachment during operation. On the other hand the honeycomb structure has to be prevented from erosion.  This phenomenon occurs if the parent and filler material are similar in terms of chemical composition. To ensure high-temperature resistance a nickel based filler metal is used which, in the liquid state, can solve/erode the solid honeycomb foils. For this reason filler metal amount, brazing temperature and time have to be strictly controlled. Such requirements can be fulfilled only within a well maintained vacuum furnace with excellent temperature uniformity. Brazing and hardening of shroud segments are performed in the same process.


Listemann Technology AG
Ober Au 38
LI-9487 Bendern
+423 375 90 10

Listemann AG
Sulzer Allee 25 
CH-8404 Winterthur
+41 52 245 18 50

Listemann Polska Sp.z o.o.
ul. Biskupińska 23
PL- 30732 Kraków
+48 12 6534 230
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