Lost wax moulding method with contact layer

1. A method of manufacture of a multilayer ceramic shell out of a master pattern of a part to be manufactured, said method comprising the steps of:

preparing a first slip containing ceramic particles and a binder, wherein the first slip comprises mullite flour in an amount ranging between 65 and 80 in weight %,

dipping the master pattern in said slip and forming a contact layer, and

depositing sand particles on said contact layer and drying said contact layer,

wherein said sand particles are mullite grains having a grain size distribution range between 80-250 micron, wherein the first slip does not contain any zircon and the first slip comprises a wetting agent, a liquefier and a texturing agent,

forming additional layers on said contact layer thereby forming a ceramic shell;

disposing of said master pattern thereby forming a ceramic mould;

baking said ceramic mould;

casting a metal part in said ceramic mould;

wherein said contact layer forms an interface between said ceramic mould and said metal part, and

wherein said additional layers comprise a mixture of alumina and mullite flours in amounts ranging between 45 and 95% in weight, and mullite grains in amounts ranging between 0 and 25% in weight.

2. A method according to claim 1 , further comprising selecting the wetting agent among polyalkylene fat alcohols or alkoxylate alcohols.

3. A method according to claim 1 , further comprising selecting the liquefier among the amino acids, ammonium polyacrylates or carboxylic tri-acids with alcohol groups.

4. A method according to claim 1 , further comprising selecting the texturing agent among ethylene oxide polymers, xanthan gums or guar gums.

5. A method according to claim 1 , wherein the binder is based on water-based mineral colloïdal solutions.

6. A method according to claim 1 , wherein said depositing comprises sprinkling the sand particles.

7. A method of manufacturing said part, said method comprising the method of claim 1 , and further comprising a step of solidifying metal with columnar structure oriented solidification.

8. A method of manufacturing said part, said method comprising the method of claim 1 , and further comprising a step of solidifying metal with mono-crystalline structure oriented solidification.

9. A method according to claim 5 , wherein the binder is based on water-based colloïdal silica.

10. A method according to claim 1 , wherein said additional layers include zircon particles.

11. A method according to claim 1 , wherein said metal part is a part for a turbojet engine.

12. A method according to claim 2 , further comprising selecting the liquefier among the amino acids, ammonium polyacrylates or carboxylic tri-acids with alcohol groups.

13. A method according to claim 12 , further comprising selecting the texturing agent among ethylene oxide polymers, xanthan gums or guar gums.

14. A method according to claim 13 , wherein the binder is based on water-based mineral colloïdal solutions.

15. A method according to claim 1 , wherein said master pattern is made of wax.

16. The method according to claim 1 , wherein said depositing of said sand particles is performed so as to control said after-baking porosity thereby controlling the shell mould's sensitivity to thermal shock to comply with casting conditions meeting stresses of a solidification method selected from the group consisting of an equiaxed solidification (EX), a columnar structure oriented solidification (DS) and a mono-crystalline structure oriented solidification (SX).

17. The method according to claim 16 , wherein the binder is a water-based colloidal solution and not an alcohol-based binder.

18. The method according to claim 1 , wherein said method is free of a step of including a ceramic based mat of reinforcing material in said shell mould.