exaust manifold broken

After just 24000 km only , the manifold of the exaust has given a metallic sound , then i open the cover and one ofthe nuts was broken off creating a hole in the manifols of 18 mm , then i taken out my welding set and weld it up , coated wit hhigh temperature spray coating , seems to be fine now , but very irritating on the issue, as our Sevice centre here do not repair it , instead ask you to change the manifold of a cost about 190 RM , something here is not rigth and has to change.
hope you will be more lucky then me.
RGDS