the answer is no....
the only way is to pre pay for excess luggage, or if in a big group maybe speak to the area/regional manager of airline and c if he/she can give u any extra, he/she is the only person that can give u more than 15kgs above ur ticket if he wants..
the alowance for all classes is as follows
economy = 20kgs
club = 30kgs
first = 40kgs
most airlines will give an extra 5-10kgs as a good will gesture at the time of check-in...
hope this helps