Artifact improvement chance

Level	Chance
0 -> 1	100%
1 -> 2	70%
2 -> 3	70%
3 -> 4	50%
4 -> 5	40%
5 -> 6	40%
6 -> 7	40%
7 -> 8	30%
8 -> 9	30%
9 -> 10	20%

source:4r4m

This info is relevant for korean servers, please, pay attention.