Thanks,
i did that using a XY chart on render line mode using two different datasource for each year with 2 different series you can customize, once you have different seriex you create different xAxes and yAxes for each of them .
Is important also to calculate the range minimum and maximum ob both charts,
First calculate the maximum and minimum of each chart so later you calculate the max and min of both.
This way you can overlap as many charts ad you want.
Cheers.