java 8 sum all values of two int arrays with each other

int[] ar1 = {1,2,3};
int[] ar2 = {1,2,3};

Output:

{2,3,4,3,4,5,4,5,6}

I tried something like this:

IntStream.range(0,ar1.length).map(x -> IntStream.range(0,ar2.length).map(y -> ar1[y]+ar2[x]));

but this does not work:

Type mismatch: cannot convert from IntStream to int.

How can I sum every value of ar1 with every value of ar2 in Java 8 using streams?