Welcome to Librarium Online!
No, he gets a 4+ armour save and a 4+ cover save. Adding eavy armour is useless because he gets a 4+ save for being on a bike anyway.
If you add cybork bodies (you will need a painboy in the unit for this) he will receive a 5+ invulnerable save and the Feel No Pain special rule. Expensive, but handy. If you have a Warboss in your army (on bike or not) you can take your nob biker squad as a rock hard (albeit pricy) troops choice which is mobile and can hold objectives. This has won me a battle or two.
Milkyj is correct. Armor never stacks. Nob bikers get a 4+ armor and 4+ cover save from the bikes, but you should always give them a painboy and the 5+ invulnerable save as well, since they can't use a cover save in close combat.
For the record, this is how I like to equip nob bikers:
6-7 Nob bikers w/2-3 powerklaws, painboy, cybork, waaaugh banner, 2-3 combi-skorchas, bosspole
I usually don't attach the warboss to the nob bikers, as it seems like overkill. I still use a warboss in the list, so the nobz count as troops, but I usually attach the warboss (with bike, powerklaw, cybork, attack squig, and combi-skorcha) to a unit of 5 regular warbikes w/nob, powerklaw, and bosspole.
"Any job worth doing, is worth doing with a powerklaw."