IRL I fear the answer all depended very much on exactly what weapon you were using. Katanas, as a great favourite the world over, were not used in the way that western swords were - and ergo reacted differently to a good clout.
Although very strong (due to the process of manufacture) a katana was used almost like a rapier in a duel. Swords would barely touch, and and nicks would be carefully buffed out after combat.
Two Handed swords (Greatsword is prolly the closest in DnD terms) were actually blunt weapons
A manual was uncovered not long back from crusade days, that was a training book for using the greatsword and involved such manuevers as 'gripping the blade' to slam the sword into an enemies face. This was probably as likely to 'nick' and chip as a katana, but it mattered a little less.
Swords that you want to keep sharp - katanas, rapiers, short-swords - would require constant care. Sharpening and cleaning (if you ever get to hold and admire a true to goodness
n century samurai's katana
don't breathe on it! ) would have been a daily routine.
As for the 'when you stirke something hard with it' query - again each sword was made for its field
Eastern weapons were ideal against eastern armour - which was often made of laquered plates, or laquer and mail. The blades were sharp enough to 'slice' through this armour with barely a scratch.
Western armour, of course, was the equivalent of todays main battle tanks. Bolts/arrows could puncture them, but cutting through them was a bloody nightmare. Hence two handed swords actually being blunt crushing weapons (and the invention of the lance), it was far easier to bludgeon that full plate into your opponent than to cut through it into your opponent.
Hope that gives you a bit of an idea, but - I fear - each weapon has it's own uses and reactions to a good smacking. You may have to look up the specifics.