As said before, the non-keychained ones = probably, but the keychained ones= probably not. Sora's Keyblades have taken a lot of attacks in KH1 and KH2. I believe the keychains only change the appearance, strength, and magic of the Kingdom Key (The second ones in Drive forms just manifesting from a part Sora's heart, or something like that) to support my next guess.
In KH1, Sora blocked Riku's attack when Riku (possessed by Ansem) was about to beat Sora to a pulp and tried to hold the Dark Key down on him. That should've caused some stress.
In KH2, Roxas was also planning on beating Sora to a pulp for some orange juice too. They kept clashing blades and pushing down on each other until Roxas finally got Sora cornered and tried beating Sora's Key until it broke/slipped from his hands to win. Not to mention in KH2, that fight against Shan-yu (I don't know if this counts), you had to keep steady while he tried pushing Sora saying "You can't over power me sucka!" (lol). That also should've put some stress on it too.
Not to mention all the guarding against attacks, opening chests (when he could just use his hands), and any other things Sora used his Key for should've worn the Keyblade down too, but all of it didn't (the chets thing, maybe not a lot). If a non-keychained "Keyblade" can break just from being frozen and broken by a rock, then it can't be real.
Buuuuut, maybe a Keyblade against another, a fake, a sword, or any Heartless or Nobody weapons alike aren't strong enough. I keep thinking the Kingdom Key just might break someday. Maybe in another game they make about Sora (not the next one)!