Stacking Spellblade

The Spellblade Items do stack in a certain way, however I would not recommend stacking them.

You basically have the damage component and with Iceborn Gauntlet there's also the CC/AOE component.

The damage component deals singletarget damage based on the following order:

Lich Bane > Trinity Force > Iceborn Gauntlet > Sheen

Also if you have an Iceborn Gauntlet the AOE effect will always appear on a Spellblade proc, even if you have a Trinity Force or Lich Bane.

Let's say you have the following Items:

Lich Bane, Trinity Force, Iceborn Gauntlet

If you use an ability and attack someone after that, you will Deal 75% Base AD + 50% AP Magic damage to the Primary Target while also creating a slow-field that deals 125% Base AD Physical Damage from Iceborn Gauntlet. If you sell your Lichbane, you will deal 200% Base AD Physical damage to the primary target (and again the AOE) since TF still has a higher priority over Iceborn.

As you can see the effects do stack in a certain way, however it's not recommended to actually stack the items. If you already have a trinity force, you should probably go for Frozen Heart (similar Stats) or Frozen Mallet (similar Utility) instead of an Iceborn Gauntlet.