For the past week or so Destiny 2 has been running on its Forsaken expansion pre-patch, but now that the whole shebang is live, we know a little more about how future infusions will work. Even minute infusions like purples into purples (epics) for just a scant few power levels require Masterwork Cores, an item introduced after the launch of Destiny 2.
To get them you’ll have to dismantle new Destiny 2 Year One items (obtained after the patch, so your old vaulted items won’t work) or purchase them from Spider, the new Fallen vendor that you’ll meet roughly an hour into the expansion. The other change involves the requirement of planetary materials, something that was present in the original Destiny. So for example in this case for the weapon in the gallery below, you’d need Dusklight Shards from the EDZ for this infusion.
There are a few concessions though. General activities will allow you to earn materials, so you don’t exactly need to go on Sparrow errand runs to slowly farm them (Spider also sells them). Also, given the new weapon system overhaul, it’s easier to infuse stuff now.
Source: Destructoid PSA: Destiny 2 requires more materials for infusions now, so be thrifty