If you're asking about equipment in general, after WW2 (and any war, for that matter), excess equipment was either:
- Gifted/sold to other nations
- Mothballed and later either re-entered service or scrapped
- Outright discarded/scrapped
- Maintained in service
Perhaps the most telling example of this is in the US Navy. Using the US Navy's official ship level data, we see on August 14th, 1945, the US Navy had 6,768 warships including 23 battleships and 28 fleet carriers.
We see that by June 30th, 1946, that became 10 battleships and 15 fleet carriers. And by June 30th, 1947, that became 4 battleships and 14 fleet carriers.
The battleships, having become obsolete during the war, saw them go through a variety of results. From the US Navy list of battleships you can see that:
- The older battleships were decommissioned in short order after the war and put in the Navy Reserve Fleets (essentially mothball fleets), and many weren't sold for scrap until the late 1950s/1960s.
- Some, like the USS Nevada, were sunk in target practice (the Nevada survived atomic bomb testing, but was sunk later).
- The Iowa-class, the newest battleships built, were decommissioned last with the Missouri not being decommissioned by the time the Korean War erupted. The war re-activated the rest of the Iowa-class from mothballs. They would be decommissioned again in the 1950s, with the USS New Jersey serving again during Vietnam. All 4 would be reactivated in the 1980s and serve until the early 1990s, with the USS Missouri and USS Wisconsin participating in the Persian Gulf War.
- The Iowa-class is another example of what could happen. While awaiting disposal, some battleships were preserved by museum groups. All 4 Iowa-class battleships are now museums, as are many WW2 battleships like the USS Alabama
The US aircraft carrier fleet followed a similar path. The importance of the carrier meant that the *Essex-*class wasn't retired rapidly, and instead became the core capital ship.
- The oldest/pre-war aircraft carriers, like the USS Enterprise, were decommissioned after the war and then sold for scrapping (a damn shame, if I may interject my personal opinion on this one)
- The *Independence-*class light aircraft carriers were largely decommissioned and eventually scrapped. Three carriers were sold/transferred to other nations - the USS Belleau Wood and USS Langley were transferred to France and put into service there, and the USS Cabot served with Spain.
- Obsolete aircraft carriers, like the escort carriers, were rapidly decommissioned with a few remaining on as aircraft transports. Likewise, heavily damaged aircraft carriers like the USS Franklin never saw post-war service again (and neither did the USS Bunker Hill). Costly repairs and modernizations were skipped for them.
- The rest of the *Essex-*class would serve and be recommissioned in the 1950s in the wake of the Korean War. Some would be modernized for modern jet aircraft with angled carrier decks and what not. Three (the Boxer, Princeton, and Valley Forge) were converted to Landing Platform, Helicopter (LPH) amphibious assault ships.
- The Essex-class carriers were reclassified into Attack Carriers (CVA) and Anti-Submarine Carriers (CVS) and would serve until the 60s and 70s until the supercarrier replaced them. The last ship of the class to serve, the Lexington, served as a trainer carrier until 1991. Many became museums.
- The Midway-class carrier, the newest class which missed serving in WW2, would serve for many decades as well, with the USS Midway participating in Desert Storm before decommissioning. It is now a museum in San Diego.
All across the military, a similar process was used to determine what to do with equipment. Obsolete aircraft and tanks were quickly retired/scrapped. Some were sold to allied nations (the M4 Sherman saw use by Israel, for instance) and some pieces of equipment continued to serve (such as the M1 Garand rifle) until eventually replaced by new service rifles in the 1950s like the M14. And even then, the M1 Garand was given to allied nations like the Republic of Korea and Republic of China, where it served for years after.