Soviet President Leonid Brezhnev flew to Moscow yesterday, expressing satisfaction with summit talks with West German Chancellor Helmut Schmidt.

But Brezhnev's four-day visit apparently failed to narrow differences over neutron weapons and Berlin.

In a joint declaration which the Soviet party leader signed Saturday with Schmidt, the two countries urged energetic efforts to promote detente and achieve progress in curbing the arms race.

They also warned that detente could suffer if efforts to reach agreement on cutting back the world's arsenals were not acclerated.

"The new thing is the complete openness of the talks on almost everything in the world . . . That is the real political result of the talks," Schmidt told a news conference here minutes after Brezhnev's Ilyushin jetliner left for Moscow.

Schmidt said President Carter planned to telephone him later for a briefing on the summit.

Brezhnev, 71, bundled in a black hat and overcoat against a chilling wind, was given a full military sendoff at Hamburg airport.

In Moscow, Brezhnev was met at Vnuvko diplomatic airport by Premier Alexei Kosygin and other top Soviet officials at a welcoming ceremony broadcast live on Soviet television.

The Soviet news agency Tass called Brezhne's visit "brilliant new page" in "the chronic of major international event."