President Vladimir Putin’s promise to boost arms spending should have been a boon for this hardscrabble factory town, famed for making the heavy tanks that destroyed Nazi panzers in World War II. But such hopes are wearing thin for welders like Denis Morozov, who makes the same wage he did four years ago—$550 a month. Even with overtime, it is just enough to keep up his aging Russian-made four-door Lada and a pack-a-day cigarette habit, he says. …