In a large mixing bowl, combine the shredded chicken, refried beans, cheddar cheese, chili powder, cumin, garlic powder, onion powder, salt, and black pepper. Mix until well combined.
Lay a tortilla flat on a clean surface. Spoon about 1/3 cup of the chicken mixture onto the center of the tortilla. Fold in the sides and then roll it up tightly from the bottom to the top. Repeat with the remaining tortillas and filling.
In a large skillet, heat the vegetable oil over medium heat. Once hot, carefully place 2-3 chimichangas in the skillet, seam side down. Fry for about 3-4 minutes on each side, or until golden brown and crispy. Remove and drain on paper towels.
Serve hot with sour cream and salsa on the side.