Travel is more general and can involve a trip of any length. It is also general and can refer to any movement from one place to another and all such movement. "Most travel in the U.S. is by car." "He travels 30 kilometers to work." A journey always refers to a single trip, sometimes divided into smaller trips, usually with some purpose in mind. I would not say that I journey to work. "His journey took him to seven countries." "Their journey lasted for two months."