Yes, Melville's Redburn has been the topic of many dissertations in the past and certainly works. However, it is not really possible to simply outline a dissertation project without researching it first. What you should do is look at the dissertation abstracts (a database in your library) and see what other doctoral candidates have written in the past. Since a dissertation is a research project that acknowledges what is going on in a particular field and shows your take on it, you must engage with the previous material before outlining a dissertation. The dissertation outline is called a prospectus and is a summary of each chapter and a list of sources you plan to use ( the bibliography).
There are a number of topics though under which you may investigate the work. For instance people who have written about empire and American expansionism in the nineteenth century have used Redburn, but other possibilities are to look at masculinity and seafaring, notions of aesthetics, and historical readings that work comparatively (here you could compare Melville to his contemporaries). A good way to begin pinning down what interests you is by examining a good biography of Melville that discusses Redburn. Pay attention to the bibliography that the biographer uses or cites and then investigate the works that address Redburn. This will also reveal that there are periods where Melville seems to be more interesting to critics than at other times. The linked summary is a good beginning. Good luck!