Many business dictionaries state that there is no difference between the terms work in process and work in progress, so you should generally not have trouble interchanging the terms.
However, there is a difference based on the common usage of the terms process and progress. "Process" implies that there is a manufacturing process in place where products are created under a standardized and ongoing production system. Thus, work in process applies more readily to a manufacturing environment.
The word "progress" implies a longer-term period during which a product is completed, possibly covering a number of accounting periods. Given the implied duration, this means that work in progress more readily applies to longer-term consulting projects and construction projects. In both cases, there is no highly engineered process in place for arriving at a final product, as would be the case in a manufacturing environment.
These concepts do not apply to construction projects, for which there is a separate construction-in-progress account that accumulates costs. Once a construction project has been completed, the balance in this account is shifted into a fixed assets building account.
In short, there are differences in how you can use the terms work in process and work in progress - however, these are fine distinctions, so you should be able to use either term in most cases.