If it is a stainless steel part, which would make a good deal of sense in a residential washing machine environment for corrosion resistance it is almost certainly austinitic SS which is not hardenable, 303,304, 308 or 316 alloys for instance. Martensitic alloys, 410, 416, 440 for example can be hardened but will never achieve the RC hardness of a tool steel, so have at it.
Manufacturing residential appliances is a very competitive business, the added cost of making parts from say 410 or 17-4 SS then rough machining followed by heat treatment then finish machining would be prohibitive for the most part, unless the component demands such processing it would not be done.