Salaam & Greeting

Making Salaam when greeting

Q: I want to know about salaam. I heard or read in book when Nabi (Sallallahu Alayhi Wasallam) used to meet any one He use to greet him with salaam and when departing then also with salam. Is it correct if someone says Allah Haafiz or Allah ki hifazaat when departing or Sabaahul Khair? Please  give me some explanation according to Hadith.