Yes. In your profile settings, you can disable the Friends feature at any time. When disabled:
Other members won't be able to send you friend requests, and you won't appear on the Friends page for others to find you.
Sending friend requests will also be disabled on your end.
Your existing friends list will remain unchanged, but you can always remove individual friends manually from your friends list.
You're always in control — you can turn this setting back on whenever you'd like.