Tip in case you haven't discovered it yet:

Don't tell them about your efficiency improvements. They won't appreciate it. You've made their job harder by requiring them to think about something. To them it was already automated and that automation was you.

Instead, just keep producing the same outputs and say nothing. You'll only get a raise or promotion when you get a new job, so spend the extra time on that. When you do get a new job, give the automation to one coworker, preferably your replacement.

Source: am experienced engineer