[時「とき」] => At the time A N5
Time
を[機「き」]に => Use A as an opportunity N1
Time, Situation
Vた[時「とき」] => After having done something N5
Time
て[以来「いらい」] => After A, B (continuous action/condition N2
Information, Report
を[契機「けいき」] => As a good opportunity A, (do) B N2
Information, Report
へ => Go to N, head to N , Often followed by verbs like 行く/いく, 来る/くる, 向かう/むかう… N5
Particles