I am on mobile so forgive the poor formatting. It is known that the Mongol cavalry carried a spear/lance, which would have been sufficient to pierce plate armor in a cavalry charge to levels of lethality. (Citation 1) Another source (Citation 2) indicates that the Mongols carried maces, which in general were used against heavily armored opponents. Maces have the ability to pierce plate armor to levels of lethality.
Also, I found a similar question with a similar topic (See Citation 3, which is a link to another /r/ AskHistorians thread) concerning the armor piercing qualities of the Mongol arrow (and bow). One of the users responded with a reply stating that the Mongols might not have fought against knights or soldiers wearing full plate armor, only partial plate and mail armor. It is hard to say whether the Mongol bow and arrow had enough power to penetrate strong plate armor, and a search shows that this is still up for debate (some modern tests show that piercing is possible, but might not be at a level be completely lethal).
Citation 3 - https://m.reddit.com/r/AskHistorians/comments/3hj8h5/did_any_of_the_mongolian_horse_archers_ever_get/