No, Matthew 18:18 does not expand on Matthew 16:18-19. The two passages are quite distinct and no keys are mentioned in Matthew 18:18. Since it is the power of the keys that you've attempted to say all of the apostles exercised you have yet to make a case for that proposition because Matthew 18:18 does not help your claim. Matthew 16:18-19 confers the keys on saint Peter and no one else.
Saint Augustine calls the keys, “
the keys of binding and loosing.”
http://www.ccel.org/ccel/schaff/npnf104.v.iv.vi.i.html?highlight=keys#highlight
If, then, Matt. 16 connects the keys with the power to bind and loose, why should it be necessary to repeat the word “keys” in Matt. 18 when the same power, already connected to the keys, is in view?
Again, Saint Augustine connected the keys of Matt. 16 to the power of binding and loosing also mentioned in Matt. 18 when he wrote that our Lord “has given, therefore, the
keys to His Church, that whatsoever it should
bind on earth might be bound in heaven, and whatsoever it should
loose on earth might be loosed in heaven.”
http://www.ccel.org/ccel/augustine/doctrine.xviii.html?highlight=keys#highlight
Saint Jerome wrote, "But you say, the Church was founded upon Peter: although elsewhere the same is attributed to
all the Apostles, and they all
receive the keys of the kingdom of heaven, and the strength of the Church depends upon them all alike."
Against Jovinianus,1 (A.D. 393), in NPNF2,VI:366 (acknowledgement to RC apologist Dave Armstrong for this quote)
The early, sainted pope again: “
This power of the keys is translated to all Apostles and bishops.” Leo I (d. 461), quoted in Harold Browne’s An Exposition of the Thirty-Nine Articles, 1854, pp. 809,810)
Anselm wrote, “It is to be noted that
this power was not given to Peter only, but as Peter answered one for all, so in Peter he gave this power to all.”
https://archive.org/stream/a547284200beveuoft#page/n603/mode/2up
The Lateran Council of 1215, considered an ecumenical council by the RCC, states that Jesus Christ Himself gave “the
keys of the Church,” not to Peter alone, but “to the Apostles and their successors.”
http://legacy.fordham.edu/halsall/basis/lateran4.asp
The famous doctor of the church, Thomas Aquinas, posed the question, “Whether the key is the power of binding and loosing, etc.?” In this section Aquinas responded to the specific objection, “It would seem that the key is not the power of binding and loosing.” Aquinas reasoned, however, that “
the same power whereby a priest…
can loose and bind” [Matt. 16 & 18]
is “the power of the keys.”
http://www.newadvent.org/summa/5017.htm
Again, Aquinas answered the question, “Whether the priest can bind through the power of the keys?” Aquinas then affirmed that “the operation of
the priest in
using the keys, is conformed to God's operation.” Aquinas went on to say that the priest uses the keys in absolving, binding, and loosing. Thus Aquinas also connected the keys promised to Peter with binding and loosing (Matt. 16 & 18).
http://www.ccel.org/ccel/aquinas/summa.XP_Q18_A3.html?highlight=keys#highlight
Aquinas also addressed the question, “Whether priests alone have the keys?” as though the fact that priests also have the keys was a settled belief, not a matter of dispute as in this thread. Aquinas quoted Saint Ambrose: “Ambrose says (De Poenit. i): ‘This right,’ viz. of binding and loosing, ‘is granted to priests alone.’” Aquinas added, “By receiving
the power of the keys, a man is set up between the people and God. But this
belongs to the priest alone.”
http://www.ccel.org/ccel/aquinas/summa.XP_Q19_A3.html
The RC Council of Trent decreed that “in accordance with
the power of the keys, [priests] may pronounce the sentence of forgiveness or retention of sins,” thus connecting the keys promised to Peter individually with the power bestowed on all the Apostles to forgive or retain sins (John 20).
http://www.thecounciloftrent.com/ch14.htm
The traditional, catholic, patristic, and mediaeval view was thus articulated by Theophylact: “For though it be said to Peter only, ‘
I will give to thee,’ yet
the same power was given to all the apostles, when he said, ‘
Whose soever sins ye remit shall be remitted’” Theophylact on Matt. 16, quoted in Ecclesia Anglicana, Ecclesia Catholica: or, The Doctrine of the Church of England… by William Beveridge pp. 585-586)
https://archive.org/stream/a547284200beveuoft#page/n601/mode/2up