Yes, in this poem, Blake’s tone is ironic that has disguised his revolutionary enthusiasm. In one part of the poem, his tone is exuberant as he describes the boy’s dream and lines are slightly rhymed as:
And by came an angel who had a bright key,
And he opened the coffins and set them all free;
Then down a green plain leaping, laughing, they run,
And wash in a river, and shine in the sun.
He then develops exuberance into a wistful tone in the following lines:
And the angel told Tom, if he’d be a good boy,
He’d have God for his father, and never want joy.
Despite that, here we see a little use of irony, which might look absurd at first however, later they do not further look absurd when readers understand the idea. For instance, in reality the boys, “locked in coffins of black,” because they clean sooty dark chimneys in “clothes of death.” Then an angel rescues them by opening their coffins with “a bright key,” and sets “all free.” Here he means that children are dead but angel releases their souls. Hence, Blake rages at cruel treatment of humans with innocent children.