WordNet records no synonym and no antonym for powder metallurgy. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the metallurgy of powdered metals; how to produce solid metal objects from powdered metal by compaction and sintering
Synonyms, antonyms and the broader and narrower relations for powder metallurgy come from Princeton University’s WordNet. Full sources and licences.