An artificer must use an appropriate spellcasting focus when casting artificer spells. And they must use costly material components when applicable. Neither can replace the other.
But can they handle their focus and costly material components with the same hand? I know of spells that contain more than one material component, such as Simulacrum involving both snow and powdered rubies. I am not sure whether that applies when there is both a focus and a material component in use.
Does an artificer require two hands to cast spells with a costly material component?