Powdered, heat-hardenable coating materials with high storage stability and a grain size smaller than 0.25 mm based upon hydroxy-group-containing polyesters with melting points between 40.degree. and 120.degree. C., blocked polyisocyanates and optionally catalysts, wherein the coating material contains polyisocyanates blocked with cyclic amidines of the general formula ##STR1## wherein R=equal or different substituents selected from the group consisting of hydrogen, alkyl-, cycloalkyl-, aralkyl-, and alkyl radicals. A method for the production of the above mentioned coating materials and a process for coating substrates with these materials is also disclosed.