Abstract: The present invention relates to steel alloys having a martensitic or martensitic-ferritic structure and comprising Z-phase (CrXN) particles, where X is one or more of the elements V, Nb, Ta, and where the Z-phase particles have an average size of less than 400 nm. The alloy comprises by wt % the following components: 9 to 15% Cr, 0.01-0.20% N, C in an amount less than 0.1%, one or more of: 0.01-0.5% V, 0.01-1% Nb, 0.01-2% Ta, and a balance being substantially iron and inevitable impurities. The invention further relates to a method of manufacturing such a steel alloy, a component comprising such a steel alloy, and to the use of such a steel alloy for high temperature components.