The paper deals with the structure features of Fe-C alloys quenched by means of laser, electron beam and plasma arc. The martensite and residual austenite obtained are highly inhomogeneous. Their morphology and distribution depend both on the initial state before quenching and on the kinetics of the temperature changes. Four different structures of martensite are observed – package, lamellar isothermal, lamellar thermo-kinetic and “feathery nest-like”. The new martensite structure observed, called by us “feathery nest-like”, is a result of explosive austenite-martensite transformation in pearlitic irons. It differs from the classic modification in its specific morphology. Low-carbon package martensite occupies the regions of the former ferrite grains. Its hardness reaches 1050-1150 HV0.1. In the regions of microstructure with increased carbon concentration lamellar martensite is observed. The residual austenite is with different proportion in relation to the martensite. In particular regions its quantity could reach 100%. It is characterized by a high quantity of imperfections and high mechanical properties. Its hardness reaches 450-500 HV0.1. The higher the power density and the lower the energy density of the concentrated energy flux, the higher the residual austenite quantity.