Abstract: A cold spray apparatus is provided that includes a nozzle having a converging section and a diverging terminal section. A gas supply meters a majority by atomic percent helium gas to the nozzle at an incident gas temperature of less than 30° Celsius and at an incident velocity of between 2 and 6 MPa. A particulate feeder provides ductile material particulate having a mean x-y-z axially averaged linear dimension of between 0.9 and 95 microns to the nozzle. A composition is also provided that includes a substrate and a coating of ductile metal. The coating has a void density of less than 1% by volume, and an average domain size of between 0.9 and 95 microns. The coating has a compressive residual stress.