A stator, comprising: a core with an outer surface extending about a rotation axis, wherein the outer surface defines one or more surface discontinuity therein; and a coolant jacket deposited on the outer surface of the core and defining a coolant channel, wherein the coolant jacket comprises a plurality of layers (134/136) conformally disposed on the outer surface of the core and inhabiting the one or more surface discontinuity, wherein the plurality of layers (134/136) each have a radial thickness and include a first layer deposited on the outer surface of the core and circumferentially about the core, and a second layer deposited on the first layer and circumferentially about the outer surface of the core at a location radially outward of the first layer; the first layer of the plurality of layers (134/136) comprises a fused metallic particulate, the second layer of the plurality of layers comprises a fused metallic particulate, wherein the second layer is fused to the first (layer 134); wherein either or both of the fused metallic particulate and the fused metallic particulate include metallic material, including aluminium or titanium and/or alloys thereof; characterized in that:: a heat transfer structure (156/158) arranged within the coolant channel, wherein the heat transfer structure (156/158) is selected from a group including a turbulator, a riblet, and a spire; wherein the heat transfer structure (156/158) is formed from a fused particulate from the same process as the fused metallic particulate and/or the fused metallic particulate, and is spaced apart from the coolant jacket by a portion of the outer surface of the core; wherein the heat transfer structure (156/158) is defined by the outer surface of the core or defined by at least one of the plurality of layers (134/136) in the coolant channel. a core with an outer surface extending about a rotation axis, wherein the outer surface defines one or more surface discontinuity therein; and a coolant jacket deposited on the outer surface of the core and defining a coolant channel, wherein the coolant jacket comprises a plurality of layers (134/136) conformally disposed on the outer surface of the core and inhabiting the one or more surface discontinuity, wherein the plurality of layers (134/136) each have a radial thickness and include a first layer deposited on the outer surface of the core and circumferentially about the core, and a second layer deposited on the first layer and circumferentially about the outer surface of the core at a location radially outward of the first layer; the first layer of the plurality of layers (134/136) comprises a fused metallic particulate, the second layer of the plurality of layers comprises a fused metallic particulate, wherein the second layer is fused to the first (layer 134); wherein either or both of the fused metallic particulate and the fused metallic particulate include metallic material, including aluminium or titanium and/or alloys thereof; characterized in that:: a heat transfer structure (156/158) arranged within the coolant channel, wherein the heat transfer structure (156/158) is selected from a group including a turbulator, a riblet, and a spire; wherein the heat transfer structure (156/158) is formed from a fused particulate from the same process as the fused metallic particulate and/or the fused metallic particulate, and is spaced apart from the coolant jacket by a portion of the outer surface of the core; wherein the heat transfer structure (156/158) is defined by the outer surface of the core or defined by at least one of the plurality of layers (134/136) in the coolant channel. a heat transfer structure (156/158) arranged within the coolant channel, wherein the heat transfer structure (156/158) is selected from a group including a turbulator, a riblet, and a spire; wherein the heat transfer structure (156/158) is formed from a fused particulate from the same process as the fused metallic particulate and/or the fused metallic particulate, and is spaced apart from the coolant jacket by a portion of the outer surface of the core;