A powder injection nozzle for a laser cladding system, including: an elongate hollow cylindrical body, the body having a proximal end, a distal end, and a gas inlet; an elongate hollow cylindrical tube; characterized in that the tube has a constant cross-sectional outer diameter along its length; wherein the length of the body is less than the length of the tube; and in that a plug insert is arranged at the distal end of the body, the plug insert being releasably arranged between the body and the tube, wherein the plug insert has one or more openings which define a gas outlet through which a gas can be delivered from the body; a closure member is sealingly arranged at a proximal end of the body, the closure member being releasably arranged between the body and the tube so as to prevent gas from escaping via the proximal end of the body; wherein the plug insert has a central opening and the closure member has a central opening, and wherein the tube is configured to pass through the central opening of the plug insert and the central opening of the closure member such that the tube has an interference fit, or a size-for-size fit, with the plug insert and the closure member, thereby to provide a releasable sliding connection between the tube and both the plug insert and the closure member, wherein the tube can be fitted or removed from the central openings of both the plug insert and the closure member via the sliding connection; wherein the tube defines a through passage having an inlet for receiving a cladding material and a nozzle tip defining an outlet of the tube for delivering the cladding material from the tube; wherein the tube is fitted within the body, via the interference fit or the size-for-size fit with the plug insert and the closure member, such that a distal end of the tube projects forward of the distal end of the body to define the nozzle tip; wherein the tube is fitted within the body, via the interference fit or the size-for-size fit with the plug insert and the closure member, such that a proximal end of the tube extends rearwardly of the body, wherein the extent to which the nozzle tip projects forward of the distal end of the body is less than the extent to which the proximal end of the tube extends rearwardly of the body; and wherein the body, the tube, the plug insert and the closure member are all formed of the same material. an elongate hollow cylindrical body, the body having a proximal end, a distal end, and a gas inlet; an elongate hollow cylindrical tube; characterized in that the tube has a constant cross-sectional outer diameter along its length; wherein the length of the body is less than the length of the tube; and in that a plug insert is arranged at the distal end of the body, the plug insert being releasably arranged between the body and the tube, wherein the plug insert has one or more openings which define a gas outlet through which a gas can be delivered from the body; a closure member is sealingly arranged at a proximal end of the body, the closure member being releasably arranged between the body and the tube so as to prevent gas from escaping via the proximal end of the body; wherein the plug insert has a central opening and the closure member has a central opening, and wherein the tube is configured to pass through the central opening of the plug insert and the central opening of the closure member such that the tube has an interference fit, or a size-for-size fit, with the plug insert and the closure member, thereby to provide a releasable sliding connection between the tube and both the plug insert and the closure member, wherein the tube can be fitted or removed from the central openings of both the plug insert and the closure member via the sliding connection; wherein the tube defines a through passage having an inlet for receiving a cladding material and a nozzle tip defining an outlet of the tube for delivering the cladding material from the tube; wherein the tube is fitted within the body, via the interference fit or the size-for-size fit with the plug insert and the closure member, such that a distal end of the tube projects forward of the distal end of the body to define the nozzle tip; wherein the tube is fitted within the body, via the interference fit or the size-for-size fit with the plug insert and the closure member, such that a proximal end of the tube extends rearwardly of the body, wherein the extent to which the nozzle tip projects forward of the distal end of the body is less than the extent to which the proximal end of the tube extends rearwardly of the body; and wherein the body, the tube, the plug insert and the closure member are all formed of the same material.