A track link for a track in a ground-engaging machine comprising: an elongate link body including a first link body end and a second link body end , and having a lower shoe-mounting surface , an upper rail surface , a first inner surface defining a first track pin bore adjacent to the first link body end , and a second inner surface defining a second track pin bore adjacent to the second link body end ; the elongate link body being formed of a link body material that varies in hardness within the elongate link body to form a first lower hardness zone , a second lower hardness zone , and a higher hardness zone ; the first lower hardness zone including the first inner surface and extending circumferentially around the first track pin bore , the second lower hardness zone including the second inner surface and extending circumferentially around the second track pin bore ; and the higher hardness zone including at least a majority of the upper rail surface and extending throughout the elongate link body outside of the first lower hardness zone and the second lower hardness zone , wherein the elongate link body further includes a third inner surface and a fourth inner surface forming a first bolting window and a second bolting window , respectively, located longitudinally between the first track pin bore and the second track pin bore , and a strut extending between the first bolting window and the second bolting window ; the first lower hardness zone includes a portion of the third inner surface , and the second lower hardness zone includes a portion of the fourth inner surface ; the track link being characterised in that the higher hardness zone includes the strut . an elongate link body including a first link body end and a second link body end , and having a lower shoe-mounting surface , an upper rail surface , a first inner surface defining a first track pin bore adjacent to the first link body end , and a second inner surface defining a second track pin bore adjacent to the second link body end ; the elongate link body being formed of a link body material that varies in hardness within the elongate link body to form a first lower hardness zone , a second lower hardness zone , and a higher hardness zone ; the first lower hardness zone including the first inner surface and extending circumferentially around the first track pin bore , the second lower hardness zone including the second inner surface and extending circumferentially around the second track pin bore ; and the higher hardness zone including at least a majority of the upper rail surface and extending throughout the elongate link body outside of the first lower hardness zone and the second lower hardness zone , wherein the elongate link body further includes a third inner surface and a fourth inner surface forming a first bolting window and a second bolting window , respectively, located longitudinally between the first track pin bore and the second track pin bore , and a strut extending between the first bolting window and the second bolting window ; the first lower hardness zone includes a portion of the third inner surface , and the second lower hardness zone includes a portion of the fourth inner surface ; the track link being characterised in that the higher hardness zone includes the strut . <EOS>