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.