This study focuses on surface treatment of aluminium alloys by High Speed Steel (HSS30) via Plasma Transferred Arc. The main motivation of this research has been an assignment of local company in order to prolong the lifetime of a tire press molds, especially the interface of its segments. These segmented molds are made from aluminium alloy and their interface is exposed to multiple percussions, which leads to cracks. Therefore, PTA surfacing is considered as a suitable surface treatment for hardening its interface, yet benefit from lightweight of aluminium matrix. For purposes of this research AlSi9CuNiMn alloy was used as a matrix metal. Permeation in the contact zone was examined via confocal and scanning electron microscope. Hardness of affected matrix area was measured by using Vickers Hardness Tester.