HSS coating with keyholes in penetration produced by laser cladding process

Abstract

This paper is devoted to the assurance of higher durability of hard coatings by using irregular method of laser cladding (LC). The purpose of this study was to demonstrate that by producing of keyhole mode LC coatings enables to create functionally graded structure in interface. This can contribute to decrease the gradient of trough-depth residual stresses of the coating-substrate system formed by dissimilar steels. Experimental work was carried out using precise LC system, which consists of industrial robot (KUKA) and 1kW Yb-fiber laser (IPG Laser). Experimental coatings were created on cold work tool steel substrate AISI D2 using high-speed steel (HSS) powder AISI M2. The properties of coatings produced by two different methods have been evaluated in the course of a comparative analysis by examination of morphology of transverse cross-sections, elemental composition, microhardness distribution inside coatings and tribological tests. Results showed that coating with keyhole mode in penetration had lower hardness due to a larger amount of dilution however the smooth transition of properties in the interface was obtained. Despite the significant difference in hardness both coatings demonstrated very similar tribological behaviour.