## 1 Introduction  
The variety of cutting tools used in industry need to fulfill high requirements for hardness, toughness, wear resistance and exposure to elevated temperatures. High-speed steels (HSSs) meet all these requirements since they exhibit high hardness, bending strength and grindability [1]. These steels are Fe-C type with additions of Cr, W, Mo, V and Co, while they can be quenched with air cooling from austenization temperature. Their applications apart from cutting tools are forging and punching dies, injection molds, automotive components and space vehicles [2]. HSSs are characterized by high wear resistance and good mechanical properties due to the occurrence of a specific microstructure, i.e., a matrix of martensite and residual austenite with a grid of eutectic carbides uniformly distributed in interdendritic regions [3]. The presence of vanadium carbides, for example, is crucial from the point of view of the proper grindability of the produced tools [4]. In contrast, the increased content of cobalt in HSS results in the growth of resistance to loss of hardness at elevated temperatures and prevents cold cracking [5]. The majority of the cutting tools that need to meet increased strength criteria are made from HSS-Co steels, which are nowadays being produced through powder metallurgy (PM). The established manufacturing process for PM steels is complex and includes powder production, hot isostatic pressing (HIP), and forging followed by heat treatment with hardening and triple tempering [6]. This metallurgical process allows for obtaining a finer grid of carbides that also improves grindability [4]. High-alloy tool steels such as HSS-Co PM are considered non-weldable and prone to fracture. Therefore, processing them with additive manufacturing(AM) technologies is still a challenge because of their low repeatability [1]. The use of AM to repair a tool can lead to an anisotropy of the resultative microstructure and cause different properties of the deposited structure in relation to the substrate [7]. Another issue in developing AM technology is the accumulation of expansion and contraction stresses caused by the deposition of successive layers of additional material [8]. Among many AM techniques for processing metal alloys, one can distinguish two widely used groups of technologies: direct energy deposition (DED) and powder bed fusion (PBF) [9; 10]. Comparing the DED technique with PBF, it can be claimed that DED is characterized by a lower dimensional and shape accuracy but higher material deposition efficiency [11]. Although PBF usually permits obtaining better component properties, in some cases, DED allows achieving better mechanical properties and easier gradation by varying material composition [12]. Laser metal deposition (LMD) is a specific type of DED technology that can be used in the production, modification and reconditioning of machine parts, especially those with complex and expensive manufacturing processes that have to meet high requirements regarding abrasion, wear and corrosion resistance on surfaces exposed to wear and harsh conditions [9; 13]. The use of a laser beam as a heat source is associated with a lower amount of heat introduced into the material and, therefore, a smaller size of the melt pool and heat-affected zone (HAZ) [11]. Moreover, when the majority of conventional welding processes are characterized by cooling rates of 10-100 K/s, at laser material processing, the cooling rates are in the range of even 1000-10,000 K/s [14]. Some significant advantages can be achieved in the LMD by feeding additional material coaxially to the laser beam, i.e., independence of material deposition from the direction of laser head movement as well as the ease of supplying the shielding gas. Admittedly, there is a possibility of using the additional material in both powder and wire form. The wire gives the possibility of achieving 100% melting efficiency and higher volumetric deposition rates [15], whereas coaxial powder feeding is much more common.