**3.4. Others**

In view of their comparatively high cost, titanium matrix composites are somewhat less popular than Al-based or ferrous matrix composites. Again, carbides—particularly TiC [14, 15, 33, 71, 72], but also WC [73] or SiC [74]—have attracted a great interest as reinforcement in titanium matrix composites, with positive effect on their hardness and wear behaviour. TiB, TiB2 [20, 75] and TiN [18] have also been used as alternative or in combination with TiC.

Copper (Cu) alloys are rather difficult to process by laser additive processes, due to their high reflectivity to laser light [26]. Nevertheless, the DLS of Cu matrix composites reinforced with Co/WC particles has been studied extensively, with the aim of combining the excellent thermal and electrical conductivity of the Cu matrix with the high strength and hardness of the Co/WC reinforcement [76, 77]. Rare earth oxides nanoparticles (CeO2, La2O3) have been added in these Cu + Co/WC composites to favour microstructural refinement [78]. More recently, the direct addition of WC particles in Cu matrix composites processed by SLM has also been investigated [79].

Researches on Co-based matrix composites have been largely focused on the LC of composite reinforced with WC or other cermet particles, in view of applications necessitating a very high abrasion resistance as, e.g. in cutting tools [5, 80–82]. WC present a greater reactivity with Co alloys than with Ni alloys, and the partial dissolution of WC accompanied by secondary precipitation of finely dispersed complex carbides is commonly reported. A recent publication also reports on the LC of self-lubricating Co-based composite coatings with additions of TiC and CaF2 [83].
