Mechanism of multi-layer composite coatings in the zinc process of recycling coated WC-Co cemented-carbide scrap

Abstract

The mechanism of a coating is crucial for the zinc-process parameters and zinc-recycled WC powders as well as the subsequent production. The mechanism of a multi-layer composite coating in a zinc process was discussed and the coating with recycled WC powders was studied. The results demonstrated that the coating created a barrier in the zinc process, resulting in a longer recycling time for the coated hard-metal scrap. Furthermore, cracks that appeared due to different thermal-expansion coefficients of the materials were the main reason for the breakdown of the coating, rather than the reaction or the dissolution; and the molten zinc mainly went through cracks. Additionally, the coating elements and fragments were found in the recycled WC powders. Keywords: zinc process, coated cemented-carbide scrap, recycle, cracks Na~in in vrsta opla{~enja WC-Co karbidne trdine je klju~nega pomena za procesne parametre cinkanja za s cinkom reciklirane WC-prahove, kot tudi za njihovo nadaljnjo obdelavo. V pri~ujo~i raziskavi so avtorji raziskovali vpliv opla{~enja karbidne trdine na proces cinkanja za recikla`o WC-prahov. Rezultati so pokazali, da ve~slojna prevleka ustvari oviro v procesu cinkanja, kar posledi~no podalj{a~as recikliranja opla{~enih karbidnih trdin. Poleg tega so glavni razlog za pokanje prevlek razli~ni koeficienti toplotnega raztezanja materialov in namesto njihovega raztapljanja poteka infiltracija raztaljenega cinka skozi razpoke do karbidne trdine. Tako so v recikliranem WC prahu na{li tudi elemente in delce trdih prevlek.

Oxidation Behavior of Multilayer Hard Coatings (TiCN/Al2O3/TiN) in Process of Recycling Coated Multicomponent Hardmetal Scrap

“…Thus, Al 2 O 3 is defeated in recycled hardmetals, resulting in decreased adhesion strength in the interface of WC/Co, thus leading to poor performance in the recycled hardmetal. Moreover, the Al 2 O 3 coating can also be left in Zn and repeatedly influence the recycled products [ 10 ]. On the other hand, the recycling of hardmetal scraps has been considered primarily based on hydrometallurgy [ 11 ].…”