Microstructure and wear behaviors of a WC10%-Ni60AA cermet coating synthesized by laser-directed energy deposition

Abstract

This study successfully prepared crack-free WC10%-Ni60AA cermet coatings with high hardness using directed-energy deposition incorporating substrate preheating up to 500 °C. At the bottom of the deposit, the crack-free coating microstructure exhibited a lamination layer with a coarse herringbone eutectic, and the crystal-microstructure phase mainly comprised γ-Ni solid solution and eutectic precipitation Ni17W3, Ni31Si12, and Cr23C6. At the middle and top of the deposit, the microstructure exhibited a dense net-like eutectic, including a dendritic with the main phase of γ-Ni solid solution, interdendritic with a main phase of Cr23C6, and subdendritic with a main phase of Ni31Si12, Ni17W3, and a small block-like precipitate with a main phase of Cr2.4W0.6Si. Furthermore, the deposits on the substrate preheated to 500 °C exhibited the highest hardness (812 HV, an increase of 64 % compared to that of the non-preheating sample) owing to the dense net-like eutectic precipitation with fine-grain structure. Furthermore, wear test results show that the wearing process is divided into three stages: the rapid-increase stage; the plowing-friction stage; and the stable-wear stage. Specifically, as the load increased from 100 N to 400 N, the width and depth of the wear tracks increased, and the wear mechanisms were adhesive and oxidation, with the most severe wear occurring under a load of 400 N. Similarly, as the speed increased from 50 RPM to 300 RPM, the width and depth of the wear tracks increased, and the wear mechanisms were adhesive and oxidation at low speeds. When the speed was increased to 300 RPM, the most severe wear occurred, and the wear mechanisms were primarily adhesive and abrasive, along with a small amount of oxidation wear.