Preparation and toughening mechanism of Mo₂NiB₂‐based cermets with SiC whiskers

Abstract

Mo2NiB2 is a kind of cermet with excellent mechanical properties, stable chemical properties, and excellent corrosion resistance and is often used in wear‐resistant application fields, such as injection molding machine parts, can making tools and hot copper extruding dies. The brittleness of Mo2NiB2‐based cermets limits their wide application. Mo2NiB2‐based cermets were prepared by the vacuum sintering method, the effect of SiC whiskers (SiCw) on the microstructure and mechanical properties of cermets was investigated, and the toughening mechanism of SiCw on cermets was further discussed. The results indicate that with increasing SiCw content, the indentation fracture toughness (KIC), transverse fracture strength (TRS), and Vickers hardness (HV) of the cermets first increase and then decrease. The HV, TRS, and indentation fracture toughness of Mo2NiB2‐based cermets with 0.5 wt% SiCw are 1 113 HV, 1 620 MPa, and 27.97 MPa·m1/2, respectively, which are 16.8%, 22.7%, and 25% higher than those without SiCw. In the sliding friction tests, Mo2NiB2‐based cermets with 0.5 wt% SiCw have the smallest friction coefficient, low wear rate, and high wear resistance. SEM observation and analysis of the crack path and fracture surface showed that the toughening mechanism is whisker bridging, crack deflection, microcrack toughening, and whisker pull‐out. The results indicate that the addition of 0.5 wt% SiCw can effectively improve the mechanical properties of Mo2NiB2‐based cermets and further expand the application space of Mo2NiB2‐based cermets.

High damage tolerant Al2O3 composite ceramics constructed with short Al2O3 fibers

“…Lots of effort has been made to alleviate the brittle failure of ceramic materials. Such as phase change toughening, [3][4][5] particle dispersion toughening, 6,7 whisker toughening, [8][9][10] long fiber toughening, 11,12 and bionic structure toughening 2,13,14 developed to overcome the sensitivity to defect. Among them, the long fiber toughening and bionic structure composite ceramics achieve the optimal nonbrittle failure manner with high toughness and work of fracture together with considerable strength.…”