China
Africa
Explore chapters and articles related to this topic
Mechanical Properties
Published in Debasish Sarkar, Nanostructured Ceramics, 2018
Resistance to crack propagation under stress is “fracture toughness,” but resistance to plastic deformation or penetration by sharp object is “hardness.” While considering the penetration, the sharp indenter assisted localized stress is sufficiently high to initiate local plastic deformation from dislocations, twinning, grain boundary shear, and eventually cracking of the surface. However, this feature varies material to material. One should not be misled and select the material for structural application without enough information about the quantitative magnitude of hardness and toughness together. For example, a ductile non oxide ceramic, titanium silicon carbide (Ti3SiC2) is predominantly deformed under applied load without formation of any crack around the indenter and exhibits very low hardness (Hv = 5 GPa) and high fracture toughness (KIC = 9 MPa.m1/2) [30]. Different combination of such properties are preferentially used as structural ceramics, for example, SiC (Hv = 27.47 GPa, KIC = 3.5 MPa.m1/2), Si3N4 (Hv = 15.38 GPa, KIC = 6.89 MPa.m1/2), Al2O3 (Hv = 21.9 GPa, KIC = 4.2 MPa.m1/2), ZrO2 (Hv =13.7 GPa, KIC = 6.4 MPa.m1/2), MgAl2O4 (Hv = 18 GPa, KIC = 2.6 MPa.m1/2), etc. [31–34]. In this context, some classic discussion is emphasized to understand the basic philosophy of hardness assessment for bulk, grains, coating, and correlate with grain size and load. Eventually, this brief information may compile to design high wear resistance ceramics for load bearing applications.
A review on recent developments in binder jetting metal additive manufacturing: materials and process characteristics
Published in Powder Metallurgy, 2019
Asier Lores, Naiara Azurmendi, Iñigo Agote, Ester Zuza
Another interesting material for jet engine applications is titanium silicon carbide (Ti₃SiC₂), due to its unique ceramic-metallic behaviour that combines high mechanical resistance, thermal shock resistance, high electrical and thermal conductivity, high oxidation resistance, high machinability, low hardness and high stiffness. Lorenz et al. [88] carried out some tests combining in one hand BJ technology with Cold Isostatic Pressing (CIP), and in the other BJ with Uniaxial Pressing (UP). Then, samples from both procedures were sintered at 1600°C for 2 h and characterised. CIP-ed samples were pressed at 35, 150 and 180 MPa, and UP ones pressed under 765 MPa. Also, unpressed samples were fabricated for comparison purposes.