Microstructure and mechanical properties of TiC-Fe surface gradient coating on a pure titanium substrate prepared in situ

Thermal shock behaviours of atmospheric plasma sprayed NiCrAlY/Al2O3–20%TiO2 gradient coating on Cu–Be alloy

“…Gradient transition structure can significantly reduce the difference in physical and chemical properties between the ceramic coating and metal substrate, and improve the mechanical properties of the coating. Gradient coatings have been successfully fabricated to enhance comprehensive performances of carbon steel and tool steel [4,5], stainless steel [6], Ti and Ti alloys [7,8], superalloys [9], Al alloys [10], C/C composites [11], Cu [12] and graphite substrate [13]. A significant stress gradient was caused by an increase in the ceramic thickness, resulting in the horizontal crack propagation in the interface during thermal shock testing of 8YSZ-Al 2 O 3 composite coatings [14].…”

Improving the Resistance to Wear and Mechanical Characteristics of Cladding Layers on Titanium and its Alloys: A Review

“…Bamboo, for example, exhibits a gradient distribution pattern, where the distribution of fiber tube bundles steadily decreases from the outside to the inside of the cross-section, resulting in significant toughness and hardness [98]. Researchers have used this unique design concept of FGMs for surface modification of components, resulting in controlled production of gradient design claddings, which are non-homogeneous structure coatings with a progressive change in chemical composition or microstructure, leading to a gradient shift in mechanical properties [17][18][19][99][100]. The interface in the substrate-coating system is critical to material performance and operational life.…”

“…In addition, the phase composition of the coating exhibits a gradient shift from the coating surface to the substrate, and the volume percentage of the reinforcement progressively declines (or increases) from the coating surface to the substrate. For example, Bai et al [19] created cladding of pure titanium with a TiC-Fe gradient design using a two-step in-situ reaction approach. The volume percentage and grain size of TiC particles raise as they move from the coated surface to the substrate, and their shape shifts from columnar to equiaxed crystals.…”

“…However, a gain in wear property and hardness is frequently followed by a large drop in toughness, indicating that toughness and hardness have a clear "inverse connection" [15,16]. Inspire by the "inverse relationship" between the toughness and resistance to wear (hardness) of the cladding on the surface of titanium alloy, researchers have produced some innovative structural resistant-towear cladding with higher toughness and higher hardness, like gradient design cladding [17][18][19], multiscale design cladding [20][21][22], and layered design resistant-to-wear cladding [23][24][25]. Gradient-designed claddings can reduce thermal stress brought on by fluctuations in the thermal properties of various phases within the coating as well as stress between the base and cladding resulting from abrupt changes in physical properties.…”

“…Gradient-designed claddings can reduce thermal stress brought on by fluctuations in the thermal properties of various phases within the coating as well as stress between the base and cladding resulting from abrupt changes in physical properties. The load transfer effect, toughness, and hardness are improved by altering the microstructure gradient in the direction of coating thickness [19]. Multi-functional response and coupling mechanisms between reinforcements of various sizes (micron, submicron, and nano), morphologies (whiskers, particles), and phases are largely employed to increase the coating's toughness, resistance to wear, and hardness [22,26].…”