Liujie Xu

Microstructure and Wear Resistance of Fe-Cr-C Hardfacing Alloy Reinforced by Titanium Carbonitride

In order to improve the wear resistance of Fe-Cr-C hardfacing alloy, titanium carbonitride was introduced in situ and a TiC-Tix(C,N)y coating was deposited on the surface of ASTM G3101 steel by a gas metal arc welding process. The microstructure and wear resistance of the hardfacing layer were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDS), macroscopic hardness meter, spectrometry, and transmission electron microscopy (TEM). The results show that the hardfacing layers mainly consist of (Cr,Fe)7C3, TiC carbides, Tix(C,N)y carbonitrides, and α-Fe (C0.14Fe1.86 and C0.12Fe1.88 martensite) (BCT) in addition to a low content of retained CFe15.1 austenite (FCC). The titanium carbonitride–reinforced coating has high hardness and excellent wear resistance under dry sliding wear test conditions.

Microstructure and High-Temperature Frictional Wear Property of Mo-Based Composites Reinforced by Aluminum and Lanthanum Oxides

In this article, we developed Mo-based composites reinforced with aluminum and lanthanum oxides using a sol-gel method combined with a sintering process and researched the microstructure and frictional wear properties under high-temperature conditions. The microstructure of composites was characterized by α-Al2O3 and composite oxide (La0.62Mo0.38)AlO3, which were uniformly distributed in the molybdenum matrix. The composite oxide (La0.62Mo0.38)AlO3 was mainly attached to α-Al2O3. The interfaces of α-Al2O3/Mo and α-Al2O3/(La0.62Mo0.38)AlO3 were well bonded. The α-Al2O3 refined the molybdenum grains, increased the relative density and hardness of Mo-based composites, and had an obvious effect on the frictional wear properties of the composites. With increasing α-Al2O3 content, the friction coefficient first increased and then decreased, and the wear weight loss decreased continuously. The wear failure mode varied from microcutting to fatigue with increasing α-Al2O3 content. The better wear resistance of Mo-based composites, compared to pure molybdenum, was mainly attributed to the characteristics of α-Al2O3, such as high microhardness, good morphology, well-bonded phase interface, and high hardness matrix due to the effects of α-Al2O3 reinforcement.

Effect of Carbides on Wear Characterization of High-Alloy Steels under High-Stress Rolling–Sliding Condition

This article describes the wear characterizations of high-speed steel composed of vanadium carbide and high-chromium cast iron composed of chromium carbide. These metals were studied under rolling–sliding conditions with a sliding ratio of 10% using a self-made ring–ring wear testing machine. The fine microstructure of carbides and failure behaviors were analyzed by scanning electron microscopy and high-resolution electron microscopy. The results showed that carbide significantly affected the wear properties and failure behaviors of metals. The relative wear resistance of high-speed steel reinforced by vanadium carbides was twice that of high chromium cast iron composed of chromium carbides. Chromium carbide was characterized by a stacking fault substructure, and slips occurred in chromium carbide under high-stress contact, resulting in crack formation. Vanadium carbide was reinforced and pinned by large amounts of nanoparticles, which prevented its dislocation under high-stress rolling–sliding conditions, thereby effectively resisting crack initiation. Furthermore, the (200) lattice plane of vanadium carbide is coherent with the (111) lattice plane of austenite, preventing cracks from forming at the interface of the vanadium–carbide matrix. The morphology and hardness of vanadium carbide also contributed to the excellent wear property of high-speed steel.