Effect of Substrate Type on Deposition Behavior and Wear Performance of Ni-Coated Graphite/Al Composite Coatings Deposited by Cold Spraying

This work focused on the deposition characteristics and wear behavior of Ni-coated graphite mixed with40 vol.% Al(Ni-Gr/Al) composite coatings sprayed on an Al alloy and a steel substrate by cold spraying(CS). The morphology of the ?attened Ni-Gr particles was examined by single-impact tests. Crosssectional microstructure and wear performance of the Ni-Gr/Al composite coatings were studied. Results showed that a larger number of Ni-Gr particles were ?nally bonded with the steel substrate, whereas many craters existed on the Al alloy substrate after the single-impact tests. The coating on the steel substrate had a high thickness, high graphite content and low coe?cient of friction(COF) compared to those on the Al alloy substrate. In addition, the CS coatings presented a homogeneous distribution and uniform morphology of graphite, and a comparative COF to that of conventional thermal sprayed coatings. It was shown that CS could avoid the decomposition and transformation of graphite phase.

Wear Performance and Corrosion Behavior of Nano-SiCp-Reinforced AlSi7Mg Composite Prepared by Selective Laser Melting

It is one of the future trends to create materials in situ by laser additive manufacturing. AlSi7Mg/nano-SiCp composites were successfully in situ prepared by selective laser melting in our previous study. After adding 2 wt% nano-SiC particles, the tensile stress and strain increased to 502.94 ± 6.40 MPa and 10.64 ± 1.06%, respectively. For the first time in the present study, we systematically studied and compared the wear performance and corrosion behavior of AlSi7Mg with its composite. We conducted the ball-on-fl at frictional wear test at room temperature, potentiodynamic polarization, electrochemical impedance spectroscopy(EIS), and the immersion corrosion tests in 3.5 wt% NaCl solution. The results showed that composite had higher wear resistance, while AlSi7Mg was more resistant to pitting corrosion. However, the further pitting corrosion of composite was restrained because of the in situ phase nano-Al4C3 and the residual nano-SiCp.

Abrasive Wear Characteristics of Carbon and Low Alloy Steels for Better Performance of Farm Implements

The low stress abrasion behaviours of heat treated mild, medium carbon and high C - low Cr steels, which are generally used in making farm implements, have been investigated. The simple heat treatment greatly improves the hardness, tensile strength and abrasion resistance of medium carbon and high C - low Cr steels. The results indicate that the material removal during abrasion is controlled by a number of factors, such as hardness, chemical composition, microstructure and heat treatment conditions. The conclusion is that the heat treated high C - low Cr steel and mild steel carburized by using coaltar pitch provide the best hardness and abrasion resistance and thus appear to be the most suitable materials for making agricultural tools.

Friction and wear properties of AlCrN coating by cathodic arc ion plating

AlCrN coating was prepared on the surface of TiC-based cermet cutting tool with cathodic arc ion plating,and the surface-interface morphologies,compositions of chemical elements,and phases were analyzed by scanning electron microscope(SEM),energy dispersive spectrometer(EDS),and X-ray diffraction(XRD),respectively.Bonding strength of the coating-substrate interface was measured with scratching test,and the wear mechanism and friction coefficient of TiC-based cermet cutting tool and AlCrN coating were investigated with friction and wear testing machine.The results show that the interface binding of AlCrN coating is metallurgical mode,and its binding strength is 83 N.The average friction coefficient of TiC-based cermet cutting tool under the load of 6 N is 0.8409,while that under the load of 8 N decreases by about 11%,and the wear mechanism of TiC cermet cutting tool is fatigue wear,abrasive wear,and oxidation wear.The average friction coefficient of AlCrN coating is 0.6363 under the load of 6 N,and the change is relatively stable,decreasing by about 25%than that of TiC-based cermet cutting tool;when the load increases to 8 N,the average friction coefficient of AlCrN coating decreases by 9%.The wear mechanism of AlCrN coating is abrasive wear and oxidation wear,showing lower friction coefficient and good wear resistance.

Effect of Heat Treatment on the Wear Properties of Selective Laser Melted Ti–6Al–4V Alloy Under Different Loads

As is well known,titanium alloy precipitates when subjected to aging treatment,which poses great influence on its mechanical properties.Thus,solution and solution-aging treatments were conducted in this work,and the wear performance was investigated under diff erent normal loads.The results showed that acicularα′martensite in the original selective laser melted Ti–6 Al–4 V was decomposed intoα+βphases after the solution treatment,and then Ti;Al nanoparticles clusters were further formed in theα-matrix after the solution-aging treatment.The coefficient of friction decreased straightly as the normal load was increased from 20 to 100 N,and the wear mechanisms were characterized by abrasion,adhesive and oxidative wears.The wear rate of solution and solution-aging treated samples increased significantly comparing to the as-built counterpart,but the increment of the solution-aging treated sample was smaller than that of the solution-only treated sample,because of the Ti;Al precipitation in the solution-aging treated sample.These particles provided ball-like effect,reduced material losses and stabilized the wear process.All these factors contributed to the improvement in wear properties of the parts made by selective laser melting.