几种火焰喷焊自熔性合金层的耐磨性能

研究了不同自熔性合金粉末火焰喷焊层的显微组织与抗磨粒磨损性能，并对其磨面形貌进行了ＳＥＭ观察分析。结果表明，在Ｎｉ６０自熔性合金中加入适量的镍包ＷＣ粉末可明显提高其喷焊层的抗磨粒磨损性能。当ＷＣ的加入量为３５％（ｗｔ）左右时，该喷焊层与６０Ｓｉ２Ｍｎ调质钢相比，相对的耐磨性可提高６倍以上。     

Investigation of process parameters influence in abrasive water jet cutting of D2 steel

In the present experimental study, abrasive water jet (AWJ) cutting tests were conducted on D2 steel by different jet impingement angles and abrasive mesh sizes. The experimental data was statistically analyzed using the simos–grey relational method and ANOVA test. In addition, the outcome of influencing cutting parameters, namely jet pressure, jet impingement angle, and abrasive mesh size on the different response parameters, namely, the jet penetration, material removal rate, taper ratio, roughness, and topography, were studied. Micro-hardness test and surface morphology analysis were employed to examine the D2 cut surfaces at different AWJ cutting conditions. The chemical element study was performed to determine the abrasive particle contamination in the AWJ kerf wall cut surfaces. The ANOVA test result indicated the jet pressure and jet impingement angle as the influencing process parameters affecting the various performance characteristics of AWJ cutting. The overall AWJ cutting performance of the D2 steel has been improved through proper identification of the optimal process parameter settings, namely jet pressure 225?MPa, abrasive mesh size #100, and jet impingement angle 70° by the simos–grey relational analysis.     

Surface integrity studies on abrasive water jet cutting of AISI D2 steel

This article investigates the 3D surface topography and 2D roughness profiles, and micrographs were analyzed in the abrasive water jet (AWJ) cutting of AISI D2 steel kerf wall cut surfaces by varying water jet pressures and jet impact angles. In 3D surface topography, roughness parameters such as Sq, Ssk, Sp, Sv, Sku, Sz, and Sa were improved by various jet impact angles with different water jet pressures. However, the roughness parameters Ssk and Sku strongly depend on the water jet pressure and jet impact angle. This is confirmed by kerf wall cut profile structures. Fine irregularities of peaks and valleys are found on the AWJ cut surfaces, as evident from 2D roughness profiles. The scanning electron microscope micrographs confirm the production of an upper zone not very much damaged and a lower striation free bottom zone, by using the jet impact angle of 70° with a water jet pressure of 200?MPa. Finally, the results indicate a jet impact angle of 70° maintaining the surface integrity of D2 steel better than normal jet impact angle of 90°. The results are useful in mating applications subjected to wear and friction. This has resulted in enhancement of the functionality of the AWJ machined D2 steel components.     

Effects of temperature on the tribological behavior of Al0.25CoCrFeNi high-entropy alloy

The tribological behavior of Al_0.25CoCrFeNi high-entropy alloy (HEA) sliding against Si₃N₄ ball was investigated from room temperature to 600 ℃. The microstructure of the alloys was characterized by simple FCC phase with 260 HV. Below 300 ℃, with increasing temperature, the wear rate increased due to high temperature softening. The wear rate remained stabilized above 300 ℃ due to the anti-wear effect of the oxidation film on the contact interface. The dominant wear mechanism of HEA changed from abrasive wear at room temperature to delamination wear at 200 ℃, then delamination wear and oxidative wear at 300 ℃ and became oxidative above 300 ℃. Moreover, the adhesive wear existed concomitantly below 300 ℃.     

平面绕流泥沙磨损试验及水轮机磨损预估

本文介绍室内平面绕流磨损试验结果和应用于真机的磨损预估，与刘家峡、葛洲坝机组实测磨损量核算结果差别不大。在此基础上对在建的小浪底机组做了估算，并提出了一些看法。     

白口铸铁的磨料磨损行为及耐磨性

通过白口铸铁的耐磨试验，观察分析材料的磨面和磨屑；研究不同性能的白口铸铁在磨料磨损时的行为机理．     

Abrasive wear behaviour of hardened high strength boron steel

Abstract

Abrasive wear in industrial applications such as mining, materials handling and agricultural machinery constitutes a large part of the total wear. Hardened high strength boron steels are known for their good wear resistance and mechanical properties, but available results in the open literature are scarce. This work aims at investigating how different quenching techniques affect the two-body abrasive wear resistance of hardened high strength boron steels. Furthermore, the wear as a function of depth in thicker hardened high strength boron steel plates has also been studied. The material characterisation has been carried out using microhardness, SEM/energy dispersive spectroscopy and three-dimensional optical surface profilometry. The results have shown that water quenched and tool quenched high strength boron steel had similar wear resistance. The main wear mechanisms appear to be microcutting combined with microfatigue. Workhardening during the abrasion process has been found to affect the abrasive wear.     

Comparison of anodised aluminium surfaces from four fabrication methods

This study presents a comparative analysis of surface characteristics and properties of anodised aluminium cylinders produced by sand casting, permanent mould casting, extrusion, and high pressure die casting. Differences in micro structure and distribution of silicon particles in the aluminium, due to the fabrication method and the silicon content in the alloy, resulted in varying thickness of the oxide layers (mean thicknesses between 7 and 19 μm) and surface topography. The oxide layer was unevenly thick for the permanent mould cast and the sand cast cylinders, resulting in a surface with higher plateaus and lower areas. This was more prominent for the sand cast surface. The oxide of the extruded cylinder was thick and even and its surface was smooth. The high pressure die cast surface had an oxide that was very thin and uneven. The surfaces displayed different results in the scratch test due to the variations in the surface structure. For the permanent mould cast and the sand cast surfaces the silicon particles present in the oxide deflected the cracks that were formed during the scratching. This resulted in smaller wear debris. The nanohardness values of the oxides had a large scattering due to the inhomogeneous nature of the oxide layers, with pores and particles. However, the highest nanohardness values were between 5000 and 6000 MPa for the four surfaces, which is significantly lower than that of sintered alumina. In the micro abrasion test the wear mechanism for all four surfaces was microcutting resulting in chippings.     

Modelling of surface evolution in abrasive jet micro-machining including particle second strikes: A level set methodology

A previous implementation of narrow band level set methodology for the modelling of the surface evolution of masked features in abrasive jet micro-machining (AJM) including the effect of mask erosive wear was extended to include the effect of particle second strikes. The model uses a ray tracing/node tracking algorithm to allow the prediction of the effect of particle ricochets from the mask edges and the sidewalls of the machined feature on the resulting surface evolution of high aspect ratio features. Using the model, for the first time, the prediction of the particle second strike effects from inclined masked features is made possible. When compared to previous models that did not account for mask wear and second strike effects, the present model significantly improved the prediction of measured masked micro-channels machined using AJM in glass. When compared to previous particle tracking computer simulations, the present model was found to have a much shorter execution time, and in some cases also showed an improved prediction. The model can be useful in predicting the feature shape in the AJM of brittle targets for aspect ratios greater than 1, and hence for the micro-fabrication of microfluidic and MEMS devices.     

Friction and wear behaviours of surface densified powder metallurgy Fe–2Cu–0.6C material

Surface rolling was employed to fabricate a densified layer on a powder metallurgy (PM) Fe–2Cu–0.6C piece. A densified surface layer with a depth of 335?μm and a surface hardness of 330?HV_0.1 was obtained, in which the lamellar spacing of pearlite and grain size of ferrite were refined. Friction and wear behaviours of the surface densified material were studied. Results indicated that friction coefficient of the rolled material decreased as the load increased, which was lower than that of the un-rolled material. Wear volumes were lower than that of the un-rolled material, which increased as the load increased. Wear loss was caused by flake spalling and grooves, and the wear mechanism mainly was abrasive wear. The surface densified layer with higher hardness and lower porosity can hinder the cracks initiation and propagation on the surface and under the surface, which enhance the wear resistance of the PM material.