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A fine-grained WC-15wt%Al0.5CoCrFeNi cemented carbide was prepared through a vacuum and gas pressure sintering. For achieving high surface integrity, diamond wheel grinding serves as the primary molding process for the machining of WC cemented carbide. To reveal the influence of grinding on the surface integrity of fine-grained WC-HEA cemented carbide, studies were conducted on grinding force, surface microstructure, surface roughness, residual stress, microhardness, and bending strength. The morphological analysis of the ground surface indicated a transition in the material removal mechanism of WC-HEA cemented carbide from ductile removal to brittle removal, with brittle removal becoming predominant as the depth of grinding increases. With the increasing depth of grinding, the grinding force increases, and the grinding force increases while the surface roughness decreases. Correspondingly, there is an improvement in both hardness and bending strength. Additionally, grinding induces high residual compressive stress on the surface, with a maximum compressive stress of 1795 MPa. The bending strength of the material is found to be dependent on the residual stress. [ABSTRACT FROM AUTHOR]

The preparation of functional coatings on metal substrates is an effective method to enhance the surface of steel structures with good serviceability in applications for engineering parts. The objective of this research is to analyze the surface properties of two sorts of medium-entropy alloy (MEA) coatings prepared by laser cladding. After cladding, the two prepared coatings were strengthened by ultrasonic burnishing (UB) treatment. Cladding coating samples before and after being UB-treated were comparatively tested in order to investigate the process effects of UB. When compared with corresponding untreated coating samples, the roughness values of the two sorts of UB-treated samples were decreased by 88.7% and 87.6%, the porosities were decreased by 63.8% and 73.4%, and the micro-hardness values were increased by 41.7% and 32.7%, respectively. Furthermore, the two sorts of UB-treated coating samples exhibited better mechanical properties and wear resistance than corresponding untreated samples. [ABSTRACT FROM AUTHOR]

Laser cladding has been commonly utilized for restoring high value-added parts. However, the poor surface quality becomes key technological barrier which restricts its widespread applications. In the paper, re-contouring strategies by machining method are explored for minimal energy consumption as well as required surface roughness. Firstly, the effect of structural characteristics of the laser-cladded workpiece on specific cutting energy was explored by means of layer-by-layer turning and orthogonal cutting. Results indicated that the specific cutting energy increased, and the machining chatter/vibration exacerbated with decreasing coating thickness under fixed cutting parameters. The reason can be summarized as a result of the effect of elastoplastic deformation behavior across the interface. Then, the influences of depth of cut and feed on specific cutting energy in finish turning were addressed. Results indicated that the specific cutting energy reduced with increasing depth of cut and feed in the form of power functions. In addition, energy efficiency decreased with an increase in uncut chip thickness and cutting speed. On basis of this work, large feed and low cutting speed with the adoption of wiper inserts were recommended for minimizing energy consumption within surface roughness requirement. [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC)-coated tools are suitable for the machining of various aluminum alloys, graphite, and other non-ferrous metals. The shortcomings of DLC-coated tools such as high internal residual stress, low toughness, and poor adhesion strength limit their application. In order to reveal the mechanical and cutting performance of DLC-coated tools, a DLC monolayer coating, Cr/CrN/DLC composite coating, and Cr/W-DLC/DLC composite coating had been prepared on the cemented carbide cutting tools. The influences of transition interlayer on the microstructure and mechanical properties of DLC coatings were analyzed. Tool lives, wear mechanism, and machined surface roughness obtained with uncoated cemented carbide tool, DLC monolayer–coated tool, and Cr/x/DLC-coated tool during the machining of Al-Si alloys were investigated. Compared with DLC monolayer coating, the strength ratio (ID/IG) of the DLC composite coatings with Cr/x transition structure was improved, while the sp3 covalent bond contents was decreased. The results show that the adhesion strength and toughness of the Cr/x/DLC composite coating were enhanced, and the residual stress was greatly reduced. The cutting tests further indicate that the DLC coating significantly improved the tool life. Based on comprehensive evaluation, the Cr/W-DLC/DLC composite coating has the highest adhesion, highest toughness, the lowest residual stress, and the longest tool life, and it is suitable for the machining of non-ferrous metal. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of turning process on surface quality and corrosion behaviors of laser cladded coatings on the 1045 steel. Corrosion resistance of the 1045 steel is improved by laser cladded Fe−Cr−Ni coatings. The as‐cladded coating behaves nobler and more resistant to corrosion compared to the 1045 steel substrate. By using turning as a finish process, surface roughness Ra of the laser cladded coating is decreased to 0.517 µm to meet the surface roughness requirement (i.e., Ra ≤ 0.8 µm) of a single‐telescopic hydraulic column. Also, surface defects including laps, cavities, and adhered material particles occur on the cladded coatings after machining. The machined coatings exhibit comparable polarization resistance compared to the as‐cladded condition, and the polarization resistance of the machined surface increases with feed rate increasing. The corrosion pits show sensitivity on feed marks induced by machining. This concentrated distribution of corrosion pits is a result of the fluctuation of local electron work function (EWF), which promotes the formation of local corrosion cells in adjacency to feed marks. [ABSTRACT FROM AUTHOR]

Saw-tooth chip changes from macroscopically continuous ribbon to separated segments with the increase of cutting speed. The aim of this study is to find the correlations between chip morphology and machined surface micro-topography at different chip serration stages encountered in high speed cutting. High strength alloy steel AerMet100 was employed in orthogonal cutting experiments to obtain chips at different serration stages and corresponding machined surfaces. The chips and machined surfaces obtained were then examined with optical microscope (OM), scanning electron microscope (SEM), and white light interferometer (WLI). The result shows that chip serration causes micro-waves on machined surface, which increases machined surface roughness. However, wave amplitudes (surface roughness) at different serration stages are different. The principal factor influencing wave amplitude is the thickness of the sawed segment (tooth) of saw-tooth chip. With cutting parameters in this study, surface roughness contributed by chip serration ranges from 0.39 μm to 1.85 μm. This may bring on serious problems in the case of trying to replace grinding with high-speed cutting in rough machining. Some suggestions have been proposed to control the chip serration-caused surface roughness in high-speed cutting based on the results of the current study. [ABSTRACT FROM AUTHOR]

Abstract: In this paper cutting experiments of AerMet100 (52 HRC) using nano TiAlN-coated carbide tools with cutting speed from 250m/min to 7000m/min are carried out. The cutting tool wear characteristics under ultra-high cutting speeds are examined and the corresponding mechanisms are analyzed. The focus is put on the tool wear characteristics and mechanisms at cutting speed above 500m/min. The influences of cutting temperature and workpiece dynamic mechanical properties on tool wear are discussed. The results show that the tool wear mechanism is highly influenced by cutting temperature and workpiece mechanical properties. At cutting speed of 500m/min the dominate wear mechanism is micro chipping and fracture due to the cutting force vibration and cold welding of contacting materials between cutting tool and workpiece. At higher cutting speed from 1000m/min to 7000m/min the predominant tool wear mechanisms are abrasion, adhesion, and fracture due oxidation, and thermal softening, and grooving by hard grains. The roughness of tool flank at this cutting stage decreases with the increase of cutting speed due to the high thermal softening. The increase of workpiece material brittleness with the increase of cutting speed lowers the elastic rebound of machined surface and reduces the tool wear rate. [Copyright &y& Elsevier]