Laser alloying technology has found extensive application in preparing wear and corrosion resistant Ti6Al4V surfaces, attributed to its high production efficiency and robust coating strength. Nevertheless, the current technology mandates a secondary finishing operation on the strengthened surface, leading to a convoluted process and substantial energy consumption. Hence, this research endeavors to integrate the laser alloying of the Ti6Al4V surface with the grinding process, thereby conducting a titanium alloy surface machining-strengthening integration via laser alloying grinding. Specifically, it focuses on preparing separable B4C coatings for the boron-carbon strengthening of Ti6Al4V surfaces based on laser alloying grinding. Comparative experiments are carried out to explore the distinct advantages of laser alloying grinding in aspects such as dynamic grinding force, surface morphology, surface microstructure, and comprehensive surface properties. The combined influences of laser softening, multi-abrasive cutting, and second-phase dispersion strengthening on the machined surface quality are analyzed. During laser alloying grinding, the residual laser energy can heat the remelted layer in the grinding contact area up to 350 ℃. This high temperature softens the remelted layer, effectively curbing the increase in grinding force and ensuring a more stable grinding process. In laser alloying grinding, the softening of the material lessens the indentation depth of the abrasive grits, which remarkably reduces the groove depth and the bump height on the machined surface. The surface roughness Sa of the machined surface after laser alloying grinding is approximately 2.2 µm, representing a 30% reduction compared with that of conventional grinding (Group 2). Subsequent to laser alloying grinding, a remelted layer forms on the Ti6Al4V surface covered with a B4C coating. This remelted layer comprises a dense granular or dendritic matrix phase (α-Ti and β-Ti), with uniformly distributed carbide and boride phases in its interstices. The grain size within the remelted layer is notably smaller than that of conventionally ground surfaces. The dispersion strengthening effect of carbides and borides significantly enhances the comprehensive mechanical properties of the remelted layer. The microhardness of the remelted layer reaches 710HV, which is twice that of the matrix Ti6Al4V. The elastic modulus of the remelted layer shows a slight increase. Simultaneously, the adhesive wear of the remelted layer is suppressed, and the wear resistance is markedly improved, with the wear size being merely 30% of that of the substrate. Additionally, the boride phase exhibits excellent chemical stability. After laser alloying grinding, the dense remelted layer effectively impedes the direct contact of the corrosive medium with the Ti6Al4V matrix. The self-corrosion current density (Jcorr) of the machined surface is only one-third that of the matrix phase. The polarization resistance of the laser-alloyed grinding surfaces increases substantially. In conclusion, laser alloying grinding represents a novel study in the synergistic processing of Ti6Al4V surface properties and accuracy through boron-carbon precipitation. It improves surface characteristics such as microstructure distribution, hardness, wear resistance, and corrosion resistance, and can serve as a guiding reference for surface anti-fatigue manufacturing.
Key words
laser alloying grinding /
Ti6Al4V /
B4C coating /
property-accuracy synergistic
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Funding
Quzhou City Science and Technology Plan Project (2024K200); Quzhou University Doctoral Startup Fund (BSYJ202216)
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