不同表面热处理H13钢与7075铝合金板高温摩擦实验对比研究

Comparative Study on High-Temperature Friction Behavior of Differently Surface-Treated H13 Steel Die and 7075 Aluminum Alloy Sheets

  • 摘要: 在热冲压过程中,铝合金板材与H13钢之间的滑动接触常导致严重磨损与粘着转移,这会显著降低成形质量并缩短模具寿命。本研究基于自主研发的板带式高温摩擦试验机,根据铝合金板材热冲压工艺模拟了固溶-成形-淬火过程,研究了加热的7075铝合金薄板与H13钢模具之间的摩擦学性能。研究了在不同法向载荷下,分析三种表面处理状态下H13钢模具与7075铝合金高温摩擦行为及机理。具体三种表面处理如下:(I)淬火和回火(Q&T);(II)Q&T后离子渗氮(PN);(III)Q&T 后PVD-TiN 涂层(PVD-TiN)。实验结果表明,法向压力增大时,摩擦系数升高,粘着磨损加剧;在不同压力条件下,PVD-TiN涂层与渗氮涂层均展现出优异的减摩性能。在4.5MPa中等压力条件下,尽管PVD-TiN 模具的摩擦系数低于渗氮表面改性模具,但由于 PVD-TiN 涂层较薄易发生局部剥落,使新鲜金属表面暴露,其粘着磨损比渗氮表面改性模具更严重;而渗氮处理形成的 Fe?N、Fe?N 等化合物可有效抑制粘着现象。在 5.4MPa 高压力条件下,PVD-TiN 表面改性模具不仅能保持较低的摩擦系数,其表面形成的 TiN 颗粒还可显著减轻粘着磨损,性能优于渗氮表面改性模具;而渗氮表面改性模具在高压力下会因塑性变形产生 Fe-Cr 合金团状颗粒,导致摩擦副接触状态恶化。

     

    Abstract: The sliding contact between aluminum alloy sheet and H13 steel in hot stamping often?leads to severe wear and adhesive transfer, significantly degrading forming quality and tooling life.?This study simulates the actual solution-forming-quenching process of hot stamping on a self-developed sheet-and-strip high-temperature friction tester. This study reveals the influence of different normal pressures on the thermal tribological behavior between three types of surface-modified H13 steel, quenched and tempered (Q&T) H13 steel, Q&T H13 steel combined with ion plasma nitriding (PN), and Q&T H13 steel combined with PVD-TiN coating (PVD-TiN)) and high-temperature aluminum alloy. The experimental results reveal that increased normal pressure a higher friction coefficient and intensified adhesive wear. Both PVD-TiN coating and nitriding coating exhibit excellent friction-reducing performance under different pressure conditions. Under the medium pressure condition of 4.5Mpa, although the friction coefficient of the PVD-TiN surface modified tool is lower than that of the surface nitrided tool, the adhesive wear is more severe than that of the surface nitrided tool because the thinner coating is prone to local spalling, exposing the fresh metal surface. However, the compounds such as Fe?N and Fe?N formed by nitriding treatment can effectively inhibit adhesion. Under the high pressure condition of 5.4Mpa, the the PVD-TiN surface modified tool not only maintains a lower friction coefficient, but also the TiN particles formed on its surface can significantly reduce adhesive wear, showing better performance than the surface nitrided tool. The latter, however, deteriorates the contact condition of the friction pair due to the formation of Fe-Cr alloy aggregate particles caused by plastic deformation.

     

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