金属增材制造成形液压滑阀阀芯磨损机理研究

Selective laser melting (SLM) is one type of the metal additive manufacturing technology, which provides a new way to produce and design hydraulic valves. SLM technology is based on a laser beam melting a deposited metal powder layer. The SLM parts are built by a layer-by-layer manner. Since the materials underwent through repeated and severe heating/cooling cycles, SLM parts have different micro-structures compared to conventional parts, which also changes the tribological performance. Wear on the valve spool directly influences the gap between the spool and the valve body (or the valve sleeve) affecting the reliability of the valve. The wear becomes more severe as the hydraulic valve is developing towards high speed and high pressure. Therefore, it is urgent to carry out studies on the wear mechanisms of valve spools produced by SLM in order to verify the reliability of the technology. The proposal is aimed at studying the wear mechanisms of parts produced through repeated and severe heating/cooling cycles under the reciprocating and particle erosion conditions. The project will investigate the micro-deformation behaviors of the SLM parts, the effect of surface pores and the resulted wear types under various lubrication regimes, and the relations among processing parameters, material structures, and wear mechanisms. Based on cross-disciplines of hydraulic transmission, laser processing, and tribology, the wear mechanisms of SLM-made valve spools will be discussed. Thereby, the wear resistance of valve spools can be controlled by laser processing, which further establishes the foundation for applying SLM technology to fabricate hydraulic components.

作为金属增材制造方式之一，选区激光熔化（SLM）技术为液压阀的创新设计提供了一种全新的途径。然而由于SLM是以激光逐层熔化金属粉末进行堆叠的方式成形，材料经历反复剧烈的加热/冷却循环，呈现出不同于传统材料的组织特征，并改变了材料的磨损行为。滑阀阀芯的磨损直接影响滑阀副的配合间隙，对滑阀可靠性产生重要影响。随着液压阀朝着高速、高压的方向发展，其磨损问题将更加显著，因此亟需对SLM成形滑阀阀芯磨损机理展开研究，验证SLM技术应用的可靠性。本项目针对快速剧烈熔凝成形材料在往复运动及粒子冲蚀下的磨损机理这一科学问题，从微观尺度阐明SLM成形材料的变形机制，明确表面孔隙在不同润滑状态下的作用及磨损形式，建立工艺参数、材料结构和磨损机理三者的关系。在液压传动、激光加工、摩擦学等学科交叉的基础上，揭示SLM成形滑阀阀芯磨损机理，实现对滑阀阀芯耐磨性的工艺调控，为SLM技术在液压元件领域的应用奠定基础。

激光粉末床熔融作为一种金属增材制造技术，为液压阀的创新设计提供了一种全新的途径。然而由于SLM是以激光逐层熔化金属粉末进行堆叠的方式成形，材料经历反复剧烈的加热/冷却循环，呈现出不同于传统材料的组织特征，并改变了材料的磨损行为。滑阀阀芯的磨损直接影响滑阀副的配合间隙，对滑阀可靠性产生重要影响。随着液压阀朝着高速、高压的方向发展，其磨损问题将更加显著。本项目通过研究激光粉末床熔融成形材料表面孔隙分布规律及其对不同润滑条件下的影响机制，揭示了工艺参数-表面孔隙-润滑三者间的作用机理，同时对空蚀磨损也进行了研究，揭示了工艺参数-微观结构-空蚀性能之间的关系，最后通过调控微观组织结构达到提高耐磨性的目的。研究结果表明，表面孔隙率在一定接触条件下可以加强局部二次润滑，减小摩擦系数。然而该状态十分不稳定，随着工况变化润滑状态也会随之改变，同时孔隙在摩擦力的作用下会发生闭合。较多的孔隙不仅降低成形件性能同时还会加剧磨损。对空蚀磨损而言，柱状晶由于有一定程度的变形能力，其抵抗空蚀磨损的能力强于胞状晶。在滑动接触下，将运动方向施加于平行于柱状晶短轴方向，此时外力与滑移面垂直，抗磨损能力最强。另外，晶粒取向决定滑移面的方向。通过控制热流可以在微观调整晶粒取向从事提高抗磨能力。