Effect of wetting on the incorporation behavior of powder particles in laser melt injection at high processing speed

尽管激光熔体注射在生产功能部件表面方面具有明显的技术优势，但由于工艺速度低和相关的生产率低，该工艺尚未在工业中得到广泛接受。然而，目前的研究表明，高速注入熔体是可行的。而且，此时该工艺仅限于使用润湿性好的金属硬质材料，而氧化物颗粒由于润湿性差而无法加工。因此，该项目的总体目标是更好地了解高工艺速度下激光熔体注射的过程。这种理解应该能够在最大工艺速度、高工艺速度下可实现的硬颗粒含量以及使用氧化物颗粒的可行性方面扩展当前工艺限制。特别是，该项目旨在了解激光熔体注射过程中粉末颗粒在熔池中的掺入行为。低速过程和高速过程之间的差异需要加以识别。粉末颗粒的掺入行为与基体熔体对硬质材料的润湿性、颗粒与基体熔体的密度比以及粉末颗粒的动能等输入因素有关。通过确定主要影响参数，应开发高速激光熔体注射工艺，该工艺仍允许加入高硬颗粒含量。为了提高硬质材料的润湿性，首次在激光熔融注射中研究了钛包覆硬质颗粒。特别是，这将使氧化硬材料在激光熔体注射中的使用成为可能。此外，改善的润湿性应确保即使在非常高的工艺速度下也有足够的颗粒融入熔池，以实现MMC涂层中的高硬颗粒含量。

Although laser melt injection offers clear technological advantages over other processes for producing functional component surfaces, this process has not yet been widely accepted in industry due to low process speeds and the associated low productivity. Current investigations however indicate that high speed melt injection can be feasible. Moreover, at this point the process is limited to the use of metallic hard materials with good wettability, while oxide particles cannot be processed due to poor wettability. Therefore, the overall goal of the project is to better understand the process of laser melt injection at high process speeds. This understanding should enable an extension of the current process limits in terms of maximal process speed, achievable hard particle content at high process speed, and also in terms of feasibility of using oxide particles.In particular, the project aims to generate an understanding of the incorporation behavior of powder particles in the melt pool during laser melt injection. Differences between a process at low speed and a process at high speed are to be identified. The incorporation behavior of powder particles is to be correlated with the input factors wettability of the hard materials by the substrate melt, density ratio of particles and substrate melt and kinetic energy of the powder particles. Through identification of the main influencing parameters, a high speed laser melt injection process shall be developed that still allows for the incorporation of a high hard particle content. To improve the wettability of the hard materials, titanium coated hard particles shall be investigated for the first time in laser melt injection. In particular, this should enable the use of oxidic hard materials in laser melt injection. In addition, the improved wettability should ensure that sufficient particles incorporate into the melt pool even at very high process speeds in order to achieve a high hard particle content in the MMC coatings.