Study on the detailed micro-structural characteristics of Laser Cladding in terms of porosity distribution, dilution of alloying elements and stresses in the laser melted zone using focused ion beam tomography

在过去的1-2年里，激光对表面进行了修饰。已经有一些出版物，其中不同的表面性质改性已经研究。这主要包括腐蚀、氧化、磨损、摩擦和硬度。从这些研究中获得的有用信息也有助于各种工业采用这种技术，作为一种替代方法。例如，激光硬化已被许多行业所采用，以取代传统的表面渗碳、离子渗氮和等离子渗氮。激光合金化和熔覆技术已扩展到船舶零件、曲轴和航空发动机涡轮叶片等复杂昂贵部件的修复中。我们一直在进行激光表面合金化和包覆的工作，并在表面的改性方面做出了贡献，例如钢，不锈钢，钛的腐蚀，氧化和磨损行为。详细的研究证实了表面改性是根据氧化和腐蚀机理进行的。我们还使用这种技术制造近净成形的部件，使用激光成形。然而，人们认为激光熔化区或熔覆层内部的微观机制仍然不清楚。究竟是激光处理致密化的作用，还是微观组织（非晶或微晶）的变化，以及合金元素稀释的作用，目前还不是很清楚。在我们最近的交流中，以及我在萨尔大学（Saarland University）担任功能材料教授（Prof. F. m<s:1> cklich博士）的短暂停留中，我发现了对这种研究的专门兴趣。该研究所拥有基本的激光设备，在微观结构评估方面非常强大，使用复杂的技术，如聚焦离子束断层扫描、XRD和其他表面分析工具。因此，双方建议在这一领域进行合作——我们在激光合金化和熔覆方面的专业知识以及他们在微观结构评估方面的专业知识。

Surface modifications by laser are being practiced now for the last 1-2 decades. There have been several publications, where different surface property modifications have been studied. This includes mainly, corrosion, oxidation, wear, friction and hardness. Useful information obtained from these siudies has also helped in adaption of this technique by various industries, as an alternative process. For example, laser hardening has been adopted by many industries in place of conventional case-carburizing, ion-nitriding and plasma nitriding. Laser alloying and cladding have been extended to the repair of several complicated and expensive components such as ship parts, crank shafts and aero-engine turbine blades. We have been carrying oul work on laser surface alloying and cladding and contributed towards the modification of surfaces, such as steel, stainless steels, titanium in terms of their corrosion, oxidation and wear behavior. Detailed studies confirm the surface modification as per the mechanism of oxidation and corrosion. We have also used this technique to fabricate near-net shaped components using laser forming.It is however, felt that the micro-mechanisms within the laser melted zone or cladding are still not clear. Whether it is the role of densification due to laser treatment or it is the change in microstructure (amorphous or micro-crystalline) and also the role of dilution of the alloying elements is not very clear. During our recent interactions and my short stay at the chair of functional materials (Prof. Dr. F. Mücklich) at Saarland University, I found a dedicated interest towards this kind of study. The instituie has basic laser facilities and is very strong in micro-structural evaluations using sophisticated techniques such as focused ion beam tomography and XRD and other surface analytical tools. It was therefore proposed to work together on this field - with our strong expertise in laser alloying and cladding and their strong expertise in micro-structural evaluations.