This article presents the Laser Beam Direct Energy Deposition (DED-LB) process as a method to build a graded austenitic-to-martensitic steel junction.

Builds were obtained by varying the ratio of the two powders during DED-LB processing. Samples with gradual transitions were successfully obtained using a high dilution rate from one layer to the next. Long austenitic grains are observed on the 316 L side while martensitic grains are observed on the Fe–9Cr–1Mo side. In the transition zone the microstructure is mainly martensitic.

Characterisations performed after building and after a tempering heat treatment at 630 °C for 8 h were compared to dissimilar Electron Beam (EB) welds. Before heat treatment the DED-LB graded area has high hardness (values of around 430 HV) due to fresh martensite formed during building. Tempering heat treatment reduces this hardness to 300 HV.

EDS measurements indicate that the chemical gradient between 316 L and Fe–9Cr–1Mo obtained by DED-LB is smoother than the chemical change obtained in EB welds. Microstructures in DED-LB are quite different from those obtained by EB welding. Hardness values in DED-LB samples and in welds are similar; the weld metal and the Fe–9Cr–1Mo heat-affected zone are relatively hard after welding because of fresh martensite, as found in the DED-LB transition zone; both are softened by tempering heat treatment.

Tensile tests show that DED-LB samples and EB welds have similar behaviour with failure in 316 L base metal at 20 °C and 400 °C and failure in Fe–9Cr–1Mo base metal at 550 °C. DED-LB samples have comparable mechanical properties to EB welds.

本文介绍了激光束直接能量沉积 (DED-LB) 工艺作为一种构建渐变奥氏体-马氏体钢结的方法。

通过在 DED-LB 加工过程中改变两种粉末的比例来获得构建。使用从一层到下一层的高稀释率，成功地获得了逐渐转变的样品。在 316 L 侧观察到长奥氏体晶粒，而在 Fe-9Cr-1Mo 侧观察到马氏体晶粒。在过渡区，显微组织主要是马氏体。

将成型后和在 630 °C 下回火热处理 8 小时后进行的表征与不同的电子束 (EB) 焊缝进行比较。在热处理之前，DED-LB 分级区域具有高硬度（大约 430 HV 的值），因为在构建过程中形成了新鲜的马氏体。回火热处理将该硬度降低到 300 HV。

EDS 测量表明，通过 DED-LB 获得的 316 L 和 Fe-9Cr-1Mo 之间的化学梯度比在 EB 焊缝中获得的化学变化更平滑。DED-LB 中的显微组织与通过 EB 焊接获得的显微组织有很大不同。DED-LB 样品和焊缝中的硬度值相似；焊后由于新鲜马氏体，焊缝金属和 Fe-9Cr-1Mo 热影响区相对较硬，如 DED-LB 过渡区；两者均通过回火热处理软化。

拉伸试验表明，DED-LB 样品和 EB 焊缝具有相似的行为，316 L 母材在 20 °C 和 400 °C 下失效，Fe-9Cr-1Mo 母材在 550 °C 下失效。DED-LB 样品具有与 EB 焊缝相当的机械性能。