Abstract

The quality of metal powder composition (MPC) made of heat resistant alloy EP648 (Ni–Cr–W–Mo) used for fabrication of parts by direct metal deposition (DMD technology) has been analyzed. It has been established that, regarding the main requirements (chemical composition, particle size distribution, purity, bulk density, yield, moisture content), the MPC meets the requirements of Technical Specifications TU 136-225-2019. The influence of the parameters of direct laser deposition (power of laser radiation, cladding speed) on the structure and microhardness of experimental specimens has been analyzed. The highest number of defects (multiple shrinkage cavities and incomplete fusion) is formed in the specimen fabricated at the power of laser radiation P = 1000 W and the cladding speed v = 40 mm/s. At the same time, the defects have the maximum dimensions. The minimum number of defects is observed in the specimens fabricated at P = 1400 and 1600 W and v = 45 and 38 mm/s. In this case, the most homogeneous structure of laser cladding is formed owing to complete fusion of powder particles and melt spreading. Nevertheless, the structure of the specimen deposited at P = 1600 W and v = 38 mm/s contains cracks located at the subgrain boundaries in the center of cladding tracks. Their formation is caused by overheating of the metal due to higher power of laser radiation and accumulation of high internal stresses after previously deposited layers. The microhardness of the specimens fabricated by all modes of direct laser deposition changes insignificantly in the range of 270–310 HV. On the basis of the obtained experimental results, it has been determined that the most optimum structure is formed in the specimen at the laser power of 1400 W and the cladding speed of 45 mm/s.

中文翻译：

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激光直接沉积对Ni-Cr-W-Mo耐热镍合金组织和性能的影响

摘要

已经分析了用于通过直接金属沉积（DMD技术）制造零件的耐热合金EP648（Ni-Cr-W-Mo）制成的金属粉末成分（MPC）的质量。已经确定，关于主要要求（化学成分、粒度分布、纯度、堆积密度、产量、水分含量），MPC 符合技术规范 TU 136-225-2019 的要求。分析了直接激光沉积参数（激光辐射功率、熔覆速度）对实验试样组织和显微硬度的影响。在激光辐射功率P = 1000 W 和熔覆速度v下制造的试样中形成的缺陷数量最多（多个缩孔和不完全熔合）= 40 毫米/秒。同时，缺陷具有最大尺寸。在P = 1400 和 1600 W 和v = 45 和 38 mm/s下制造的试样中观察到的缺陷数量最少。在这种情况下，由于粉末颗粒的完全融合和熔体扩散，形成了最均匀的激光熔覆结构。然而，在P = 1600 W 和v= 38 mm/s 包含位于覆层轨道中心的亚晶界处的裂纹。它们的形成是由于较高功率的激光辐射和先前沉积层后高内应力的积累导致金属过热。由所有直接激光沉积模式制造的试样的显微硬度在 270-310 HV 范围内变化不大。根据所获得的实验结果，确定了在激光功率为 1400 W 和熔覆速度为 45 mm/s 时试样中形成的最佳结构。