Abstract

In the present study, a series of Ni + xCr₇C₃ (x is the weight fraction of the Cr₇C₃) clads on hydro turbine steel (CA6NM) were developed through microwave cladding. The weight fraction of Cr₇C₃ was 10 wt%, 20 wt%, and 30 wt% in the developed clads. These clads were developed to mitigate the erosion induced degradation of the substrate surface. The Ni + 10% Cr₇C₃ composite clad exhibited poor erosion characteristics compared to Ni-based (Ni + 0% Cr₇C₃) clad due to embrittlement of the Ni-based matrix caused by dissolution of reinforced Cr₇C₃ particles. Maximum erosion resistance was exhibited by Ni + 30% Cr₇C₃, followed by Ni + 20% Cr₇C₃ clad. The enhanced slurry erosion performance of Ni + 30% Cr₇C₃ clad can be related to increased volume fraction of Cr₇C₃ carbides and other secondary phases, such as M₇C₃, Ni₂Si. The average microhardness and fracture toughness of Ni + 30% Cr₇C₃ clad was on the order of 756 ± 37.8 HV and 12.9 ± 0.64 MPa√m, respectively. Analysis of eroded surface indicates that Ni + 30% Cr₇C₃ clad exhibited an optimum combination of hardness and fracture toughness for mitigation of slurry erosion.

摘要

在本研究中，一系列的Ni +的X的Cr ₇ C ^ ₃（X是重量分数的Cr ₇ C ^ ₃）上水力涡轮机钢（CA6NM）包层通过微波包被开发出来。在显影包层中，Cr ₇ C ₃的重量分数为10重量％，20重量％和30重量％。开发这些包层以减轻腐蚀引起的基底表面降解。在Ni + 10％的Cr ₇ C ^ ₃相比Ni基（镍+ 0％Cr的复合包层表现出较差的特性侵蚀₇ Ç ₃）是由于增强的Cr ₇ C ₃颗粒溶解而导致的Ni基基质脆化而形成的。Ni + 30％Cr ₇ C ₃表现出最大的耐蚀性，其次是Ni + 20％Cr ₇ C ₃包覆。Ni + 30％Cr ₇ C ₃包覆的增强的浆料侵蚀性能可能与Cr ₇ C ₃碳化物和其他次级相（例如M ₇ C ₃，Ni ₂ Si）的体积分数增加有关。Ni + 30％Cr ₇ C ₃的平均显微硬度和断裂韧性包层分别为756±37.8 HV和12.9±0.64MPa√m。对腐蚀表面的分析表明，Ni + 30％Cr ₇ C ₃熔覆层具有最佳的硬度和断裂韧性组合，可减轻浆液侵蚀。