氮-甲醇保护气氛对45CrNiMoVA高强钢氢致断裂的影响

采用化学成分分析、断口形貌分析、显微组织分析、力学性能测试等方法对断裂后的45CrNiMoVA钢制高强扭杆进行了分析,并开展了氮-甲醇保护气氛下零件表面氢含量的测定,探讨了氢致缺陷对高强钢零件扭转疲劳的影响机理,提出了防止渗氢的预防措施,并进行了试验验证。结果表明,在氮-甲醇保护气氛下进行高强钢加热可导致氢的侵入,产生氢脆现象,影响高强钢零件扭转疲劳寿命。将氮-甲醇可控气氛更改为氮气保护,配合花键部位人工涂刷防脱碳涂料可有效防止表面氧化脱碳。采用改进工艺,高强钢扭杆未发生断裂现象。

Effect of nitrogen-methanol atmosphere on hydrogen-induced fracture of 45 CrNiMoVA high strength steel

A fractured high-strength torsion bar made of 45CrNiMoVA steel was analyzed by means of chemical composition analysis, fracture morphology analysis, microstructure analysis and mechanical property tests. The hydrogen content on the surface of the parts under nitrogen methanol protective atmosphere was measured, and the influence mechanism of hydrogen induced defects on torsion fatigue of the high-strength steel parts was discussed. The preventive measures to prevent hydrogen permeation were put forward and verified by experiments. The results show that the heating of high strength steel in nitrogen-methanol protective atmosphere can lead to hydrogen invasion and hydrogen embrittlement, which affects the torsional fatigue life of high strength steel parts. The surface oxidation decarburization can be effectively prevented by changing the nitrogen-methanol controlled atmosphere to nitrogen protection and applying the anti-decarburization coating on the spline parts artificially. No fracture occurs in the high-strength steel torsion bars by the improved processes.