不同渗氮时间下二段式真空渗氮后PCrNi3Mo钢表层的显微组织与性能

Microstructure and Properties of PCrNi3Mo Steel Surface Layer after Two-Stage Vacuum Nitriding under Different Nitriding Time Conditions

采用二段式真空渗氮工艺对调质态PCrNi3Mo钢进行表面改性处理,在渗氮温度及氮势相同的条件下,对比研究了强渗阶段和扩散阶段时间均为6 h以及强渗阶段时间为4 h和扩散阶段时间为8 h条件下试验钢表层的组织、物相组成、硬度及耐磨性能。结果表明:渗氮后试验钢表层物相为ε-FeN相,2种渗氮时间下渗氮层的厚度分别为0.6,0.7 mm左右,表面硬度分别为660.3,581.3 HV,显著高于基体的360 HV;前者渗氮时间下渗氮层中化合物层致密性较差,微孔较多,渗氮层硬度过渡良好,在距表面距离大于0.3 mm时的硬度较高,渗氮层的摩擦因数和磨损量较低,磨损表面犁沟较浅,耐磨性能较好。

Two-stage vacuum nitriding process was used to modify the surface of quenched and tempered PCrNi3Mo steel. Under the condition of the same nitriding temperature and nitrogen potential, the microstructure, phase composition, hardness and wear resistance of the surface layer of the test steel were studied under the conditions of strong infiltration for 6 h and diffusion for 6 h, and compared with those by strong infiltration for 4 h and diffusion for 8 h. The results show that after nitriding, the phase of the test steel surface layer was ε-FeN phase. Under two nitriding time conditions, the thickness of nitrided layer was about 0.6, 0.7 mm, and the surface hardness was 660.3, 581.3 HV, respectively, higher than 360 HV of substrate. Under the former nitriding time condition, the compound layer in the nitriding layer had poor compactness and a great number of micropores;the hardness transition of the nitriding layer was good, and the hardness was relatively high at the distance from the surface of greater than 0.3 mm;the friction coefficient and wear amount of the nitrided layer were relatively low, and the furrow on the wear surface was shallow, indicating the wear resistance was relatively good.