喷丸对H13钢等离子渗氮处理的影响

Influence of shot-peening on plasma nitriding of H13 steel

对经1020℃淬火560℃、610℃和560℃三次回火后的H13钢进行喷丸处理,将喷丸处理后的试样在550℃下等离子渗氮1h。采用光学显微镜、透射电子显微镜、显微硬度仪和X射线衍射仪观察和分析,对比了喷丸和未喷丸试样亚表层的显微结构,等离子渗氮后的渗层深度、截面硬度及表面物相组成。结果表明,在550℃渗氮1h的情况下,喷丸的催渗效果十分明显,喷丸后渗氮层深度从30·4μm增至51·4μm,喷丸形成的高密度胞状位错对催渗起了决定性的作用。喷丸试样的渗氮层与未喷丸试样相比,表面物相的含量不同,表面硬度较高,渗层的硬度梯度稍平缓一些。

The H13 steel was quenched and tempered （austenitized at 1020 ℃ and tempered at 560 ℃ ,610 ℃ and 560 ℃ ） and prepared by the shot-peening. The H13 samples with or without shot-peening were plasma nitrided at 550 ℃ for 1 h. The thickness, hardness gradient and the phase contents of the nitride layers were compared between the shot-peened samples and the original samples using optical microscope, Vickers microhardness tester and X-ray diffractometer. The surface microstructure features of the samples with or without shot-peening were characterized by transmission electron microscope. Results show that the previous shot-peening greatly speeds up the nitriding on the H13 steel at 550 ℃ for 1 h. The shot-peening enhances nitride layer to 51.4 μm rather than 30. 4 μm for the sample without shotpeening. The high-density dislocation resulted from shot-peening markedly promotes the nitriding process. The phase contents of the nitride layers between the shot-peened and original samples are different. The surface hardness of shot-peened samples after nitriding is higher than that of original samples and the hardness gradient is slightly smoother.