The Process Research Of H13 Forging Die Plasma Nitriding

H13 is widely used as the the track link forging dies, working at a temperature over 1000℃. The average service life is about 9000 pieces, and most of them failed in abrasion damage, which causes a poor appearance and a low production efficiency. It is urgent to prolong the forging die service life.The first method we chose is to improve the matrix material, which was abandoned finally for its limited enhance. For its abrasion damage failure, the best method is to improve the wear performance, which could be achieved by plasma nitriding. The process and the influence of the process parameters on nitrated case performance were researched in this article, which offered a reliable foundation for heat treatment process of H13.The following conclusions were got through the research:(1) The hardness of the nitrated case first rises and then falls with the temperature increment. The maximum hardness value 1200HV appeared at 500℃. The thickness of the nitrated case rises with the temperature, and nearly the same at 500℃ and 520℃, which achieve an ideal hardness gradient.(2) With the extension of time, the hardness of the nitrated case falls and the depth of the case rises, while the hardness gradient tends to be stable.(3) With the increase of the pressure, the surface hardness first rises and then falls, which achieved at maximum value at 300pa. It is the same with the depth of the nitrated case.(4) All the layer is diffusion layer without compound layer. Nitride network appeared when the heating time arrives 18h, which should be avoided in production.(5) The residual stress rises with the increase of the parameters, but the compressive stress on the surface can improve the fatigue strength, which is good to the service life.(6) The service life of the nitriding forging die improved by 27%, about 2566 pieces, with a good appearance quality.