Study On The Structure And Properties Of Plasma Nitriding Of 20CrMnTi Steel By Rare Earth Immersion

In this paper,the effect of rare earth solution soaking pretreatment on the structure and properties of plasma nitriding of 20CrMnTi steel is studied,and a new rare earth accelerating technology is developed.In this paper,the samples were pretreated with rare earth solution and then nitrided at different temperatures.The microstructure and properties of the layer were characterized by metallographic microscope,SEM and EDS,XRD,microhardness tester,electrochemical workstation and friction and wear tester.The surface morphology and energy spectrum of the sample after soaking and nitriding were shown.After soaking in the rare earth solution,the rare earth elements can adhere to the surface of 20CrMnTi steel and form a uniform distribution.After nitriding treatment,certain concentrations of rare earth can be detected on the surface of nitriding samples and in the nitriding layer.In conclusion,the addition of rare earth in plasma nitriding process can be realized by soaking the sample in rare earth solution.The nitriding was carried out by soaking the rare earth solution,and the infiltration layer was still composed of the white layer and the diffusion layer.The appropriate concentration of rare earth solution can increase the thickness of the white layer.After soaking in the rare earth solution,the nitriding layer was composed of?-F_2-3N???-Fe₄N and?_N at different temperatures.When nitriding was performed at 460?,Ce immersion treatment of rare earth solution increased the concentration of??-Fe₄N in the permeable layer,and Ce of rare earth solution had little effect on the phase structure of the permeable layer.With the same concentration of rare earth solution,increasing the nitriding temperature promoted the formation of?-F_2-3N phase and??-Fe₄N phase in the surface layer.The hardness distribution and thickness of the ooze layer will be affected by the soaking of rare earth solution nitriding:when the solution concentration of rare earth La solution is 0.5%and 1%when the ooze layer is soaked at 460?,the hardness distribution of the ooze layer is higher than that of the unsoaked nitriding sample.Other concentrations have little effect on the distribution of the ooze layer and even reduce the ooze layer hardness.When the concentration of rare earth solution containing La was 0.5%and the nitridation was 460?,the thickness of the permeable layer increased most significantly,from 231?m to265?m,and the thickness of the permeable layer increased by 27.4%.Nitriding treatment can significantly improve the corrosion resistance of20CrMnTi steel.When nitriding at 460?,the corrosion resistance of rare earth soaked layer decreased slightly,but it was still higher than the matrix.When nitriding at 520?and 560?,the addition of rare earth La can further improve the corrosion resistance of the infiltration layer.After the treatment of nitriding by rare earth immersion,the hardness of the nitriding layer increases to reduce the degree of wear of the abrasive particles and reduce the friction coefficient.The addition of rare earth increases the oxygen content on the surface,which is conducive to the formation of oxide film and the reduction of wear degree of abrasive particles.