Ion nitrocarburizing compound layer phase adjustment and control method for SDC 99 steel

Abstract

The invention discloses an ion nitrocarburizing compound layer phase adjustment and control method for SDC 99 steel. The nitrocarburizing temperature ranges from 520 DEG C to 540 DEG C, the flow of NH3 ranges from 550 mL / min to 620 mL / min, the equation that NH3:CO2=16:1 is satisfied, and the furnace pressure ranges from 450 Pa to 500 Pa. Argon bombardment is performed on the surface layer of a compound of the SDC 99 steel with nitrocarburizing finished for nitrogen removal, the nitrogen removal temperature ranges from 490 DEG C to 510 DEG C, and the argon bombardment time ranges from 4 hours to 7 hours. By the adoption of the method, the brittleness of a nitrocarburizing layer is further reduced, the abrasion resistance of a material surface is improved, compound layer phase adjustment and control are performed after ion nitrocarburizing is finished, and a compound layer phase mainly comprises Fe4N after nitrogen removal treatment; under the condition of a phase adjustment and control process, the thickness of a white bright layer is reduced by 4 micrometers to 5 micrometers compared with that of the white bright layer before nitrogen removal, and the thickness of the total nitrocarburizing layer is increased by 40 micrometers; and the hardness and the gradient of a section are more smooth after nitrogen removal treatment, the brittleness of a compound layer is remarkably reduced, abrasion resistance is remarkably improved, and the service life of the SDC 99 steel is effectively prolonged.

Description

technical field [0001] The invention relates to a surface treatment method for iron and steel materials, in particular to a surface nitriding treatment process for iron and steel workpieces, which is applied in the technical fields of material heat treatment and surface engineering. Background technique [0002] Nitriding treatment is a commonly used surface treatment method at present. A layer of iron nitride is formed on the surface of iron and steel parts during nitriding treatment. This layer of structure is called compound layer. It is white, so it is also called white bright layer. The bright white layer is ε-Fe from the surface to the inside 2-3 N phase, ε+γ′ phase, γ′-Fe 4 N-phase. Since different working conditions have different requirements for the white layer on the surface of the steel after nitriding, it is necessary to control the phase composition of the white layer through various process methods in order to obtain Fe in the compound layer. 4 The N phase...

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Problems solved by technology

[0003] At present, the phase control of the compound layer after nitriding in the literature reports is mainly to directly control the nitriding temperature and the nitrogen potential in the gas source to obtain the required surface layer phase composition (Mao Zhe, Li Jiliang. Using vacuum technology to improve nitriding performance[ J]. Thermal Processing Technology, 2010, 39(6): 141-142. Xie Fei, Yuan Junwei, Ma Baoyou, etc. Study on Phase Structure and Brittleness of W18Cr4V High Speed ​​Steel Ion Nitriding Layer[J]. Physical and Chemical Inspection, 1997, 33(12):3-6.) and the first nitriding and then denitrification method (Zhang Ziyuan, Zhang Guifang. Reduction treatment of nitriding white layer of 38CrMoAlA steel[J]. Metal Heat Treatment, 1992,17(11):44-47 .), the former did not control the phase composition of the compound layer of the infiltrated layer, and the latter bombarded the sample after nitriding with hydrogen ions, which can bombard the "white bright layer", but the use of hydrogen is more dangerous, and the bombardment result is not easy to control , and the bombardment will remove the less brittle γ′ phase together

[0004] Chinese patent CN85107162 adopts segmented nitriding and atmosphere control, and the obtained surface phase composition is a single-phase compound γ' or a pure diffusion layer without compounds, but the nitriding time is too long, and the process is not easy to control

Chinese patent CN91106880.5 and patent CN85100540 both regulate nitriding by adjusting the nitrogen potential. Patent CN1982496 obtains a compound-free layer nitriding method by adjusting the design of nitriding equipment, which is not applicable to the current general nitriding equipment, and the cost is relatively high high

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