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我厂生产的汽轮机主汽门的15Cr11MoV钢阀杆、阀碟等零件,氮化后要求 HV≥650,渗层深度≥0.30mm,脆性≤3级。原采用普通氮化:530±10℃×20h,氨分解率25～30%;600±10℃×37h,氨分解率50～60%。这种钢表面极易氧化,形成致密的钝化膜 Cr_2O_3,普通氮化不仅费时(57h),而且渗层厚薄不均,甚至出现凹凸现象,造成返工。后来,我们采用电解气相催渗氮化,工艺见图1。电解液配方为工业用 HCl20%+H_2O80%+工业用 NaCl 200g/l,电解槽容积为氮化罐容积的1/100,电解电流为9～11A,N_2载体气流量为0.2M~3/h。这种工艺不仅渗氮快,由一般两段氮化57小时,缩短为24小时,而且渗层均匀,表面很少出现化合物层,渗层深达0.4mm左右,表面
I produced the steam turbine main steam valve 15Cr11MoV steel stems, valve discs and other parts, after nitriding requirements HV ≥ 650, infiltration depth ≥ 0.30mm, brittle ≤ 3 level. The original use of ordinary nitriding: 530 ± 10 ℃ × 20h, ammonia decomposition rate of 25 to 30%; 600 ± 10 ℃ × 37h, ammonia decomposition rate of 50 to 60%. This steel surface easily oxidized, the formation of dense passivation film Cr_2O_3, ordinary nitriding is not only time-consuming (57h), and the uneven thickness of infiltration layer, and even the phenomenon of bump, resulting in rework. Later, we use electrolysis gas nitriding nitriding process shown in Figure 1. Electrolyte formulation for the industrial use of HCl 20% + H_2O80% + industrial NaCl 200g / l, the volume of the tank for the nitriding tank volume 1/100, the electrolysis current of 9 ~ 11A, N_2 carrier gas flow of 0.2M ~ 3 / h . This process is not only nitriding fast, by the general two-stage nitriding 57 hours, shortened to 24 hours, and the diffusion layer evenly, the surface is rarely compound layer, the depth of about 0.4mm, the surface