13Cr4Mo4Ni4VA钢复合化学热处理过程渗层组织性能演变

摘要

Duplex thermochemical processing of 13Cr4Mo4Ni4VA steel was carried out, which involves carburizing (followed by hardening and tempering) and then nitriding. Optical microscope (OM), Scanning electron microscope (SEM), X-ray diffraction, eleciron probe micro-analyzer ( EPMA), and microhardness tester were used to investigate the evolution of microstructures and properties during the duplex thermochemical processing of 13Cr4Mo4Ni4VA steel. The results indicate that the carbon and nitrogen introduced into 13Cr4Mo4Ni4VA steel create different zones of microstructures, cause the solubility gradient of carbon and nitrogen, and bring out different hardness fields from the surface to the core, different zones in hardened layer are responded differently during each step of duplex thermochemical processing, so the variable evolution law of microstructures and properties are followed. It is greatly different from traditional case hardening, such as carburizing, nitriding, carbonitriding and nitro-carburizing. Duplex thermochemicai processing of 13Cr4Mo4Ni4VA steel leads to superior surface hardness ( ＞ 70HRC), deeper case depth, excellent case structure with double layers,and high bearing capacity.%对13Cr4Mo4Ni4VA钢进行了表层复合化学热处理,即在渗碳硬化层的基础上再进行渗氮处理,形成复合硬化层.采用光学显微镜(OM)、扫描电镜(SEM)、X射线衍射(XRD)、电子探针(EMPA)及显微硬度梯度测试等方法对复合化学热处理过程组织性能的演变规律进行探索研究.结果表明,13Cr4Mo4Ni4VA钢在复合化学热处理过程中,碳氮原子吸收和扩散使表层的碳氮浓度梯度分布,从而导致从表面到心部组织性能梯度变化,呈现不同的界面层;在不同热处理阶段,不同的界面层热处理响应不同,导致渗层不同组织、硬度分布和演变.碳氮复合化学热处理工艺和以往的单一渗碳、渗氮以及氮碳或碳氮共渗有本质区别,其不仅使表面硬度达到超硬化(>70HRC),而且渗层深,具有优异的梯度结构,承载能力强.