机械能助Al-Zn-Cr共渗工艺及渗层组织

Al-Zn-Cr Diffusion Process Aided by Mechanical Energy and Microstructure of Alloying Layer

采用机械能助渗技术,在600℃温度下对20钢进行Al-Zn-Cr共渗试验。利用光学显微镜、扫描电镜(SEM)、能谱仪(EDS)等仪器,分析合金元素铬对渗层组织共渗速率的影响,分析助渗时间对渗层组织的影响,测定铬在渗层中的分布,以及铬含量对渗层厚度的影响。结果表明:在机械能助Al-Zn-Cr共渗的研究中,铬含量的增加促进了渗层厚度的增加,而铬在渗层中分布相对均匀,无富集现象。在相同助渗时间下,铬含量的增加,促进了共渗速率的提高,促使渗层组织由单一的铁铝渗层组织转变为铁铝、铁锌多层渗层组织。在同一渗剂配比条件下,助渗时间的延长,促进Fe-Zn相形成,Fe-Al相减少。在助渗条件为600℃、3 h、5%Cr时,渗层为α-Fe(富锌)、Fe_3Zn_(10)、FeZn_7、FeAl等相组成的多层组织,而且相对致密;渗层兼顾抗氧化性和阴极保护作用。

Alloy layers containing Al-Zn-Cr were obtained on 20 steel by the mechanical-energy infiltration technology at 600℃. With the aid of optical microscope, scanning electron microscopy and energy dispersive X-ray spectrometry, the influence of alloying element Cr on co-permeation rate of alloying layer, the influence of infiltration time on the microstructure of alloying layer, the distribution of Cr in the layer and the effect of Cr content on the thickness of layer were investigated. The results show that the thickness of diffusion layer increases with the increase of the chromium content, chromium distributes uniformly in the diffusion layer and no chromium is enriched. In the condition with the same aided infiltration time, the co-permeation rate will be promoted and phase constitution in the diffusion layer will transform from a single layer to a multi-layer with the increase of the chromium content. At the same chromium content, the phases in the diffusion layer change as the time goes on. Reaction between Fe and Zn is accelerated and the formation of Fe-Al phase decreases. When the diffusion process is performed at 600℃ for 3 h and the chromium content （w/%） in the Al-Zn-Cr infiltration powder is 5%, the obtained diffusion layer which is composed of α-Fe（Zn-rich）, Fe3Zn10, FeZn7 and FeAl phases is a compact multiple structure. The alloying layer has good oxidation resistance and cathodic protection.