稀土钕对H13钢TD处理组织及性能影响

Effcet of rare earh Nd on structure and property of coating by TD process on H13 steel

用加入0,0.3%,0.8%(质量分数)稀土钕(Nd)的盐浴分别对H13试样进行TD处理,使试样表面形成碳化钒(VC)渗层。通过比较加与不加稀土Nd所获得渗层,研究Nd对TD处理的影响。采用扫描电镜(SEM)、X射线衍射仪(XRD)和维氏显微硬度计对渗层的组织、物相和硬度进行测试分析。结果表明:加入Nd可以避免对H13钢处理时产生合金元素富集,合金元素聚集导致材料表面附近一区域组织粗大,影响材料性能。Nd可以提高渗层以及渗层和基体间过渡区的硬度,过渡区硬度的提高可以对高硬度层起到更好的支撑作用,利于增加渗层与基体的结合强度;Nd的浓度并非越高越好,本文中用含0.8%Nd的盐浴处理后的试样效果最好,渗层硬度可达2400~2500 HV。

Procedures of thermal diffusion( TD) process were carried out on specimens of H13 steel using salt baths containing 0,0. 3%,0. 8% of rare earth neodymium( Nd),and vanadium carbide( VC) coatings were formed on the surfaces of the specimens. Effect of Nd on the coatings was analyzed by comparing the coatings obtained by TD treatment with and without Nd added. The coatings were observed and examined by SEM,XRD and Vickers micro-hardness tester. Results show that Nd prevents alloys concentration from happening when H13 steel is being treated,which leads to coarse structure in certain area near the surface and reduces performances of material. Nd has the effect of enhancing hardness of both VC coating and hardness transition area between coating and substrate. Increased hardness of this area is able to provide better support for the coating,and adhesion of the coating can be eventually improved. Effect of vanadizing is not always improved as Nd addition to salt bath increases. In this work,specimen treated with salt bath containing 0. 8% Nd has the best performances,micro-hardness of which reaches as much as 2400-2500 HV.