不锈钢表面等离子渗铪及渗碳后的抗高温氧化行为

High-temperature Oxidation Behavior of Austenite Stainless Steel with Plasma Surface Hafnizing and Carburization

研究了0Cr_（18）Ni_9Ti奥氏体不锈钢等离子渗铪以及渗铪后进行渗碳并在静态空气中的抗高温氧化行为。研究表明：渗铪合金层厚度为35μm,渗层连续致密无孔洞,与基体呈冶金结合,表面物相主要有Hf、HfC、Hf_2Fe;渗铪＋渗碳层厚度为100μm,渗层弥散分布许多粒状和短棒状碳化物颗粒,尺寸在1~2μm,主要类型为MC、M_7C_3、M_（23）C_6型。1050,1100℃下氧化时渗Hf试样氧化速率约为基材的1/3、1/8,而渗Hf＋渗C试样约为1/8、1/25,随着氧化温度升高时,氧化速率增大,增幅及氧化增重均为渗Hf＋渗C试样〈渗Hf试样〈基材,且氧化增重近似符合抛物线规律;依次渗Hf和渗C后,经过高温氧化,试样表面合金元素降低、Hf含量升高,表面剥落得到改善,氧化缺陷减少、孔洞变小,Hf起到固化表面氧化物层、提高固溶强化的作用,HfC等碳化物以及HfO_2可以有效降低氧离子的扩散速率,显著提高抗高温氧化性能。

High-temperature oxidation resistance in static air of 0Cr18Ni9Ti stainless steel（substrate for short）,and that of the substrates after hafnizing process and hafnizing＋carburizing process were investigated.The results show that the Hf-alloyed layer of 35 μm in thickness is continuous and dense with no holes.It combines with the matrix as a metallurgical bond,whose surface phase is Hf_2Fe,HfC and Hf;however,the Hf＋C layer is 100 μm in thickness,many granular and short rod carbide particles with sizes 1~2 μm distribute dispersively,and the main types are MC,M_7C_3 and M_（23）C_6.The oxidation rate of the Hf-alloyed sample at 1050 ℃ and 1100 ℃ is just 1/3 and 1/8 of that of the substrate,respectively,while that of the Hf＋C layer sample is its 1/8 and 1/25,respectively.The oxidation rate increases as the temperature rises,the rate and oxidation mass is in the order of Hf＋C layer sample Hf-alloyed sample substrate,and the oxidation mass obeys the parabolic law.After hafnizing and carburizing followed by high-temperature oxidation,the surface alloying element content declines,Hf content increases,surface flaking improves,oxidation defects decrease and holes turn smaller.Hf can solidify the surface oxide layer and improve solid solution strengthening.Carbide particles including HfC and oxides such as HfO_2 can reduce the diffusion rate of oxygen ions and improve the oxidation resistance markedly.