表面高铬高碳合金层耐蚀性能的研究

CORROSION RESISTANCE OF THE SURFACE WITH HIGH CHROMIUM AND HIGH CARBON ALLOY LAYER

在Q235钢表面进行双层辉光离子渗铬,表面铬含量约为40%.然后进行超饱和渗碳,表面含碳量达到2.7%左右,超过平衡碳计算值.随后进行淬火+低温回火热处理,使表面合金层获得马氏体基体上均匀分布的细小弥散碳化物组织,没有共晶莱氏体.经X射线衍射分析,合金化层碳化物类型为M23C6、M7C3,尺寸1～2μm,表面硬度达到1200HV左右.将双层辉光离子渗铬+渗碳淬火试样,在10%硫酸、3.5%NaCl水溶液和H2S富液(含H2S 5～8g/L,NH3*H2O 20g/L)中,进行电化学腐蚀试验.结果表明,渗铬试样在10%硫酸、3.5%氯化钠水溶液和硫化氢富液中的耐腐蚀程度比Q235基体试样分别提高了2.35、3.10、2.14倍.

A high chromium and high carbon alloy layer was produced on Q235 steel with the double glow plasma metallurgy. Alloying element Cr was penetrated into the Q235 steel in a vacuum chamber by glow discharge sputtering so that the content of Cr in the alloy layer was about 40% at the surface of Q235 steel. Then ultrasaturation carbonization made surface carbon content reach 2. 7%, which exceeded the calculation values of balancing carbon. Subsequently by quenching and low-tem2ering heat treatment the martensite matrix with uniform, compact and dispersed carbide structure distribution was formed without eutectic ledeburite at the surface alloying layer. X- ray diffraction analysis indicated that the types of the carbides were M23 C6 and M7 C3, with a dimension of 1 2μm. The surface hardness reached 1200HV around. In 10% H2SO4, 3. 5% NaCl and H2S pregnant solutions （H2S 5-8g/L, NH3 · H2O 20g/L）, the electrochemical corrosion experiments were carried out on the double glow plasma chromizing samples and Q235 steel samples. The results indicated that the corrosion resistance of the double glow plasma chromizing samples was 2. 35, 3. 10 and 2. 14 times higher than that of Q235 steel samples.