Evolution of pre-oxide layer during subsequent plasma nitriding. (June 2018)

• Record Type: Journal Article
• Authors: Tang, Lei; Sun, Fei; Miao, Xiaoji; Li, Jingcai; Hu, Jing
• Is Part Of: Vacuum. Volume 152(2018)
• Page Start: 337
• Page End: 339
• Publication Date: 2018-06
• Subjects: Pre-oxide layer -- Plasma nitriding -- Plasma oxynitriding -- Evolution; Vacuum -- Periodicals; 621.55
• DOI: 10.1016/j.vacuum.2018.03.057
• Languages: English
• ISSNs: 0042-207X

Abstract

Abstract: Plasma pre-oxidizing was conducted and evolution of the pre-oxide layer during plasma nitriding was primarily investigated. For comparison, plasma oxynitriding was also processed after pre-oxidizing. Scanning electron microscopy, X-ray diffraction and optical microscope were used to analyze the evolution of pre-oxide layer. The results showed that a pre-oxide layer in the form of nanoparticles formed during plasma pre-oxidizing was gradually decomposed in subsequent plasma nitriding process, and it almost disappeared after 1 h. Meanwhile, the decomposition could promote nitrogen atoms diffusing inward, thereby enhance nitriding efficiency. However, the pre-oxide layer could not be decomposed in the subsequent plasma oxynitriding; on the contrary, the oxide layer thickness gradually increased, along with the transformation of Fe3 O4 to Fe2 O3, which resulted in excessive oxidation and decrease of oxynitriding efficiency. Therefore, the research brought new knowledge to plasma treatment process and of significant guiding effect in real applications. Highlights: Evolution of pre-oxide layer during plasma nitriding was primarily investigated. The oxide layer was gradually decomposed in PN process and disappeared after 1 h. The pre-oxide layer could not be decomposed in the subsequent PON.