Room temperature nanoindentation creep of nitrocarburised AISI 4140 steel

ABSTRACT

Room temperature indentation creep behaviour of different regions of nitrocarburised AISI 4140 steel is investigated by employing the nanoindentation creep testing method in the present study. A structure consisting of a compound layer, a diffusion layer and a substrate is observed in the nitrocarburised AISI 4140 steel. The stress exponents are calculated from the loading curve produced by nanoindentation during the holding time. The results indicate that with the increase in distance from the material surface, the obtained stress exponent decrease. From the compound layer to the diffusion layer to the substrate, the stress exponent decreases rapidly first, and then decreases gradually revealing a deeper test point that yields a lower creep resistance. The correlations between the room temperature creep behaviour and the corresponding microstructure of nitrocarburising surface are discussed.

KEYWORDS:

• Nanoindentation creep
• nitrocurburised steel
• room temperature creep
• stress exponent

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors would like to acknowledge the support from National Natural Science Foundation of China (Grant no. 51875373). Yanyan Huang and Qinghua Zhou would also like to acknowledge the supports from the Fundamental Research Funds for the Central Universities (No. 2017SCU12021), the Aeronautical Science Foundation of China (No. 20160219001) and the China Postdoctoral Science Foundation (No. 2017M623026).