Low pressure plasma induced surface changes of some stainless steels

Abstract

The present paper reports on the interaction of low-pressure plasma (LPP) with the surfaces of different stainless steels (SS) (viz. austenitic, martensitic, and ferritic). Plasma treatment was standardized by optimizing the power and duration of plasma exposure. The criteria for such standardization were the extent of decrease in contact angle and hence increase in surface energy (SE), which would increase the lap shear strength (LSS) of these surfaces in the form of joints using phenolic resin. It was found that argon LPP was more effective than the argon‑oxygen LPP and, the best results were obtained with a plasma exposure of 500 W power for 20 min. The LSS of SS316 got improved by almost 100% for the plasma-treated surface compared to the untreated one. Contact angles got reduced to different extents for all the three types of SS, and a significant improvement (~175%) in SE was observed. The increase in SE was supported by atomic force micrographs that showed a decrease in the surface roughness . X-ray photoelectron spectroscopy (XPS) indicated a significant change in the surface chemistry due to the Ar-LPP treatment. • Maiden effort to modify the various kinds of SS surfaces using low pressure plasma • Optimized plasma parameters (Gas - Argon, Power-500 W, Time - 20 min.) • Significant improvement in surface energy (~175%), lap shear strength (~100%) • Surface roughness decreased and changed in the chemistry of SS surfaces.