Effect of laser post-treatment on Al 2O 3-TiB 2-TiN composite coating with free hBN

Abstract

The development of nanostructured, hard, and wear-resistant composite coating of Al 2O 3, TiB 2, and TiN on low carbon steel (AISI 1025) substrate by combined self-propagating high-temperature synthesis (SHS) and laser surface alloying (LSA) has already been communicated in the author's previous publications. The coefficient of friction of the coating (with WC-Co as counterbody) is also found to have reduced substantially with the presence of free hexagonal boron nitride (hBN) in it. The occurrence of free hBN has been made possible by putting excess hBN in the precursor mixture which is supposed to undergo combined SHS and LSA. This has also been reported in one of the previous publications. This reduction in coefficient of friction is achieved at a cost of a marginal reduction in the microhardness as well as the specific wear rate as the free hBN in the coating matrix causes some softening. Laser posttreatment causes distinct enhancement in the microhardness and wear resistance of the coating while augmenting the favorable effect of free hBN on the coefficient of friction. © Springer-Verlag London Limited 2011.