Nanomechanical, Tribological, and Scratch Properties of Electroless Ni-B-W Alloy and Ni-B-W-SiC Composite Coatings

Abstract

The electroless deposition process can develop composite coatings superior in mechanical and tribological characteristics. The deposited alloy matrix with the reinforcement of a hard ceramic phase can produce a stronger composite coating, favorable for industrial applications. The fabrication process of Ni-B-W-SiC electroless composite coating on steel substrate by reinforcing silicon carbide (SiC) in ternary Ni-B-W matrix is presented in this report. Characteristics of the developed composite coating are studied in reference to electroless ternary Ni-B-W alloy coating. These ternary alloy and composite coatings are also subjected to heat treatment (450 °C, 1 h) to observe structural changes. All coated samples are characterized with field emission scanning electron microscope, X-ray diffraction, inductively coupled plasma-atomic emission spectrometer (ICP-AES), and high resolution transmission electron microscope analyses to draw conclusions in comparative studies concerning morphological features, compositions, and phase structures. Cross-sectional and Raman spectroscopic examinations are performed to authenticate the presence of SiC phases in the alloy matrix. To get a further insight into characteristics features, various nanomechanical and tribological properties of these coatings are evaluated and subsequently co-related. Coatings developed with silicon carbide particles present in matrices show remarkable improvements in nano-hardness (H), reduced modulus (Er), yield strength, and fraction of plastic work done. Heat treatment imparts propitious effects on these mechanical properties due to the formation of harder nickel boride (Ni3B, and Ni2B) phases. Heat-treated Ni-B-W-SiC composite subjected to tribological and micro-scratch testing reveals a significant improvement in sliding wear and scratch resistance as compared to those in other coatings.