The effect of saline environment on the fatigue behaviour of HVOF-sprayed WC–CrC–Ni coatings

Abstract

This paper presents the effect of saline environment on the fatigue behaviour of high-velocity oxygen fuel thermal-sprayed WC-CrC-Ni coatings. These coatings are used to improve the surface hardness, corrosion and wear resistance of components or products, in the place of hard chrome plating. Although so far many tests on the wear and corrosion of coating behaviour were carried, the conduct of the joint action fatiguea corrosive environment is not fully identified. In the frame of the experimental programme, similar axial fatigue tests at room temperature, on air or on specimens immersed in 3% NaCl solution and also chemical composition, structural analysis of the fracture surface were performed, using SEM and EDX. The saline environmentcauses material corrosion, generation of voids and microcracks on the specimen surface and their propagation through the specimen cross-section, accelerating the specimen failure.

Composite coating by TIG cladding with different rare earth oxides

“…So, a good coating with fewer cracks and pores is obtained. As the RE (CeO 2 , La 2 O 3 and Y 2 O 3 ) have great chemical reactivity and bonding force with the other elements, they easily form good inter-metallic bond and compound which in contrast becomes new nuclei which enhances the nucleation rate and refines the grain near the boundaries and hence, lesser defects, cracks and pores are visible [18,22,23]. But in the coating layer without RE material, there is high surface tension, low flow rate, and the high thermal stress of molten pools which are responsible for the generation of defects [16].…”

“…In this regard, WC in association with Ni gained a great demand in recent years. The combination has great affinity towards the formation of hard MMC coating on the parent material's surface because of the properties such as high density, high hardness and good metallurgical bonding in a molten state [17][18][19]. Additionally, the combined effect of coating different RE oxides (such as CeO 2 -La 2 O 3 , CeO 2 -Y 2 O 3 and La 2 O 3 -Y 2 O 3 ) with WC and Ni is limited on TC4 alloy (Ti-6Al-4V alloy).…”

Impact-sliding wear properties of PVD CrN and WC/C coatings

“…The oxidation pitting on the worn surface of the WC/C coating is caused by micro-holes in the coating [48,49]. Under repeated shear stress, the WC/C coating also exhibits slight micro-peeling in the impact zone but it is much milder than the damage to the CrN coating [50]. Therefore, the WC/C self-lubricating coating significantly improves the impact-sliding wear performance of the cemented carbide.…”

Tribo-behaviour of APS and HVOF sprayed WC–Cr3C2–Ni coatings for gears

“…The thermal sprayed WC coatings with improved tribological performance could be a capable alternative solution to the chromium plating in automobile and marine industries. The government rules about environmental issues related to hard chromium plating enforced the automotive industry to work on alternatives [1][2][3]. The atmospheric plasma spray (APS) and high-velocity oxyfuel (HVOF) techniques have been commonly used thermal spray variants for numerous applications.…”

“…The coatings deposited with various thermal spray variants, i.e. WC–Cr 3 C 2 –Ni [1], WC [3], WC–Co [4], WC–NiCr [5] and WC–CoCr [6,7] could be employed for brake pistons [8], gears [9], shock absorber rods [8] and engine components [3,10]. The primary tribological design objective of gear life is higher resistance to abrasive wear, erosion wear and corrosion.…”