Failure Analysis of a Chromium Plating Layer on a Piston Rod Surface and the Study of Ni-Based Composite Coating with Nb Addition by Laser Cladding

Abstract

The failure of a chromium plating layer on the surface of a piston rod was analyzed, and an Ni-based alloy mixed with a niobium (Nb) composite coating was investigated by means of stereomicroscopy, metallographic microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Vickers hardness testing, and wear testing. The results show that penetrating cracks were present in the chromium layer. Subsequently, the corrosion intensified, resulting in the bubbling, cracking, and peeling of the chromium layer. The cladding layer presented a structure morphology of planar crystalline at the bottom, dendritic at the middle, and equiaxial crystalline at the top. The solidification parameters, which were derived from simulation results, confirmed that the ratios between temperature gradient (G) and solidification speed (S) decreased, and the values of the cooling speeds increased from the bottom to the top of the cladding layer. With an increase in Nb content, the structure became gradually refined and uniformly dense. The cladding layer of the Ni-based alloy mixed with Nb was mainly composed of γ-Ni, Cr23C6, Cr7C3, NbC, and Ni3Nb. NbC could be formed in situ and presented itself in four forms: particles, dendrites, polyhedrals, and networks. The microhardness of the coating with 15% added Nb was enhanced to 400 HV0.2, and the wear resistance thereof was 11.14 times higher than the substrate. After the 15% Nb coating had aged for 16 h, the diffraction peak intensities of Cr23C6 and Cr7C3 significantly increased, and the volume fraction of granular NbC increased from 1.67% to 2.54%. The microhardness was enhanced to 580 HV0.2, and the wear resistance thereof was better than that of the chromium plating layer.

Synergistic effects of graphene additives and piston ring surface treatment on friction properties of engine oil

“…Li and Yuan [30], studied the CoNiW alloy coating on the 1045 steel as piston ring materials by electrodeposition method to greatly improve the wear resistance performance. Although previous research extensively examined the performance of coatings embedded with various nanoparticles [31][32][33][34][35], the focus has been primarily on the coatings themselves rather than their interaction with nano-additives in oil. However, the microscopic mechanisms involved are still unclear, and few studies on the synergistic effects of other chemical coatings with lubricant additives have been reported [36][37][38].…”

High-speed laser cladding of chromium carbide reinforced Ni-based coatings

“…Interconnected cracks lead to rapid deterioration under corrosive environments as was shown in Refs. [39,40]. Beneficial effects of cracks include relaxation of residual stresses and working as oil pockets in lubricating applications.…”

Effects of Niobium Carbide Additions on Ni-Based Superalloys: A Study on Microstructures and Cutting-Wear Characteristics through Plasma-Transferred-Arc-Assisted Deposition

“…Adding NbC to the superalloy specimen modified the size and shape of the MC carbides after solidification (Figure 4b,c). Large, blocky carbides were observed, and they corresponded to the NbC powder, which also contained considerable B content and trace Ti amounts; this can be attributed to the NbC-TiB2 composites formed during high-temperature PTA welding [30]. The presence of high-hardness NbC powder in the cladding layer matrix improved its wear resistance [31], and the NbC-TiB2 composites such as TiB2-an extremely hard ceramic compound with excellent wear resistance and oxidation stability-enhanced the wear characteristics of the Ni-based superalloy.…”