Sliding wear behaviour of a Cr-base alloy after microstructure alterations induced by friction surfacing

Abstract

Friction surfacing is a method suitable to generate a wide variety of metallic coatings by means of frictional heating and severe shear deformation. It is a solid-state joining method, and therefore may be applied to non-fusion weldable as well as non-deformable brittle materials, as Cr-based alloys are. In the present study coatings of Cr60Ni40 alloy are generated onto Nimonic 80A substrates. Microstructural investigations of the coating material are carried out and compared to the usual cast state. The wear behaviour of the coatings as well as the cast material is examined under reciprocating sliding against 52100 ball bearing steel by means of a ball-on-flat test rig, lubricated with silicone oil to prevent oxidation. In this tribological system, wear takes place by abrasion with microploughing being the predominant submechanism, surface fatigue as well as adhesion by materials transfer of Cr60Ni40 from the flats to the steel balls. White etching layers form on Cr60Ni40 underneath the worn surfaces, which show cracks and delaminations. The amount of wear of all coatings is within the same magnitude compared to the cast state but slightly smaller. This can be explained by the distinctly finer microstructure (grain boundary strengthening) and a high degree of supersaturation of the solid solutions (solid solution strengthening) within the coatings. The results of this study show that it is possible to generate coatings of brittle alloys like Cr60Ni40 by friction surfacing, which show a slightly better wear behaviour under reciprocating sliding. Thus, in combination with a ductile substrate, these coatings are likely to extend the range of applicability of such high-temperature wear and corrosion resistant alloys.

Surfacing – Technologies and Layer Properties (A Review)

“…The specific in this case is that no heating is required for the deposition of the bed, and the thermal treatment is at relatively low temperatures (2900C). Both in this case and in the friction stir surfacing (FSC) [43], [44], [45], [46], [47], the melting temperatures of the substrate are not reached. Therefore, diffusion processes have a significant effect on the final result.…”

“…divided into the following main groups. The microstructure is examined by optical (OM) [1], [9], [17], [21], [23], [27], [30], [31], [36] ], [42], [43] and electron microscopy (SEM) [1], [10], [11], [14], [21], [22], [23] , [33], [39], [46], [47]. The phase composition is determined by the X-ray diffractometer [18], [23], [27], [31], [33], [36], [39], [45], the transmission diffraction electron microscopy [18] and energy-dispersive X-ray spectroscopy [14], [22], [30], [33], [39].…”

Effect of Microstructure on Wear Resistance of Low-Alloy High-Strength Wear-Resistant Steel

“…Compared to steels R and B, steels J and S had more contents of Cr and Mo elements, with the largest Cr content up to 33 times and the largest Mo content 9 times those of the other two. Cr element contributes to carbide formation and improvement of the hardenability [12]. Mo element is more efficient in increasing the hardenability.…”

The Effect of Type of Welding Sequence During Hardfacing Chromium Cast Iron for Erosion Resistance

“…There are also many other opportunities to improve the properties of the surface layer, eg. by the use of welding techniques as melting surface or surfacing with various of materials and different heat input [4][5][6][7][8][9][10][11][12][13]. By using self shielded cored wires it became possible to also receive materials about the structure of chromium cast iron welding methods by welding [14][15][16][17][18].…”