Case study: Wear mechanisms of NiCrVMo-steel and CrB-steel scrap shear blades

Abstract

Shear blades are extensively used in the recycling of metal scrap. A comparative study was conducted on used medium carbon NiCrVMo and CrB containing steel scrap shear blades to better understand their wear mechanisms under service conditions. The microstructure and hardness of worn cutting edges and bulk material were characterised by optical microscopy, scanning electron microscopy and microanalysis, X-ray diffraction analysis and macro/micro hardness testing. Moreover, tensile and Charpy impact properties were obtained from the bulk material. Several wear mechanisms were identified in both blades which are categorised in two main groups, i.e. spalling and progressive wear. The progressive wear due to abrasive, adhesive and oxidation wear was observed in both blades. In NiCrVMo-steel blades, spalling and crack propagation from surface/subsurface white etching layers mainly caused the severe wear. However, spalling due to delamination wear and crack propagation from severely deformed subsurface layers was the dominant severe wear mechanism in CrB-steel blades.

Electron Microscopy and Spectroscopy in the Analysis of Friction and Wear Mechanisms

“…Therefore, SEM images in BSE mode provide a convenient tool to characterize the distribution of secondary phases, the presence of oxides, or other compounds [25,29]. In addition, BSE imaging can also be employed to detect cracks and metallurgical defects, such as porosity and non-metallic inclusions [30].…”

“…If the analysis is paid more attention on one or more elements in an imaged area, the line-scan mode is operated by confining the scanning electron beam in a defined length, e.g., across a grain boundary or an object of interest, to get the relative (qualitative) profiles of the selected elements. Similarly, the scanning can be made in a pre-defined area, instead of a period of length, to obtain a two-dimensional relative distribution of the featured elements, which is known as element-mapping analysis [30].…”

“…For the latter, an improved understanding on the mechanisms has been attributed to the advances in laboratory techniques of materials analyses and characterization, especially the metallographic and spectroscopic techniques that are based on electron microscopy. This paper is a survey of the analytical electron microscopy techniques employed in the author's studies of wear mechanisms [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30].…”

“…Another obvious advantage of SEM is its large depth of focus, which allows imaging of three-dimensional features on most worn surfaces and wear particles. Moreover, most SEM instruments have also been equipped with powerful capability of chemical analysis, e.g., energy dispersive X-ray (EDX) spectroscopic analysis, which enables simultaneous microscopic observation and chemical analysis of wear features [25][26][27][28][29][30]. Transmission electron microscope (TEM) is the most widely used instrument in comprehensive characterization of materials, with its advantages of the best spatial resolution in observing extremely small species and the capability in performing combined metallographic, crystallographic, and spectroscopic analyses [17][18][19][20][21][22].…”

“…Details of the research can be found in previous publications [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. In particular, it has been found that, the sliding wear of vanadium-containing transition metal nitride TiAlN/VN coatings led to the formation of a multi-component Ti-Al-V-N-O tribofilm on the worn surface.…”