Indentation and scratch testing – experiment and simulation

Most modern wear resistant materials feature a multiphase microstructure and the macroscopicwear behavior is controlled by the local mechanical properties of the single phases. Indentationtesting and in particular nanoindentation allows for the local mechanical characterization ofmaterials and their phases. This paper addresses the determination of important mechanicalparameters such as hardness, Young’s modulus and indentation energy parameters of singlephases in multiphase wear resistant materials. Important influencing factors such as matrixinfluence on the indentation results of an embedded hard phase, the indentation-size-effect (ISE),the effect of crystallographic orientation, and the fracturing behavior of hard phases are addressed.In addition, the results of scratch tests on the cold work tool steel X210Cr12 and a WC-Co hardmetal are presented in order to investigate aspects of the mechanical behavior under abrasion.The deformation behavior under indentation and scratch loading was analyzed by scanningelectron microscopy (SEM) and atomic force microscopy (AFM). Besides the experimentssupplementary numerical simulations of indentation and scratching testing with the use of theFinite-Element-Method (FEM) are presented

Influence of the PM-Processing Route and Nitrogen Content on the Properties of Ni-Free Austenitic Stainless Steel

Ni-free austenitic steels alloyed with Cr and Mn are an alternative to conventional Ni-containing steels. Nitrogen alloying of these steel grades is beneficial for several reasons such as increased strength and corrosion resistance. Low solubility in liquid and δ-ferrite restricts the maximal N-content that can be achieved via conventional metallurgy. Higher contents can be alloyed by powder-metallurgical (PM) production via gas–solid interaction. The performance of sintered parts is determined by appropriate sintering parameters. Three major PM-processing routes, hot isostatic pressing, supersolidus liquid phase sintering (SLPS), and solid-state sintering, were performed to study the influence of PM-processing route and N-content on densification, fracture, and mechanical properties. Sintering routes are designed with the assistance of thermodynamic calculations, differential thermal analysis, and residual gas analysis. Fracture surfaces were studied by X-ray photoelectron spectroscopy, secondary electron microscopy, and energy dispersive X-ray spectroscopy. Tensile tests and X-ray diffraction were performed to study mechanical properties and austenite stability. This study demonstrates that SLPS process reaches high densification of the high-Mn-containing powder material while the desired N-contents were successfully alloyed via gas–solid interaction. Produced specimens show tensile strengths >1000\ua0MPa combined with strain to fracture of 60\ua0pct and thus overcome the other tested production routes as well as conventional stainless austenitic or martensitic grades