Abrasive Wear of High-Carbon Low-Alloyed Austenite Steel: Microhardness, Microstructure and X-ray Characteristics of Worn Surface

A high-carbon, high-silicon steel (1.21 wt% C, 2.56 wt% Mn, 1.59 wt% Si) was subjected to quenching from 900 and 1000 °C, resulting in microstructures containing 60 and 94% of retained austenite, respectively. Subsequent abrasive wear tests of quenched samples were performed using two-body abrasion and three-body abrasion testing machines. Investigations on worn surface and subsurface were carried out using SEM, XRD, and microhardness measurement. It was found that the highest microhardness of worn surface (about 1400 HV0.05) was achieved on samples quenched from 900 °C after three-body abrasion. Microhardness of samples after two-body abrasion was noticeably smaller. with a maximum of about 1200 HV0.05. This difference correlates with microstructure investigations along with XRD results. Three-body abrasion has produced a significantly deeper deformed layer; corresponding diffractograms show bigger values of the full width at half maximum parameter (FWHM) for both α and γ alone standing peaks. The obtained results are discussed in the light of possible differences in abrasive wear conditions and differing stability of retained austenite after quenching from different temperatures. It is shown that a structure of metastable austenite may be used as a detector for wear conditions, as the sensitivity of such austenite to phase transformation strongly depends on wear conditions, and even small changes in the latter lead to significant differences in the properties of the worn surface.

First-Principles Study on the Structural, Electronic and Elastic Properties of Alloyed Austenite with Co and Ni

The crystal structure of alloyed austenite distorted after Ni and Co replaced Fe. The crystal type of austenite changed from cubic structure to tetragon or orthorhombic structure due to the influence of Co and Ni. The ratio (B/G) for γ-Fe (C) is equal to 2.841, which is higher than that for other alloyed austenite with Co and Ni. The workability of alloyed austenite with Co and Ni are poorer than γ-Fe (C). The formation of alloyed austenite needs more energy than γ-Fe (C) at ambient conditions.

Ferrite Formation from Austenite; Effects of Length and Time Scales, Interface Type and Chemistry

The growth of ferrite from alloyed austenite can take many forms: Widmanstätten ferrite and “plessites” in meteoric Fe-Ni-Co; ferrite layer growth under decarburization conditions; grain boundary precipitation and Widmanstätten ferrite and bainite in alloy steels. This contribution considers ways in which these different aspects of austenite decomposition can inform one another.

Silicon Influence on Corrosion Properties of Austenitic Stainless Steels

In the present paper there are presented results concerning comparative corrosion resistance of some austenitic stainless steels, with or without silicon content. The silicon content is varying in the range of 1-5 %, in a matrix of alloyed austenite, containing 20% Cr and 15-18%Ni and with very low carbon contents (lower than 0,03% C). There are investigated different types of corrosion resistance: intergranular corrosion in nitrogen media, stress corrosion resistance in chloride media, and transpassive behaviour in sulphuric media. The testing media contained nitrogen, as it follows: Huey test (65% HNO3, at boiling temperature, 244 hours maintain), and 5N HNO3 +1g/l Cr6+ (144 h, at boiling temperature). The media containing chloride is 45% MgCl2 at boiling temperature, with a period of 1000 hours. The transpassive behaviour is tested in 10% HSO4. The investigations were made by optic and electronic microscope, and the corroded surfaces were examined by scanning electron microscopy.