Study of the Thermochemical Surface Treatment Effect on the Phase Precipitation and Degradation Behaviour of DSS and SDSS

In this study, the effect of a plasma ion carburizing process to duplex and superduplex stainless steels (DSS and SDSS), at 925 °C for a long time, as thermochemical process influencing the microstructural evolution is presented. The objective is to analyse the diffusion elements’ influence on the precipitation of secondary phases after additional short thermal treatment. A comparison among the different treatments was performed after the resulting microstructures were analysed by Field Emission—Scanning Electron Microscope. Precipitation of secondary phases—sigma (σ), chi (χ), nitrides and carbides—seemed to occur during the treatments in a similar way for both steels (DSS and SDSS), although they showed a different morphology and precipitation mode. General corrosion behaviour of untreated and treated samples was investigated by potentiodynamic tests in order to prove their corrosion resistance. It was found that an improvement of the surface protection after the plasma carburizing process occurred.

Study on Upgradation in Carburizing Technologies for steel strength

Carburizing technologies are used to provide strength on low quality metals. This technology is being developing with novel improvements significantly. The carburizing process consists of, first releasing Carbon mono-oxide from charcoal material and then transfers carbon to raw metal. There are favorable upgradation in these technologies from researchers which have a paramount industrial importance. In Vacuum gas carburizing, the steel metal is carburized with (Acetylene and Propane) gases. These gases are at low pressure and high temperature. The results show that the metal is 1.5 times harder than its raw form. There are also used mathematical models to validate the results. It used gas and solid phases for validation. In pulse carburizing, carbon diffusion on steel is investigated with heat treatment. This process includes several carburizing stages. This process is based on Darken bi velocity and drift velocity. It accounts to demonstrate the kinetics of carbon transfer on steel surface. This design is very useful by regarding carburizing time for this process design. In Plasma carburizing, the mixtures of gases are used to harden the steel. The carburizing temperature was varied in cementite and martensitic. The favorable results show that these specimens have (Lower surface roughness, higher surface hardness and Low wear rate). It is a most novel diffusion controlled novel process till the present time. The carburized metal is used in industry by including (Turbine gears and Air craft engine). Henceforth, It is of great importance to study the carburizing technologies for providing better strength on metal.

Characteristics of AISI 420 Stainless Steel Modified by Low-Temperature Plasma Carburizing with Gaseous Acetone

In this research work, low-temperature carburizing of AISI 420 martensitic stainless steel was conducted at 460 °C for different amounts of time using an acetone source. The microstructure and phase structure of the carburized layers were characterized by optical microscope and X-ray diffraction. The properties of the carburized layers were tested with a microhardness tester and an electrochemical workstation. The results indicate uniform layers are formed on martensitic stainless steel surfaces, and the carburized layers are mainly composed of carbon “expanded” α (αC) and Fe3C phases. The property tests indicated that after plasma–carburizing, the hardness of the stainless steel surface can reach up to 850 HV0.1. However, the corrosion resistance of stainless steel decreased slightly, and the corrosion characteristic of stainless steel was altered from pitting to general corrosion. The semiconductor characteristic of the passivation film on stainless steel was transformed from the p-type for untreated specimens to the n-type for carburized specimens.