A novel plasma surface engineering process has been developed for engineering the surfaces of austenitic stainless steels to achieve combined improvements in wear and corrosion resistance. The process employs carbon as the major alloying species in the glow discharge of a plasma, facilitating the diffusion of carbon into the surfaces of various austenitic stainless steels and forming a precipitate free layer supersaturated with carbon at relatively low temperatures. This low temperature plasma surface alloying process produces a surface engineered layer several tens of micrometres thick, which has a high hardness together with excellent wear and corrosion resistance. The present paper describes various aspects of the novel process, concerning processing, structures, properties, and applications to engineering components.

A low temperature plasma carburising process has recently been developed to engineer the surfaces of austenitic stainless steels to achieve combined improvements in wear and corrosion resistance. T he present paper discusses the structural characteristics of the carburised layers produced on AISI type 316 steel at temperatures between 400 and 600°C. It was found that at low temperatures (<520°C), the carburised layers produced were precipitation free and comprised a single phase, which had a face centred cubic structure and was identified as expanded austenite owing to the supersaturation of carbon in austenite. T he carburised layer was in a deformed and distorted state. High densities of twins, stacking faults, and dislocations were found in the expanded austenite. T he degree of lattice expansion was estimated and was found to vary with processing temperature and depth in the layer. Precipitation of carbides (mainly Cr 7 C 3 ) occurred when the carburising temperature was relatively high (for example 550 and 600°C). In addition, stress induced martensite was found, particularly in the carburised layers produced at relatively high temperatures.MST /4313

Theoretical studies suggest that the final earthquake (EQ) and neural-seizure dynamics should have many similar features and could be analyzed within similar mathematical frameworks. Herein, by monitoring the temporal evolution of the fractal spectral characteristics in EEG time series and pre-seismic electromagnetic (EM) time series we show that many similar distinctive symptoms (including common alterations in associated scaling parameters) emerge as epileptic seizures (ES) and EQs are approaching. These alterations reveal a gradual reduction of complexity as the catastrophic events approach. The transition from anti-persistent to persistent behaviour may indicate that the onset of a severe crisis is imminent. The observations find a unifying explanation within the school of the "Intermittent Criticality".

Titania films, 5-9 mm in thickness, were produced on commercial purity titanium by a direct current (DC) plasma electrolytic oxidation (PEO) process using 5 to 20 A dm 22 current densities in 5 to 15 g L 21 trisodium orthophosphate electrolytes. Phase analyses (composition and crystallite size) were carried out using X-ray diffraction and TEM techniques. Residual stresses associated with one of the crystalline coating phases (anatase) were evaluated using the X-ray diffraction Sin 2 y method. SEM and TEM techniques were utilised to study the cross-section and surface morphologies and nanofeatures of the PEO titania coatings. Variations in the proportions of anatase and rutile phases, surface morphologies, coating thicknesses and associated internal stresses are correlated with the current density and electrolyte concentration used during the DC PEO process on titanium. Direct and shear stresses in the anatase are found in the range 270 to 2331 and 217 to 2167 MPa respectively.

Abstract. In this study, advanced surfaces and coatings have been developed using plasma thermochemical treatment, PVD coating, electroless Ni-BN plating and duplex surface engineering to produce low-friction and wear-resistant surfaces for cast iron stamping tools. Their microstructural and nano-mechanical properties were systematically analysed and the tribological behaviour of these new surfaces and coatings were evaluated. The experimental results have shown that under dry sliding condition, the tribological behaviour of aluminium differed great from that of steel regardless of the counterpart material. Highly reactive aluminium had a strong tendency to solder with tool surfaces during dry sliding. However, the lubricity of gray cast irons can be significantly improved by Ni-BN and DLC coatings. The coefficient of friction reduced from about 0.5 for untreated cast irons to about 0.2 sliding against aluminium. Duplex treatment combining plasma nitrocarburising with lowfriction coatings showed superior durability than both DLC and Ni-BN coatings.