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Slurry erosion of turbine components is a serious problem in most of the hydraulic power plants all around the world. Although some counter measures such as catchment area treatment to reduce the amount of sand particles going through the turbine components and modifying the hydraulic shape of turbine to reduce slurry erosion have been taken, still slurry erosion is responsible for heavy economic losses. Research is also in progress for improving the surface properties of the turbine components by the application of thermal sprayed coatings. Among various thermal spray processes, high-velocity oxy fuel (HVOF) spray process is a relatively industrially established and economical process. In this paper, an attempt has been made to describe HVOF thermal spray technology. Further, this paper presents a tutorial introduction, comprehensive history, and review of research work done on the use of this technique to provide protection against slurry erosion of some metals and alloys with a special emphasis on the hydraulic turbine steels. [ABSTRACT FROM PUBLISHER]

Abstract: Tribological behaviors of plasma-sprayed conventional and nanostructured Cr2O3–3%TiO2 ceramic coatings (i.e., CC3T and NC3T, respectively) using pin on disc type dry sliding and pot type slurry erosion test were investigated in the present work. The experimental results indicated that there were two main wear mechanisms, plastic smearing and adhesive tearing, in the worn coatings under dry sliding. Plastic smearing corresponded to a lower average friction coefficient and wear rate, while adhesive tearing corresponded to higher values. The erosive environment selected for the slurry erosion experiments include 10, 20 and 30% of SiO2 slurry concentrations in water with particle size 75–106μm. The main damage mechanism observed in all the coatings submitted to slurry erosion were the formation and propagation of brittle cracks resulting in the detachment of coating surface material. Microstructural investigation was also carried to investigate the wear and erosion mechanism of the coatings using FE-SEM and EDS analysis. Properties like microhardness and porosity were also investigated for these coatings. Tribological performance of NC3T was better as compared to CC3T as observed in the present work. [Copyright &y& Elsevier]

Abstract: This paper presents a study on the role of nickel content on the slurry erosive wear, strength and impact toughness behaviour of permanent moulded toughened austempered ductile iron (PMTADI) samples subjected to a special austempering heat treatment. The nickel additions were made at five levels ranging from 0.5 to 2.5% in steps of 0.5%. Toughened ADI samples have shown an increase in slurry wear and impact toughness and a slight reduction in tensile strength than samples subjected to conventional austempering heat treatment. The results indicate that there is a significant improvement in slurry erosion resistance for 2.0% nickel PMTADI samples. Samples containing 2.0% nickel shows superior slurry erosion and impact toughness than samples containing either 1% or 2.5% nickel content. The retained austenite content, distribution of bainite and the matrix microstructure play a vital role on the slurry erosive wear and mechanical properties of PMTADI samples. [Copyright &y& Elsevier]

Material loss due to erosion is a serious problem associated with the flow of solid-liquid mixtures. In the present work, erosion wear tests have been carried out in a slurry pot tester for seven different ductile type materials namely aluminum alloy (AA6063), copper, brass, mild steel, AISI 304L stainless steel, AISI 316L stainless steel, and turbine blade grade steel using three different erodents namely, quartz, alumina, and silicon carbide. Experiments have been performed at different orientation angles of target material at the velocities of 3, 6, and 8.33 m/s for solid concentrations of 10%, 20%, and 30% (by weight) and particle sizes of 363, 550, and 655 μm. The contribution of cutting wear in the total wear of ductile material at various orientation angles has been determined. It is observed that the maximum cutting wear angle for the ductile material depends on its hardness and a correlation is developed for its prediction. Also a methodology is proposed for estimation of the total erosion wear rate as a contribution of cutting and deformation wear rates. It is seen that this procedure results in an error of ±18% in estimation of erosion wear rate for the present experimental data. [ABSTRACT FROM AUTHOR]

Abstract: Conditioning of polishing pads during chemical mechanical planarization (CMP) of wafers is a critical process for maintaining productivity and quality control in the semiconductor industry. This investigation aims at developing a CMP diamond conditioner of a new concept and hence improving the conditioning performance. The novel diamond conditioner was fabricated by coating diamond films on a Si3N4 substrate with regularly patterned protrusions. Thanks to the uniform distribution and constant height of protrusions, the novel conditioner exhibited superior performance and durability over the current conditioner, which contains bonded diamond grits of various sizes and shapes with unequal heights. Characterization of the developed novel diamond CVD conditioner has also been made. [Copyright &y& Elsevier]