State of the Art of Laser Hardening and Cladding

In this paper an overview is given about laser surface modification processes, which are developed especially with the aim of hardness improvement for an enhanced fatigue and wear behaviour. The processes can be divided into such with and without filler material and in solid-state and melting processes. Actual work on shock hardening, transformation hardening, remelting, alloying and cladding is reviewed, where the main focus was on scientific work from the 21st century

Plasma Induced On Indenter Balls

There is an increasing demand to enable high throughput experimentation to characterize and develop new materials in a very short time. The investigated hardness measurement method differs from conventional hardness measurements in how the force is applied. The new method is based on laser-induced shockwaves. A shockwave is created with a nanosecond pulsed TEA CO2 laser on top of an indenter. The pressure of the shockwave is used to push an indenter inside a workpiece. A quadratic laser focus area of 4 mm², having a diagonal larger than the indenter diameter, leads to interactions of the laser beam with the surrounding material, which affects the plasma formation and results in heating of the material underneath. Material heating decreases the yield point and accordingly the hardness. Therefore, influence of pulse energy and plasma formation on heating of material are investigated to understand the interaction between the high intensity laser beam, the indenter and the material underneath. It is shown that a 3 mm indenter diameter reduces the maximum estimated temperature of the workpiece (X5CrNi18-10) underneath down to 64°C. With an additional positioning unit in combination with indenter diameter of 3 mm or larger no significant heat input was obtained anymore in the workpiece underneath

Biodegradability of organic matter associated with sewer sediments during first flush

The high pollution load in wastewater at the beginning of a rain event is commonly known to originate from the erosion of sewer sediments due to the increased flow rate under storm weather conditions. It is essential to characterize the biodegradability of organic matter during a storm event in order to quantify the effect it can have further downstream to the receiving water via discharges from Combined Sewer Overflow (CSO). The approach is to characterize the pollutograph during first flush. The pollutograph shows the variation in COD and TSS during a first flush event. These parameters measure the quantity of organic matter present. However these parameters do not indicate detailed information on the biodegradability of the organic matter. Such detailed knowledge can be obtained by dividing the total COD into fractions with different microbial properties. To do so oxygen uptake rate (OUR) measurements on batches of wastewater have shown itself to be a versatile technique. Together with a conceptual understanding of the microbial transformation taking place, OUR measurements lead to the desired fractionation of the COD. OUR results indicated that the highest biodegradability is associated with the initial part of a storm event. The information on physical and biological processes in the sewer can be used to better manage sediment in sewers which can otherwise result in depletion of dissolved oxygen in receiving waters via discharges from CSOS