Drying of Sponge Media Using Swirling Fluidized Bed Dryer

Surface preparation is a process of treating a surface to increase its attraction to coatings and imperative to ensure satisfactory coating can be attained. Conventional techniques of surface preparation usually involve blasting of abrasive material on the surface which usually associated with airborne debris and hazardous contaminant from the process. A relatively new technology in surface preparation is the usage of sponge media as an alternative to the conventional abrasive material. Being soft and elastic, sponge media can reduce airborne emission from surface preparation significantly while being able to be recycled. Unfortunately, the recovery of used sponge media becomes difficult during rainy conditions in which the sponge absorbs water and quickly becomes saturated. Therefore, this paper presents the drying characteristics of sponge media using a swirling fluidized bed dryer (SFBD) for rapid drying to overcome the long, inefficient sun drying as per current practice. Several laboratory scale experiments were carried out to dry water laden of the sponge media in the SFBD. Three bed loadings of 1.7, 2.0 and 2.3 kg were used at drying temperatures of 80°C, 90°C and 100°C. The experimental works revealed the excellent potential of the SFBD in drying the sponge media rapidly. The behaviour of moisture ratio and drying rate against time were discussed. Keywords: Sponge media drying, Swirling Fluidized Bed Dryer (SFBD), Moisture ratio, Drying rate

Properties of TiC-Ni Based Coatings Deposited by Different HVOF Spraying

Hardmetal-like coatings of the TiC-Ni system are potential for use as wear, corrosion and heat resistant coatings in various operation conditions. Our previous works [1-12] have shown that these materials are well sprayable using different thermal spray processes such as plasma, D-Gun and HVOF spraying. Since HVOF spraying is today the most important process used to apply carbide based coatings, this study was carried out in order to evaluate more systematically the sprayability of these novel spray powders and the influence of HVOF spray parameters on some coating properties. Coating samples were prepared by using DJ Hybrid gun with propane as a fuel gas, and a CDS gun with hydrogen fuel gas. Oxygen flow rate was varied in both cases for changing the flame temperature. Microstructure, phase composition, hardness, and abrasion wear resistance of the coated samples were investigated. The results showed that both HVOF processes used give satisfactory coating properties and that the use of high oxygen flow rates is beneficial for improving the wear resistance of the coatings. Powders with fine particle size are beneficial in the DJ Hybrid process; the use of coarse powders results in coatings with somewhat higher wear rates. The optimum spray condition for the TiC-Ni system powders differs from that typically used for conventional WC-Co and Cr3C2-NiCr powders by a higher flame temperature.