Abstract:Weld deposits are one of the most used economical ways of the wear resistance increase. The study compares the characteristics of the overlay material welded-on and the abrasive wear resistance. The research has been carried out using hardfacing alloys reinforced with primary chromium carbides and complex carbides. The overlay material was deposited on the low-carbon steel S235JR using the gas metal arc welding (GMAW) method. Four different commercial overlay materials were studied in terms of the microstructure effect. The abrasion wear testing was carried out using the abrasive cloth of grit 120 according to CSN 01 5084. The microstructure characterisation and surface analysis were made using optical and scanning electron microscopy. The results illustrate a significant effect of primary carbides on the abrasive wear resistance of weld deposits.
Abstract:Hardfacing is one of the most useful and economical ways to improve the performance of components submitted to severe wear conditions. This study has been made for the comparison of microstructure and abrasion resistance of hardfacing alloys reinforced with chromium carbides or complex carbides. The hardfacing alloys were deposited onto ČNS EN S235JR low carbon steel plates by the gas metal arc welding (GMAW) method. Different commercial hardfacing electrodes were applied to investigate the effect of abrasive particle size on abrasive wear resistance. The abrasion tests were made using the two-body abrasion test according to ČSN 01 5084 standard, abrasive cloths were of grits 80, 120, 240, and 400. Microstructure characterisation and surface analysis were made using optical and scanning electron microscopy. The results show the different influence of abrasive particles size on the wear rate for different structures of Fe-Cr-C system. The structures without primary carbides are of high abrasive wear rate, which increases nonlinearly with the increasing abrasive particle size. On the contrary, the structures containing primary carbides are of low abrasive rates and theses rates increase linearly with the increasing abrasive particle size.
It has long been known that horse sweat has a relatively high content of albumin (Leclerc, 1888; Smith, 1890) and a small quantity of globulin (Smith, 1890). Other compounds of protein character are not mentioned by these authors.The presence of mucoprotein in human thermal sweat has been reported elsewhere (Jirka & Kotas, 1957), and Evans, Nisbet & Ross (1957) have demonstrated histochemically the presence of mucoprotein in horse sweat glands. It was therefore decided to look for mucoprotein in the sweat of the horse resulting from the exertion of racing. The opportunity has also been taken, in one instance, to analyse sweat resulting from emotion and to compare it with that after physical exertion of the same animal. Attention has been paid particularly to the concentrations of protein and electrolyte in the sweats.In this paper mucoprotein is accepted as a protein substance of which about 10% consists of hexosamine. METHODSThe sweat of three race-horses (mares) was collected after physical exertion and that of another mare, which sweated copiously immediately before a race, was collected both after pre-race emotion and after exertion. The sweat, which formed a foam, was scraped from the neck of the animal immediately after a race. On the occasion when emotional sweat was collected the animal's neck was dried before it ran. On each occasion a dirty brown fluid was obtained, which was freed from impurities (hair, dust, grains of sand) by centrifugation; after being filtered the fluid remained strongly opalescent or turbid. On the addition of sulphosalicylic acid a copious precipitate occurred.Total nitrogen was estimated by the micro-Kjeldahl method. The nitrogen content of the filtrate, obtained after removal of proteins by adding to the sweat an equal volume of 20% sulphosalicylic acid, is referred to here as 'non-protein nitrogen'. This filtrate has been shown to contain mucoprotein. The precipitated protein calculated from the nitrogen difference is, on the basis of examination of the sweat by electrophoresis, accepted as albumin and globulin.The presence of mucoprotein was polarographically investigaked by Brdicka's filtrate reaction,
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