A study on coatability of marble dust on metal substrates

Marble dust is a hazardous construction/industrial waste generated during the extraction, cutting and polishing of marble-producing rocks. The present work explores the potential of marble dust to be used as a coating material on metal substrates. For this, the high-velocity oxy-fuel (HVOF) spraying route is adopted to deposit marble dust coatings on four different metallic substrates: mild steel, inconel, aluminum, and copper. Liquefied petroleum gas is used as the fuel and nitrogen as the carrier gas while the coating deposition is performed by varying the spray distance over a range from 50 mm to 250 mm. The coating microstructure is studied using a scanning electron microscope (SEM) and the developed phases are identified using an x-ray diffractometer. The developed coatings are characterized in terms of deposition efficiency, coating thickness and adhesion strength. It is found that the coatings exhibit fairly good interfacial adhesion and thickness values that varied quite significantly with the spray distance. Maximum deposition efficiency of about 68 % is obtained for the copper substrate when the deposition is performed at a spray distance of 100 mm. This experimental investigation thus shows that despite being a waste, marble dust is eminently coatable on several metallic substrates.     

Optimization of dry sliding wear behaviour of industrial wastes reinforced aluminium based metal matrix composites

Marble dust and basalt powder are industrial waste generated during the machining of marble stone and basalt rock. This paper presents an approach for the optimization of dry sliding wear parameters of aluminium 7075 reinforced with marble dust and basalt powder hybrid metal matrix composite using Taguchi based grey relational analysis. In this work, the composite is fabricated by stir casting technique and the wear parameters namely load, sliding velocity and sliding distance are optimized with consideration of multi responses such as wear rate and coefficient of friction. Experiments are conducted as per Taguchi's L9 orthogonal array. A grey relational analysis is carried out and grey relational grade is obtained. Based on the grey relational grade, optimum level of wear parameters has been identified by analysis of variance. The test results are validated by conducting the confirmation test. Experimental results have shown that the sliding velocity is the most effective factor among the control parameters on dry sliding wear, followed by the sliding distance and load. Finally, the micro structural investigations on the worn surfaces are performed by scanning electron microscope.