INFLUENCE OF REMANIUM GM 700 CONSECUTIVE SMELTING ON STRUCTURAL AND MECHANICAL ALLOY PROPERTIES

Abstract

The authors of the given article have studied the changes in structural and mechanical properties of Remanium GM 700 alloy caused by its consecutive smelting. To carry out mechanical testing the initial alloy pattern has been consecutively smelted 6 times according to the mode indicated by the producer, namely at melting temperature 13700 С and holding time of 10 minutes. Three types of coupons were produced at each smelting: 1. Coupon for the examination of microhardness in the form of flat parallel plate measuring 10х10х2 mm3 . 2. Coupon for the measurement of compliance modulus in the form of cylinder 36 mm high and 3mm in diameter. 3. 10 coupons for stretching in the form of bilateral spades with the body measuring 0.4х5х25 mm3 . Stretching stress-strain curves were registered with the deformation machine MRK-1 at the speed of 0.2 millimeters per minute. Conventional plasticity limit δ0,2, lasting quality limit δпр and maximum failure strain Σmax were determined on the basis of the received curves. Initial Remanium GM 700 coupon and consecutively smelted ones were studied in scanning electronic microscope JSM-820 with X-ray microanalysis system Link AN10/85S. Statistical analysis of the received data demonstrated considerable changes in the composition of coupons increasing with the number of smelting. On the one hand, this can be explained with the two-phase nature of the studied alloy. The most significant differences from the nameplate data are fixed for the value of maximum failure strain, since Σmax for the studied coupons remained lower than 1%, while the producer guarantees this value at 4% level. In case of δ0,2 and δпр indices high correspondence of the measured and nameplate values is fixed at least at the primary smelting. Correlation between the abovementioned stretching stress-strain curves and strain type is of great interest. Primary smelting features only type 1 curves, while type 2 curve appears after the third smelting with dominating sixth one. The research involved testing of 10 coupons after each smelting. Presented results of complex studies of mechanical properties of dental casting alloy Remanium GM 700 show their lowering with the increase of smelting quantity. While some coupons after the third smelting demonstrate crumbly features accompanied with significant reduction of strength properties. It should be noted here that the expectation of such alloy behavior is growing with the increase of smelting quantity. It proves the need for careful second use of the alloy for denture casting. No doubt, the reasons of such behavior can be found in structural changes caused by smelting

Keywords

• alloy
• cobalt
• chrome
• nickel
• molybdenum
• smelting