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Treatment of Non-Nickel-based Ceramic Alloys Before Recasting and Effects of Recasting on the Mechanical Properties of the Non-nickel-based Ceramic Alloys

Author: YangSong
Tutor: ChengHui
School: Fujian Medical
Course: Clinical Stomatology
Keywords: Non-nickel-based ceramic alloys Recast Surface treatment Flexural properties Tensile properties Microhardness
CLC: R783.1
Type: Master's thesis
Year: 2011
Downloads: 35
Quote: 5
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Abstract

Objective: The objective of the current study was to find an appropriate method to treat the non-nickel-based ceramic alloys before recasting. The other objective was to investigate the effects of recasting on the mechanical properties of the non- nickel-based ceramic alloys.Materials and Methods: (1) Field emission scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDAX) were used to evaluate the changes in surface structure and composition of non-nickel-based alloys after abrasive blasting and acid etching for different time periods. Meanwhile, In the meantime, the losses in weight after different treatments were recorded using an analytical balance. (2) According to the ISO standard, the non-nickel-based ceramic alloys were cast for 1-3 times using the best pre-cast treatment we found previously. The flexural properties, tensile properties, and microhardness of each specimen were then recorded with a universal testing machine and microhardness tester, respectively.Results: (1) Using different sand blasting methods, and different concentration of chemical solutions to treat metal alloys for different time period, were able to remove the impurities from the surface of alloys to different extents. Further, the weight losses of different alloys were found to be different. Within the limitation of the present study, we found the most appropriate way to treat metal alloys before recast as follows: 1) for CoCr ceramic alloys: aluminum oxide blasting and immersion in aqua regia for 15 min; 2) for CP Ti ceramic alloys: aluminum oxide blasting and immersion in hydrofluoric acid and nitric acid 1:7 (V/V) for 60 min; 3) for Pd-based ceramic alloys: glass bead blasting and immersion in hydrofluoric acid for 30 min; 4) for Au-Pt ceramic alloys: glass bead blasting or aluminum oxide blasting and then immersion in sodium hydrate for 60 min. (2) No significant difference was found on the flexural strength, flexural modulus, tensile strength, 0.2% yield strength, elongation and microhardness of the CoCr ceramic alloys being cast for 2, 3 times, when comparing to those of the alloys being cast for just 1 time (P>0.05). No significant difference was found on the flexural strength of the CP Ti ceramic alloys that had been cast for 2, 3 times, when comparing to that of the alloys being cast for just 1 time (P>0.05). However, the flexural modulus, tensile strength, 0.2% yield strength, surface microhardness of the CP Ti alloys being cast for 2 or 3 times was significantly higher than those of the alloys being cast for 1 time (P<0.05). Elongation of the CP Ti alloys being cast for 2 or 3 times was significantly lower than that of the alloys being cast for 1 time (P<0.05). No significant decrease was found on the tensile strength, 0.2% yield strength, elongation and microhardness of the Pd-based ceramic alloys that had been cast for 2, 3 times, when comparing to that of the alloys being cast for just 1 time (P>0.05). However, the flexural strength, flexural modulus of the Pd-based alloys being cast for 2 or 3 times was significantly lower than that of the alloys being cast for 1 time (P<0.05). No significant difference was found on the flexural strength, tensile strength, 0.2% yield strength, elongation and microhardness of the Au-Pt ceramic alloys that had been cast for 2, 3 times, when comparing to that of the alloys being cast for just 1 time (P>0.05). The flexural modulus of the Au-Pt alloys being cast for 2 or 3 times was significantly higher than that of the alloys being cast for 1 time (P<0.05).Conclusion: (1) Based on the findings of the present study, the most appropriate methods to treat metal alloys before recast were as follows: For CoCr ceramic alloy, aluminum oxide blasting and immersion in aqua regia for 15 min should be applied. For CP Ti ceramic alloy, aluminum oxide blasting and immersion in hydrofluoric acid and nitric acid 1:7 (V/V) for 60min should be used. For Pd-based ceramic alloy, glass bead blasting and immersion in hydrofluoric acid for 30 min should be applied. For Au-Pt ceramic alloy, glass bead blasting or aluminum oxide blasting and then immersion in sodium hydrate for 60 min should be used. (2) The CoCr, Au-Pt ceramic alloy might be cast for 3 times at least without causing any decrease in the flexural properties, tensile properties and microhardness. Recasting might cause decreases in tensile properties and flexural properties of CP Ti ceramic alloy and Pd-based ceramic alloy, respectively.

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