Effect of Recycling Cobalt-Chromium Alloy Powder on Metal-Ceramic Bond Strength and Microstructure

To examine the effects of reusing cobalt-chromium-tungsten-containing alloy powder on metalceramic (MC) bond strength and microstructure.

A total of 30 bar and 9 squareshaped cobalt-chromium frameworks were produced by the conventional lost wax (Group C, [nBar = 10, nSquare = 3]) and selective laser melting (SLM) techniques (Group V [nBar = 10 nSquare = 3] with virgin powder and Group R [nBar = 10, nSquare = 3]) with 25-times-reused powder. X-ray diffraction, scanning electron microscopy (SEM), and oxygen/nitrogen/hydrogen (ONH) analysis were used to evaluate the casting ingot, powder, and framework phase compositions, grain size, and microstructure. Three-point bend tests were used to assess the MC bond strengths. MC bond strength values were compared using one-way ANOVA.

The bond strengths did not show significant differences (P > .05) between Groups C (29.95 ± 4.60), V (31.32 ± 3.44), and R (29.90 ± 5.50). The recycled-alloy powder's grain size (14.1 ± 6.33 μm) was significantly larger than that of the virgin alloy powder (12.24 ± 6.03 μm). Reused alloy powder (25 times) had a greater nitrogen (N) concentration than virgin powder. Groups V and R had similar x-ray diffraction patterns, but the Group R frameworks had porous microstructure.

Reusing cobalt-chromium alloy powder 25 times did not affect the MC bond strength. Recycling the cobalt-chromium alloy powder is advisable.