The influence of sulfur on the oxidation of coatings

An unusual mechanical failure mode in gold ballbonds at 50μm pitch due to degradation at the Au–Au4Al interface during ageing in air at 175°C

“…An additional concern, and one that has not been satisfactorily addressed here or elsewhere in the literature, is the effect of bondpad contaminants on intermetallic growth. Given the very low levels of sulphur on the bondpad it seems unlikely that it is involved in the intermetallic degradation but there should be awareness of the potentially damaging effect of S on various aluminides [24][25][26][27]. While oxidative degradation of the Au 4 Al may be a plausible mechanism for the de-bonding of the ballbonds, it is necessary to formulate a hypothesis for the squash height dependence of the failure mode.…”

“…It is uncertain whether the presence of trace amounts of sulphur have an impact on intermetallic growth and stability in ballbonds. Sulphur at levels of 5-10 ppm by weight causes degradation of [24][25][26][27] and great efforts are made to reduce S levels as well as to dope the alloys with sulphur getters such as yttrium.…”

Characterization of Sulfur Distribution in Ni-Based Superalloy and Thermal Barrier Coatings After High Temperature Oxidation: A SIMS Analysis

“…Many authors have experimentally highlighted the detrimental effect of S on the adherence of oxide scales [1,11,[13][14][15][16], be it on Ni or Fe based alumina or chromia scale forming alloys, after isothermal or cyclic oxidation. Smialek et al [6] have formalized this S-linked oxide scale spalling by identifying a critical S content for maximizing the adherence of alumina on Ni-based superalloys.…”

Evaluation of aluminide diffusion coatings for thermal cyclic oxidation protection of a nickel-base superalloy

“…Sulfur impurities are known to affect scale adherence by segregating at the substrate surface at higher temperatures and causing accelerated scale growth [24,25]. For the cerium modified coating, (Fig.…”

“…From the results reported by Rayner [9] and Ishii and Kawasaki [26], the segregation tendency of yttrium appears to be much stronger than that of cerium. Thus, yttrium can effectively negate the adverse effect of sulfur by binding and immobilizing sulfur through the formation of stable yttrium sulfides [23,24]. With lanthanum addition, the scale is the reaction product of the inward diffusion of oxygen at the scale-coating interface and the interface is renewed continuously.…”