Fabrication and Properties of Plasma-Sprayed Al2O3/ZrO2 Composite Coatings

Abstract

Al 2 O 3 /xZrO 2 (where x = 0, 3, 13, and 20 wt.%) composite coatings were deposited onto mild steel substrates by atmospheric plasma spraying of mixed a-Al 2 O 3 and nano-sized monoclinic-ZrO 2 powders. Microstructural investigation showed that the coatings comprised well-separated Al 2 O 3 and ZrO 2 lamellae, pores, and partially molten particles. The coating comprised mainly of metastable c-Al 2 O 3 and tetragonal-ZrO 2 with trace of original a-Al 2 O 3 and monoclinic-ZrO 2 phases. The effect of ZrO 2 addition on the properties of coatings were investigated in terms of microhardness, fracture toughness, and wear behavior. It was found that ZrO 2 improved the fracture toughness, reduced friction coefficient, and wear rate of the coatings.

Axial Plasma Spraying of Mixed Suspensions: A Case Study on Processing, Characteristics, and Tribological Behavior of Al2O3-YSZ Coatings

“…A previous study on APS Al 2 O 3 -ZrO 2 fine-structured composite coating comprising fine ZrO 2 dispersed in a coarse-structured Al 2 O 3 matrix has been shown to yield better wear resistance and lower friction coefficient compared to a conventional coarse-structured Al 2 O 3 coating [30]. An SPS Al 2 O 3 / ZrO 2 laminated composite coating produced by Berghaus et al [23] yielded a significant improvement in mechanical and thermal performance compared to Al 2 O 3 and ZrO 2 alone, which can be useful for a variety of applications demanding enhanced resistance against abrasion, wear, oxygen diffusion, elevated temperature exposure, etc.…”

Performance of Hybrid Powder-Suspension Axial Plasma Sprayed Al2O3—YSZ Coatings in Bovine Serum Solution

“…The conventional alumina coating Ap exhibited the typical XRD pattern representative of conventional plasma sprayed alumina coatings in which the metastable γ-Al 2 O 3 was observed to be the major phase along with traces of α-Al 2 O 3 phase . It is well known that in conventional plasma spraying, the presence of γ-Al 2 O 3 is attributable to the rapid splat quenching of alumina during the plasma spray process, whereas the α-Al 2 O 3 results from partially melted or unmelted alumina particles [20,21,22,23,24]. On the contrary, the coating As which was produced by the SPS technique showed α-Al 2 O 3 as the predominant phase rather than γ-Al 2 O 3 .…”

“…It was also noted that the suspension derived coating AsYs exhibited the lowest hardness 938 ± 08 HV among all the coatings. A relative decrease in hardness in the cases of ApYs and AsYs compared to Ap and As respectively was due to the inclusion of YSZ, which has an intrinsic lower hardness than alumina [22].…”

Wear studies on plasma-sprayed Al2O3 and 8mole% of Yttrium-stabilized ZrO2 composite coating on biomedical Ti-6Al-4V alloy for orthopedic joint application

“…Because the variables considered for the development of coatings are multilevel variables and their resulting effects are not linearly related, it was decided to test five levels for each variable. The ranges for the variables of input power, spraying distance, and primary gas flow rate were chosen on the basis of literature review 27,28,[33][34][35][36][37] and a large number of experimental trials. Plasma parameters for the experiment and their levels are shown in Table 2.…”

“…As alumina has low fracture toughness, the microhardness, toughness, and wear resistance of the Al 2 O 3 coatings can be further improved by the addition of other oxides like ZrO 2 or TiO 2 . [26][27][28][29][30][31][32] Research on varying the composition of alumina and zirconia has been attempted to develop ceramic balls for orthopedic applications. 32 Further, coatings with 40wt%ZrO 2 on steel and stainless steel substrates developed using the plasma-spray process have led to better tribological results than have other compositions, which has led us to choose this composition for coating in the present study.…”