Effect of shot peening on the oxidation behavior of thermal barrier coatings

The effect of SMAT on pack boronizing of EN8 steel is addressed. SMAT induced plastic deformation, enabled nanocrystallization at the surface, reduced the grain size and increased the volume fraction of non-equilibrium gain boundaries, accumulation of defects and dislocations at the grain boundaries and within the grains. These features helped to promote the diffusion of boron. The present study demonstrates for the first time that SMAT treated EN8 steel can be boronized with a reasonable case depth at 923 K for 7 h. It also addresses the benefits of duplex treatment methodology to achieve the desired case depth and a dense boronized layer. Formation of an FeB phase along with an Fe 2 B phase for SMAT treated EN8 steel has also been reported for the first time. The findings of the study recommend that SMAT can be used as a pretreatment for boronizing of steel, provided necessary precautions are made on boron concentration, to control the volume fraction of the deleterious FeB phase.

Effect of surface mechanical attrition treatment (SMAT) on boronizing of EN8 steel

A theoretical model equation has been derived to relate the growth kinetics of silicide coating with the pack chemical composition and other processing conditions for siliconizing of Mo-TZM (Mo-0.5Ti-0.1Zr-0.02C) alloy to improve its oxidation resistance at high temperatures. A series of experiments conducted with varying pack Si (1-10 wt %) and NH 4 F (2-20 wt %) content, time (1-25 h), and temperature (800-1200°C) confirmed the validity of the model. MoSi 2 was the main coating layer formed during the siliconizing process. Optimum processing conditions were derived for doping of Al in MoSi 2 to form Mo(Si,Al) 2 in the outer layer of the coating.

Relationship Between Pack Chemistry and Growth of Silicide Coatings on Mo-TZM Alloy

Effect of ultrasonic cold forging technology as the pretreatment on the corrosion resistance of MAO Ca/P coating on AZ31B Mg alloy

Surface mechanical attrition treatment (SMAT) is a mechanical peening process used to generate ultrafine grain surfaces on a metal. SMAT was carried out on pure magnesium using different attrition media (zirconia [ZiO2], alumina [Al2O3], and steel balls) to observe the effect on microstructure, surface residual stress, surface composition, and corrosion. Surface contamination from SMAT was characterized using glow discharge optical emission spectroscopy (GDOES). The SMAT process produced a refined grain structure on the surface of Mg but resulted in a region of elemental contamination extending ~10 μm into the substrate, regardless of the media used. Consequently, SMAT-treated surfaces showed an increased corrosion rate compared to untreated Mg, primarily through increased cathodic kinetics. This study highlights the issue of contamination resulting from the SMAT process, which is a penalty that accompanies the significant grain refinement of the surface produced by SMAT. This must be considered if attemp...

Z.D. Xiang

Papers

Shot peening effect on aluminide diffusion coating formation on alloy steels at low temperatures