Behavior of HVOF WC-10Co4Cr Coatings with Different Carbide Size in Fine and Coarse Particle Abrasion

A modified ASTM G 65 rubber wheel test was employed in wet and dry conditions using 220 nm titania particles and 368 lm sand particles, respectively. Both tests were conducted on WC-CoCr coatings produced with two powders with different carbide grain sizes (conventional and sub-micron) to address the effect of carbide size and abrasive medium characteristics on the wear performance. The same spot before and after the wet abrasion wear testing was analyzed in detail using SEM to visualize wear mechanisms. It was shown that the wear mechanism depends on the relative size of the carbide and abrasive particles. Wear mechanisms in dry sand abrasion were studied by analyzing the single scratches formed by individual abrasive particles. Interaction of surface open porosity with moving abrasive particles causes formation of single scratches. By tailoring the carbide size, the wear performance can be improved

Effect of aging and solution annealing on transformation and deformation mechanism of super-elastic Ni50.9%-Ti alloy in nano- scale

Effects of aging and solution annealing treatment on the super elastic respond of the cold-worked Ni50.9%-Ti thin wire was studied in nano-scale utilizing instrumented nanoindentation. The nanoindentation results were coupled with the tensile test results to provide better insight to the governing deformation mechanisms. The first applied heat treatment consisted of solution annealing treatment (850°C for 60 minutes) followed by aging at 450°C for 30 minutes and as second heat treatment the cold-worked wire was aged at 450°C for 30 minutes with no prior solution annealing treatment. Both tensile test and nanoindentation results showed better super elastic behavior for the wire subjected to second treatment. Indentation displacement bursts were observed in loading course after both treatments. However, slope changes in unloading course of indents were recorded after second heat treatment which might be due to reverse phase transformation. Surface asperities on the post-indented surface after first treatment were observed far away from indentation stress field by atomic force microscopy