| The objective of this study is to investigate the correlation between microstructure and the wear resistance of various ferrous blend coatings applicable to cylinder bores. Seven types of ferrous spray powders, two of which were stainless steel powders and the others were blend powders of ferrous powders mixed with Al_2O_3-ZrO_2 powders, were sprayed on a low-carbon steel substrate by atmospheric plasma spraying. Microstructural analysis of the coatings showed that iron oxides were formed in the austenitic (or martensitic) matrix by oxidation during spraying, while Al_2O_3-ZrO_2 oxides were mainly formed in the matrix for the blend coatings. The wear test results revealed that the blend coatings showed the better wear resistance than the ferrous coatings because they contained a number of hard Al_2O_3-ZrO_2 oxides. However, they had rough worn surfaces because of the preferential removal of the matrix and the cracking of oxides during wear. The STS 316 coating showed the slightly worse wear resistance than the blend coatings, but they showed the excellent wear resistance to a counterpart material resulting from homogeneous wear in oxides and matrix due to the smaller hardness difference between them. In order to improve the overall wear properties with consideration of the wear resistance of a counterpart material, the hardness difference between oxides and matrix should be minimized, while the hardness should be maintained up to a certain level by forming an appropriate amount of oxides. |
|
