Abstract
The effects of Al coating on the life of engine valve as well as various characteristics of Fe-Al alloy layer formed on valve steel by Al coating were investigated. The results obtained were as follows.(1) The thickness of alloy layer after diffusion heating varied considerably depending on the kind of base steels with the same thickness of sprayed Al layer and other experimental conditions. The thickness of alloy layer on ferritic steel was about twice as large as that of austenitic one.(2) By X-ray diffraction method, it was found that the Al content in alloy layer of austenitic steel was higher than that of ferritic one.(3) The oxidation resistance of valve steel was remarkably improved by Al coating regardless of the kind of steels. However, the rate of improvement in the resistance was greater in ferritic steel than in austenitic one.(4) The corrosion resistance of austenitic Cr-Ni steel to molten PbO was considerably improved by Al coating.(5) The thermal expansion coefficient of alloy layer was almost equal to that of austenitic steel, but it was much greater than that of ferritic one. The crack formation on alloy layer of ferritic steel subjected to the repeated cycles of rapid heating and cooling was caused by the significant difference of expansion coefficients between the alloy layer and the base steel.(6) The hardness of alloy layer was very higher than that of base steel up to 600°C, and it was not so much lowered by heating at 700°C for a long time.(7) It was found by the engine test that Al coating was not so effective for the improvement in the life of inlet valve, but it has considerable effects for the prevention of mechanical and corrosive attacks on exhaust valve, which have been hitherto inevitable.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
