Al-Si-Cr coating was prepared on the surface of 25Cr35 Ni Nb alloy by pack cementation, and its anti-coking properties were studied by coking experiment using ethylene cracking test apparatus. The microstructure of coating and the morphology of coke were investigated with metallurgic microscope, electronic scanning microscope(SEM) and energy dispersive X-ray spectrometer(EDS). Al-Si-Cr coating with thickness of about 130 -m was obtained by pack cementation. The coating had multiple layers with dense structu...