engleski

EFFECT OF ALUMINIZING ON SURFACE MICROSTRUCTURE OF AN AUSTENITIC STAINLESS STEEL

In this research, a high temperature thermo- chemical diffusion treatment by aluminization of austenitic stainless steel X5CrNi18-10 (W.Nr. 1.4301, AISI 304) was conducted. Two different aluminizing powder mixtures were tested, at two different process temperatures and process duration time of 6 hours. Aluminization was conducted in a proprietary retort under protective atmosphere of inert argon gas. Aluminizing powders consisted of aluminum fine powder, activators (AlCl3 and NH4Cl) and Al2O3 inert filler (for a sole purpose of prevention of powder sintering at such high temperatures). As expected, this work confirmed formation of high-hardness intermetallics in surface layers of aluminized samples, as well as undeniable correlation between diffusion depth of aluminum in austenitic steel and process parameters in focus (temperature and aluminizing powders composition).The microstructure of the samples was examined by optical microscopy, SEM and EDS. The results show that new, aluminized surfaces consist of two distinguished layers. First layer consists mainly of Fe-Al intermetallic phases, under which the second – interdiffusion layer is formed. This interdiffusion layer consists of CrAl and CrxAl reinforced ferrite. Micro hardness HV0.1 of bulk material and the aluminized surface was determined, as well as aluminized surfaces oxidation resistance.

austenitic stainless steel ; high temperature aluminizing ; oxidation resistance

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