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Microstructure and properties of laser surface alloyed PM austenitic stainless steel

100%

Brytan Z. , Bonek M. , Dobrzański L. A.

Journal of Achievements in Materials and Manufacturing Engineering

2010

tom Vol. 40, nr 1

70-78

Purpose: The purpose of this paper is to analyse the effect of laser surface alloying with chromium on the microstructural changes and properties of vacuum sintered austenitic stainless steel type AISI 316L (EN 1.4404). Design/methodology/approach: Surface modification of AISI 316L sintered austenitic stainless steel was carried out by laser surface alloying with chromium powder using high power diode laser (HPDL). The influence of laser alloying conditions, both laser beam power (between 0.7 and 2.0 kW) and powder feed rate (1.0-4.5 g/min) at constant scanning rate of 0.5m/min on the width of alloyed surface layer, penetration depth, microstructure evaluated by LOM, SEM x-ray analysis, surface roughness and microhardness were presented. Findings: The microstructures of Cr laser alloyed surface consist of different zones, starting from the superficial zone rich in alloying powder particles embedded in the surface; these particles protrude from the surface and thus considerably increase the surface roughness. Next is alloyed zone enriched in alloying element where ferrite and austenite coexists. The following transient zone is located between properly alloyed material and the base metal and can be considered as a very narrow HAZ zone. The optimal microstructure homogeneity of Cr alloyed austenitic stainless steel was obtained for powder feed rate of 2.0 and 4.5 g/min and laser beam power of 1.4 kW and 2 kW. Practical implications: Laser surface alloying can be an efficient method of surface layer modification of sintered stainless steel and by this way the surface chromium enrichment can produce microstructural changes affecting mechanical properties. Originality/value: Application of high power diode laser can guarantee uniform heating of treated surface, thus uniform thermal cycle across treated area and uniform penetration depth of chromium alloyed surface layer.

The influence of silver addition on the microstructure and oxidation behaviour of gamma-TiAl based alloys

80%

Gil A. , Niewolak L. , Czyrska-Filemonowicz A. , Penkalla H. J. , Shemet V. , Singheiser L. , Quadakkers W. J.

tom R. XXII, nr 4

341-344

The aim of this study was to investigate how the beneficial effect of silver addition on the oxidation behaviour of TiAl alloys is correlated with changes in the alloys microstructure. For this purpose the microstructures of the following alloys were compared: Ti-50Al (full lamellar), Ti-50Al (duplex), Ti-48Al-2Cr and Ti-48Al-2Ag. The results showed that silver addition stabilises the gamma-TiAl phase formation at the expense of alpha2-Ti3Al phase.

Celem pracy było zbadanie, czy korzystny wpływ dodatku srebra na wysokotemperaturowe utlenianie stopów TiAl jest wywołany zmianami w mikrostrukturze tych materiałów. W tym celu porównano mikrostrukturę następujących stopów: Ti-50Al, Ti-50Al-2Cr i Ti-50Al-2Cr. Potwierdzono, że dodatek srebra stabilizuje fazę gamma-TiAl i eliminuje fazę alfa2-Ti3Al.