EFFECT OF HEAT TREATMENT ON IMPINGEMENT OF 13/4 MARTENSITIC STAINLESS STEEL

Abstract

In the present study, investigations have been carried out on the effect of various heat treatments on the structure, mechanical properties and erosion behavior of 13Cr-4Ni martensitic stainless steel (CA-6NM) of nominal chemical compositions (weight%): C-0.06% Cr-13.4% Ni-3.9% Mn-1.61% Si-0.74% Mo-0.61 Fe-bal This steel is most widely used in the fabrication of under water parts in the hydroelectric power projects. The present work aims at studies to develop high erosion resistance in the cast steels by giving various heat treatments. The as received samples of the 13Cr-4Ni martensitic stainless steel were given some standard heat treatments. These heat treatments involve the austenisation of as cast steel at temperatures of 950°C, 1000°C and 1050°C and the holding time for each temperature is 4 hrs. This is followed by oil quenching and then tempering at 600°C for 30minutes, 60minutes and 90minutes for each condition. The heat treated steel was tested for toughness, tensile strength, hardness and ductility to study the effect on erosion behavior. The as received and heat treated material at each austenitizing temperature and tempering duration were studied by optical microscope to identify the different micro constituents such as lath martensite, carbides etc. which precipitates along the grain boundaries during the heat treatment. Erosion testing has been done in the erosion tester fabricated at 00, 300, 600, and 900 in slurry containing 16.66% sand at 2515rpm. The mechanisms of erosion have been investigated using Scanning Electron Microscope (SEM). It is observed that at higher impingements angles erosion due to plastic deformation and fragmentation of material and lower impingement angles the erosion predominantly due the cutting action.