A metallographic
corrosion method for displaying a GCr15 original austenitic
grain boundary comprises adding
picric acid 5g into
distilled water100ml and mixing continuously, then adding
sodium dodecyl
benzene sulfonate 5ml 50% and mixing, finally adding
ferric chloride 2g, and using after placing for 24 hours. A sample is grinded roughly, grinded finely, polished, cleared, dried, immersed into caustic erodent for 2-5 minutes according to normal method under a
quenching tempering condition until etched surface is changed into silver grey, cleaned up through flowing water, cleaned with
alcohol 95%, and dried. If the sample is over-corroded,
polishing paste W0.5-1.0 or metallographic
polishing egent0.5-1.0 is added on silk
polishing cloth, the sample is polished slightly with hands, then cleaned with
alcohol 95%, and dried. According to practical condition, grain
granularity measurement can adopt methods of picture contrast, grid, intercept, quantitative
metallography, and the like, to assess according to relevant standards.