Study On AISI321 Austenitic Stainless Steel With Laser Surface Alloying

To strengthen the wear-resistance of AISI321 austenitic stainless steel, the TiC reinforced composite coating was produced by laser surface alloying technology. The microstructure, microhardness and wear resistance of the composite coatings were investigated using MBS optical microscopy, X'pert MPD X-ray diffraction meter, Philips XL30 scanning electron microscopy, HXD-1000 microhardness tester and MM-200 sliding wear tester. The formation mechanism of composite coating has been discussed.Experiment and test show that the composite coating has a fine microstructure; TiC particles distribute in composite coating uniformly, and the composite coating is no pores, cracks and other defects; The composite coating and matrix have a good metallurgical combine. The hardness of the composite coating is up to 450 HV, which is 2.5 times of that of the substrate and the numbers of hardness is a gradient distribution. At room temperature and oil lubricate condition, the sliding wear tests indicate friction coefficient of the composite coating is smaller than the matrix and it is small changing in rates, which demonstrates excellent wear resistance. The weight loss of any alloyed layer is smaller than that of corresponding matrix. The worn surface of the alloying coatings is much smoother than the substrate without grooves, crater, showing that the wear-resistance of the material has been greatly improved by laser surface alloying.After stabilizing treatment, the size of TiC particles in the laser surface alloying coatings is larger than that of before stabilizing treatment. And the hardness is about 400HV, which is twice of the substrate. The wear test results indicate that the weight loss is smaller and the coatings have a more wear resistance than that of before stabilizing treatment.