FEM analysis of crystallization residual stresses in composite Ni-P(B4C) films

The thermo-mechanical behaviour of supported MMC Ni-P(B4C) coatings was studied with a FEM modelling and experimental methods. Crystallization residual stresses in the Ni-P matrix were computed by means of a sub-model technique and were measured with two independent methods: X-ray diffractometry and Vickers indentation. The main conclusions of the FEM simulation are: (i) the matrix is in a tensile stress status and the dispersoid in a compressive one; (ii) the matrix is plasticised; (iii) no appreciable stress gradients as a function of coatings depth are present, except for slight (similar to 5%) variations at the coating surface and at the coating-substrate interface. Experimental residual stresses are consistent and in quantitative agreement with maximum tensile stress values from FEM simulations. The stress distribution predicted by FEM was verified with crack path observations by SEM.