بررسی خواص مکانیکی و ریزساختاري ساختار تدریجی فولاد زنگنزن 17-4 و استلایت 6 ساخته شده با فرایند رسوب نشانی مستقیم لیزري

In this study, laser direct deposition was employed to fabricate a functionally graded transition
between 17‑4PH stainless steel and Stellite 6. Specimens were designed and produced such that
the chemical composition varied incrementally from 100% 17‑4PH to 100% Stellite 6, with each
step involving a 25% decrease in the 17‑4PH content and a corresponding 25 % increase in
Stellite 6. Microstructural evolution and elemental distribution were characterized by scanning
electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), while mechanical
properties were assessed via Vickers microhardness testing and uniaxial tensile tests. The
microstructural analysis revealed a needle‑like martensitic matrix in the substrate, which
transformed into cellular dendrites upon reaching the 25% Stellite 6 layer. As the Stellite 6
fraction increased, along with corresponding rises in Cr and W content, grain boundaries
broadened and carbides accumulated within interdendritic regions. At the 50% composition,
oriented columnar dendrites became prominent, and at higher Stellite 6 levels the dendritic
structure refined further, ultimately evolving into an equiaxed morphology. Microhardness
measurements showed a continuous increase from approximately 300 HV in the 17‑4PH substrate
to 490 HV in the pure Stellite 6 layer. Tensile testing demonstrated that both yield strength (σᵧ)
and ultimate tensile strength (σᵤ) remained within 1102–1159 MPa across all compositions, with
no evidence of brittle phases or manufacturing defects. Elongation increased from 7% in pure
Stellite 6 to 19% in pure 17‑4PH, with the 50%–50% gradient exhibiting an optimal balance of
strength and ductility (14.5% elongation).