Friction surfacing is a candidate process for depositing corrosion and wear resistant coatings. Being a solid-state process, it offers several advantages over conventional fusion welding based surfacing process. In the current work, martensitic stainless steel AISI 410 was friction surfaced over mild steel substrates. Coating microstructures were characterized using light microscopy, scanning electron microscopy and Xray diffraction. Coatings in as-deposited condition exhibited a fully martensitic microstructure and were found to be quite hard (with an average hardness of 460 HV). Bend and shear tests indicated excellent coating/substrate bonding. Overall, the current work shows that martensitic stainless steel AISI 410 can be satisfactorily friction surfaced on mild steel.

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Hot deformation behavior of nickel-based superalloy XH 67 (Ni-18.5Cr-4.5Mo-4.5W-3.0Fe-2.5Ti-1.2Al) was investigated in the temperature range of 900°C–1,200°C and in the strain rate range of 10−3–10 s−1. A processing map was generated from the flow stress data. Detailed postdeformation microscopy was carried out to understand the microstructural evolution during hot deformation. Correlation of the kinetic analysis together with microstructural characterization studies was accomplished to identify the rate controlling mechanism. An increase in the fraction of ∑3 boundaries is observed with an increase in the strain rate at 1,150°C. In the temperature range of 1,100°C–1,200°C, discontinued dynamic recrystallization has been identified as the major softening mechanism. Based on the critical analysis of the mechanical data together with microstructural analysis, the safe hot working regime for the XH 67 alloy is established to have a temperature range of 1,100°C–1,200°C and a strain rate range of 10−3 to 5 × 10−2 s−1.

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Additive manufacturing of high gamma prime (γ’) Nickel-based superalloys are challenging due to their hot cracking tendency. This study comprises an understanding of microstructural evolution and mechanical properties of Inconel 939 (IN939) alloy processed via laser powder bed fusion (LPBF). The as-printed samples comprised of columnar grains along the build direction with a pronounced <100> texture resulting in ∼17% lower elastic modulus along the build direction as compared to the builds in transverse orientation. The microstructure consists of cellular and columnar dendrites with segregation of Nb, Ta and Si in the inter-dendritic regions (decorating the cell boundaries). Occurrence of fine (< 50 nm) intra granular carbides in the as printed condition is a unique feature of this microstructure. Heat treatment resulted in dissolution of the dendritic microstructure with precipitation of semi-coherent γ’ (Ni3(Al,Ti)) precipitates (150–200 nm) homogeneously from the matrix resulting in ∼16% enhanced yield strength. The <100> texture is retained even after the solution and aging heat treatment indicating thermal stability of this structure.