Across all industries, material specifications are tightening beyond previously understood process capabilities. Slight shifts in material grade, microstructure, heat treatment, or alloy composition can significantly impact long term material integrity. This study examines the feasibility of noncontact, 100% inline magneto-inductive testing on materials and components to ensure material quality standards. To investigate the hypothesis that material grade, carbon content, density, and alloy composition can be accurately tested in real time during production, an experiment was conducted using magneto-inductive test instrumentation and an encircling coil. The results of the investigation confirmed that 100% of the material in a component could be thus tested, accurately, efficiently, and autonomously verifying that the specified material grade with the proper composition and properties had been used.

Carburization is a common method of hardening steel surfaces to be wear-resistant for a wide range of mechanical processes. One critical characteristic of the carburization process is the increase in carbon content that leads to the formation of martensite in the surface layer. Combustion and spark-OES are two common methods for determination of carbon in steels. However, these techniques do not effectively separate carbon from near surface contaminants, carburized layers, and base material composition. Careful consideration of glow discharge spectroscopy as a method of precisely characterizing carbon concentration in surface layers as part of a production process should be evaluated in terms of how the resulting data align with other common analytical and metallurgical measurements. When used together, glow discharge spectroscopy, optical microscopy, and microhardness testing are all useful, complementary techniques for characterizing the elemental composition, visually observable changes in material composition, and changes in surface hardness throughout the hardened case, respectively. Close agreement between related measurements can be used to support the use of each of these techniques as part of a strong quality program for heat treatment facilities.

Hydrogen embrittlement (HE) susceptibility was investigated for Alloy 718 and Alloy 945X specimens heat treated to a set of conditions within the specifications of API Standard 6ACRA. Heat treatments were selected to simulate the potential variation in thermal history in thick sections of bar or forged products and produce various amounts of discontinuous grain boundary δ phase in Alloy 718 and M 23 C 6 carbides in Alloy 945X, while maintaining a constant hardness in the range of 35-45 HRC for Alloy 718 and 34-42 HRC for Alloy 945X. Time-temperature-transformation (TTT) diagrams and experimentation were used to select a set of heat treatments containing no δ phase, a small quantity of δ, and a larger quantity of δ in Alloy 718. The presence of δ phase has not been verified for the moderate condition. A similar approach was taken regarding M 23 C 6 carbides in Alloy 945X. Incremental step loading (ISL) tests were conducted under in-situ cathodic charging on circular notch tensile (CNT) specimens in a 0.5 M H2SO4 solution. During the test, the direct current potential drop (DCPD) was measured across the notch to determine the stress intensity associated with unstable crack growth. Results indicate that even very small quantities of δ phase in Alloy 718 are detrimental to HE resistance. Both Alloy 718 and Alloy 945X show decreases in HE resistance with aging, with a greater degradation in Alloy 718.

The current Automotive Industry Action Group (AIAG) CQI-9 audit process has limited effectiveness to proactively detect heat treatment quality risks in Tier-1 and Tier-2 supply bases. A cross-functional engineering organization developed an improved supplier audit form using CQI-9, National Aerospace and Defense Contractors Accreditation Program (NADCAP), International Automotive Task Force (IATF), and specific internal company standards to distinguish and quantify production issues that may have been undiscovered with the existing CQI-9 approach. Representatives from engineering, commercial, and manufacturing crafted a more complete approach to supply chain quality. This new audit format (Beyond CQI-9) has demonstrated the ability to quantify heat treatment concerns, reduce future engineering resource costs, and develop new and existing heat treatment suppliers to meet world class quality levels.