The wear resistance of coated tools is a key technical parameter, which is indirectly affected by the substrate phase characteristics. WC–Co cemented carbides with varied WC grain sizes (0.4, 0.7, 1.2 μm) and Co contents (3, 6, 10, 12 wt.%) were used as the substrates. Single-layer Al_0.52Ti_0.48N and multilayer Ti_0.89Si_0.11N/TiAlSiN/Al_0.52Ti_0.48N films were deposited on the substrates by DC magnetron sputtering. Reciprocating friction tests were carried out in the air medium and the 3.5 wt.% NaCl aqueous solution, respectively. In the air medium, the films on the fine and the submicron WC–Co substrates with the weaker carrying capacity became worn through earlier than those on the ultrafine substrates. In the NaCl solution medium, for the ultrafine-grained WC–10Co substrates with different Co contents, the friction coefficients (F_S) of the film had a linear negative correlation with the hardness (H_S) of the substrates. With the decrease in the WC grain sizes or the Co contents, the wear rates of the coated alloys decreased gradually (by 19.7% and 34.5%, respectively). The regular patterns obtained can provide a reference for the selection and design of the phase composition of the cemented carbide substrates.

5A06 aluminum alloy bar was brazed by temperature gradient transient liquid phase diffusion welding (TG-TLP). The effects of brazing temperature on the microstructure and the tensile strength of the brazing joints were investigated. Three typical brazing filler alloys (1^# Al-20Cu-6Si-2Ni, 2^# Al-10Cu-10Si-3Mg-1Ga, and 3^# Al-6Cu-10Si-2Mg-10Zn) were prepared by smelting, and TG-TLP diffusion bonding was carried out at different brazing temperatures (550 °C~590 °C). The results show that with the increase in brazing temperature, the oxide films at the brazing junction are easier to be broken and dispersed, but the oxidation extent will also increase. The oxidation products enriched were mainly Al₂O₃ and SiO₂ at the brazing junction. There are different optimal brazing temperatures corresponding to the different filler alloys. For 1^#, the optimal temperature is 570 °C; for 2^# is 580 °C; for 3^# is 580 °C. For 1^# brazing joints, the maximum tensile strength was 113 MPa, and for 2^# was 122.4 MPa. Under the experimental conditions of this study, the maximum tensile strength of the TG-TLP joint is 147.4 MPa of 3^# brazing sample (at 580 °C), which has increased by 30% and 20% compared to 1^# and 2^# respectively. The nickel-rich phase at the interface (of 1^# brazing filler) could form a brittle fracture, which was unfavorable for interface bonding. For TG-TLP brazing of 5A06, the filler alloy with high Al:Cu ratio (12:1 wt.%) needs a sufficient temperature gradient to exert the film-breaking effect, while the filler alloy with low Al:Cu ratio (3.6:1 wt.%) needs to accurately control its brazing temperature to avoid excessive oxidation. There are many research gaps in the influence of brazing material composition and brazing temperature on the microstructure and mechanical properties of 5A06 aluminum alloy TG-TLP joints. The research results can provide a theoretical basis for formulating the TG-TLP brazing specification of 5A06 aluminum alloy.

Preparing a highly wear-resistant AlTiN coating on a powder metallurgy (PM) M42 high-speed steel substrate is a key strategy to enhance tool performance and meet the demands of efficient machining. This study adopted a process route comprising substrate preparation, heat treatment regulation, and arc-PVD deposition of AlTiN coatings to systematically investigate the influence of sintering temperature (1130, 1160, and 1190 °C) and austenitizing time (1150 °C for 0, 15, 60, and 120 min) on the microstructure and mechanical properties of the substrate, as well as on the tribological performance of the AlTiN coatings. The results indicate that elevating the sintering temperature promotes densification of the matrix, with Vickers hardness increasing from 366 HV to 462 HV and bending strength (σ) increasing from 1064 MPa to 1310 MPa. The predominant carbide phases identified are MC, M₂C, and M₆C. During austenitizing, microstructural changes consistent with a progressive transformation from M₂C to MC and M₆C carbides were indicated by SEM and XRD analyses. Precipitation strengthening was most evident after 60 min, with hardness reaching 868 HV. In contrast, bending strength (σ) exhibited a progressive decline with increasing austenitizing time, decreasing from 1310 MPa to 1015 MPa after 120 min, illustrating a clear trade-off between hardness and toughness. The wear behavior of the coating is governed synergistically by substrate hardness, bending strength (σ), coating–substrate interfacial adhesion strength (L_C), and carbide phase transformation. Elevated substrate hardness enhances anti-wear performance; bending strength influences crack propagation and spallation tendency; and L_C determines the efficiency of interfacial load transfer. The carbide phase evolution appears to modulate the coating’s wear behavior by regulating both the microstructure and mechanical properties of the substrate. Among the six sample conditions evaluated, the A3 sample (sintered at 1190 °C and austenitized for 120 min) exhibited the lowest wear rate (2.38 × 10⁻⁶ mm³·N⁻¹·m⁻¹), demonstrating superior wear resistance. These findings provide a reference for process optimization and rational design of M42/AlTiN composite coating systems.