Angelo A. Carvalho
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Research Subjects
Angelo A. Carvalho has a total of 6 co-authors. Here are the top co-authors by number of shared publications:
- André Paulo Tschiptschin
Metallurgical and materials engineering department, Universidade de São Paulo, Sao Paulo, Brazil, Brazil
1 shared publication - Izabel Fernanda Machado
Surface Phenomena Laboratory, LFS, University of São Paulo, São Paulo 05508-030, Brazil
1 shared publication - Miguel Rubira Danelon
Surface Phenomena Laboratory, LFS, University of São Paulo, São Paulo 05508-030, Brazil
1 shared publication - Newton Kiyoshi Fukumasu
Institute for Technological Research (IPT), University of São Paulo, São Paulo, Brazil
1 shared publication - Roberto Martins Souza
University of São Paulo, Brazil
1 shared publication - Ronnie Rodrigo Rego
Aeronautics Institute of Technology, ITA, São Paulo 12228-900, Brazil
1 shared publication
Latest Publications
- Open Access
Microstructural and Mechanical Characterization of Nb-Doped MoS2 Coatings Deposited on H13 Tool Steel Using Nb-Based Interlayers
Molybdenum disulfide is a 2D material with excellent lubricant properties, resulting from weak van der Waals forces between lattice layers and shear-induced crystal orientation. The low forces needed to shear the MoS2 crystal layers grant the tribological system low coefficients of friction (COF). However, film oxidation harms its efficacy in humid atmospheres, leading to an increased COF and poor surface adhesion, making its use preferable in dry or vacuum conditions. To overcome these challenges, doping MoS2 with elements such as Nb, Ti, C, and N emerges as a promising solution. Nevertheless, the adhesion of these coatings to a steel substrate presents challenges and strategies involving the reduction in residual stresses and increased chemical affinity to the substrate by using niobium-based materials as interlayers. In this study, Nb-doped MoS2 films were deposited on H13 steel and silicon wafers using the pulsed direct current balanced magnetron sputtering technique. Different niobium-based interlayers (pure Nb and NbN) were deposited to evaluate the adhesion properties of Nb-doped MoS2 coatings. Unlubricated scratch tests, conducted at room temperature and relative humidity under a progressive load, were performed to analyze the COF and adhesion of the coating. Instrumented indentation tests were conducted to assess the hardness and elastic modulus of the coatings. The microstructure of the coatings was obtained by Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), and Transmission Electron Microscopy (TEM), with Energy-Dispersive X-Ray Spectroscopy (EDS). Results indicated that niobium doping on MoS2 coatings changes the structure from crystalline to amorphous. Additionally, the Nb concentration of the Nb:MoS2 coating changed the mechanical properties, leading to different cohesive failures by different loads during the scratch tests. Results have also indicated that an NbN interlayer optimally promoted the adhesion of the film. This result is justified by the increase in hardness led by higher Nb concentrations, enhancing the load-bearing capacity of the coating. It is concluded that niobium-based materials can be used to enhance the adhesion properties of Nb-doped MoS2 films and improve their tribological performance.
Open AccessMicrostructural and Mechanical Characterization of Nb-Doped MoS2 Coatings Deposited on H13 Tool Steel Using Nb-Based Interlayers
Molybdenum disulfide is a 2D material with excellent lubricant properties, resulting from weak van der Waals forces between lattice layers and shear-induced crystal orientation. The low forces needed to shear the MoS2 crystal layers grant the tribological system low coefficients of friction (COF). However, film oxidation harms its efficacy in humid atmospheres, leading to an increased COF and poor surface adhesion, making its use preferable in dry or vacuum conditions. To overcome these challenges, doping MoS2 with elements such as Nb, Ti, C, and N emerges as a promising solution. Nevertheless, the adhesion of these coatings to a steel substrate presents challenges and strategies involving the reduction in residual stresses and increased chemical affinity to the substrate by using niobium-based materials as interlayers. In this study, Nb-doped MoS2 films were deposited on H13 steel and silicon wafers using the pulsed direct current balanced magnetron sputtering technique. Different niobium-based interlayers (pure Nb and NbN) were deposited to evaluate the adhesion properties of Nb-doped MoS2 coatings. Unlubricated scratch tests, conducted at room temperature and relative humidity under a progressive load, were performed to analyze the COF and adhesion of the coating. Instrumented indentation tests were conducted to assess the hardness and elastic modulus of the coatings. The microstructure of the coatings was obtained by Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), and Transmission Electron Microscopy (TEM), with Energy-Dispersive X-Ray Spectroscopy (EDS). Results indicated that niobium doping on MoS2 coatings changes the structure from crystalline to amorphous. Additionally, the Nb concentration of the Nb:MoS2 coating changed the mechanical properties, leading to different cohesive failures by different loads during the scratch tests. Results have also indicated that an NbN interlayer optimally promoted the adhesion of the film. This result is justified by the increase in hardness led by higher Nb concentrations, enhancing the load-bearing capacity of the coating. It is concluded that niobium-based materials can be used to enhance the adhesion properties of Nb-doped MoS2 films and improve their tribological performance.