Abstract
Increasing interest for industrial use of thermally sprayed coatings leads to development in most thermal spraying technologies, including atmospheric plasma spraying (APS). The latest cascaded torch SinplexPro from Oerlikon Metco incorporates the efficiency advantages of cascaded arc technology into a single-cathode spray gun. It leads to more stable plasma arc across a wide range of gas flows, mixtures and pressures and also highly increases powder throughput. Thermal sprayed molybdenum coatings are widely used for improving wear resistance and sliding properties in many mechanical applications. Results of pure molybdenum coatings sprayed with cascaded plasma torch are not yet fully investigated. In this paper, mechanical properties of atmospheric plasma sprayed molybdenum coatings on steel (S235) substrate are evaluated. Optimization of spraying parameters for spherical Mo powder sprayed by cascaded plasma torch SinplexPro is carried out and the influence on final microstructure, mechanical and tribological properties of molybdenum coatings is analysed.
Highlights
Atmospheric plasma spraying (APS) technology is widely used for spraying of function layers
Whereas the spraying of pure molybdenum and molybdenum alloys by conventional plasma torches has been closely investigated in the past (e.g. Ref. [2,3,4]), molybdenum spraying with cascaded plasma torch is not yet fully examined
The increase in modulus can be a result of the increase in residual stress, with higher modulus indicating higher compressive stress [11]
Summary
Atmospheric plasma spraying (APS) technology is widely used for spraying of function layers. High temperature is required for melting and consequential efficient deposition of refractory metals, ceramics and cermets. Capability to deposit such materials makes plasma spraying suitable for the production of wear resistant coatings, corrosion protective layers and thermal barriers [1]. Industrial APS with conventional torches is often struggling with reproducibility and reliability [5] This is caused due to the instability of arc and subsequent oscilation of the output power level of the conventional torch during spraying process. Sinplex Pro cascaded torch deals with this issue by stacking copper rings insulated one from each other into a cascade Electric arc developing in such configuration is more stable and reduces almost all problems of conventional torches [5,6,7]
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