Use object in template part

As of WordPress 5.5 you can pass variables to template parts by passing them in an array to the third argument of get_template_part():

foreach ($categories as $category) {
    get_template_part( 'temp-parts/loop/blcnr_loop', null, [ 'category' => $category ] );
}

These variables will populate an $args variable accessible from the the template:

echo $args['category']->name;